Review on Compounds Isolated from Eriocaulaceae Family and Evaluation of Biological Activities by Machine Learning

Eriocaulaceae is a pantropical family whose main center of biodiversity is in Brazil. In general, the family has about 1200 species, in which phytochemical and biological studies have shown a variety of structures and activities. The aim of this research is to compile the compounds isolated in the Eriocaulaceae family and carry out a computational study on their biological targets. The bibliographic research was carried out on six databases. Tables were built and organized according to the chemical class. In addition, a summary of the methods of isolating the compounds was also made. In the computational study were used ChEMBL platform, DRAGON 7.0, and the KNIME 4.4.0 software. Two hundred and twenty-two different compounds have been isolated in sixty-eight species, divided mainly into flavonoids and naphthopyranones, and minor compounds. The ligand-based virtual screening found promising molecules and molecules with multitarget potential, such as xanthones 194, 196, 200 and saponin 202, with xanthone 194 as the most promising. Several compounds with biological activities were isolated in the family, but the chemical profiles of many species are still unknown. The selected structures are a starting point for further studies to develop new antiparasitic and antiviral compounds based on natural products.


Introduction
Eriocaulaceae is a pantropical family, which comprises around 1200 species divided in ten genera [1]. It is easily distinguished from other families due to most of its species presenting short stems, leaves in a rosette form, and long scapes grouped in capitula [2,3].
Brazil is the main center of Eriocaulaceae biodiversity, where there are a total of 610 species, 548 of them being endemic, and distributed in eight genera, with one endemic genus. Some species, belonging to Syngonanthus and Comanthera genera, are economically important, being commercialized as ornamental objects and commonly exported as "everlasting plants." In addition to those, in regions called "campos rupestres," in the states of Bahia, Goiás, Minas Gerais, and Tocantins, the plants that occur naturally are one of the main sources of income for local inhabitants [3][4][5].
Among the genera from Eriocaulaceae, Eriocaulon is the biggest, with 478 species, and the only one with a pantropical distribution. It is an aquatic and wetland genus. In Brazil it occurs in all domains of the country and has 61 known species. The greatest diversity of Eriocaulon is in the Cerrado, where about 80% of species are endemic [6][7][8].
One aglycone (34) and five glycosylated flavonoids (35)(36)(37)(38)(39) were obtained from fresh leaves of Paepalanthus vellozioides and P. latipes after extraction with ethanol and chromatographic procedures. Most compounds have the glycoside group attached to the 3-position of the flavonoid skeleton [24]. Additionally, according to Dokkedal et al. (2008), 34 and 36 were isolated in P. bromelioides and 35 in P. planifolius [22]. Moreira and collaborators (2002) studied the ethanol extract of scapes of the Paepalanthus latipes. Two flavonoids (34 and 36) were isolated, and the mutagenic activity of the metabolites and the crude extract was evaluated against different mutant strains of Moreira and collaborators (2002) studied the ethanol extract of scapes of the Paepalanthus latipes. Two flavonoids (34 and 36) were isolated, and the mutagenic activity of the metabolites and the crude extract was evaluated against different mutant strains of Salmonella typhimurium (TA98 and TA100). None of the flavonoids nor the crude extract showed mutagenic activity induction in bacteria [36]. Eleven years later, another study with aerial parts of the same plant obtained the same metabolites. Antimycobacterial activity was performed against Mycobacterium tuberculosis (H37Rv ATCC 27294) and Mycobacterium avium (ATCC 15769) and showed a low activity of the flavonoids and ethanolic extract [37]. Santos et al. (1999) obtained ethanol extracts from four different species of Paepalanthus: P. hilairei, P. bromelioides, P. vellozioides, and P. latipes. Nine flavonoid metabolites (32, 33, 2, 40, 29, 41, and 42) were obtained after fractionation by droplet countercurrent chromatography (DCCC) followed by column chromatography [38]. Dokkedal et al. (2008) also reported the presence of 32 in P. macropodus and 41 in Leiothrix curvifolia in their review [22]. Salmonella typhimurium (TA98 and TA100). None of the flavonoids nor the crude extract showed mutagenic activity induction in bacteria [36]. Eleven years later, another study with aerial parts of the same plant obtained the same metabolites. Antimycobacterial activity was performed against Mycobacterium tuberculosis (H37Rv ATCC 27294) and Mycobacterium avium (ATCC 15769) and showed a low activity of the flavonoids and ethanolic extract [37]. Santos et al. (1999) obtained ethanol extracts from four different species of Paepalanthus: P. hilairei, P. bromelioides, P. vellozioides, and P. latipes. Nine flavonoid metabolites (32, 33, 2, 40, 29, 41, and 42) were obtained after fractionation by droplet countercurrent chromatography (DCCC) followed by column chromatography [38]. Dokkedal et al. (2008) also reported the presence of 32 in P. macropodus and 41 in Leiothrix curvifolia in their review [22].
The on-line separation and identification of two 6-methoxykaempferol glycosides previously isolated (28 and 33) has been performed with an HPLC-NMR coupling using C-30 phase. Flavonoids were isolated from Paepalanthus ramosus capitula ethanolic extracts [39].
The on-line separation and identification of two 6-methoxykaempferol glycosides previously isolated (28 and 33) has been performed with an HPLC-NMR coupling using C-30 phase. Flavonoids were isolated from Paepalanthus ramosus capitula ethanolic extracts [39].
The on-line separation and identification of two 6-methoxykaempferol glycosides previously isolated (28 and 33) has been performed with an HPLC-NMR coupling using C-30 phase. Flavonoids were isolated from Paepalanthus ramosus capitula ethanolic extracts [39].
The ethyl acetate fraction of Leiothrix flavescens was fractionated by high-speed counter-current chromatography (HSCCC) using the mixture of n-hexane:ethyl acetate:methanol:water, 1:5:1:5 (v/v/v/v). The lower phase of the solvent system was used as a stationary The ethyl acetate fraction of Leiothrix flavescens was fractionated by high-speed countercurrent chromatography (HSCCC) using the mixture of n-hexane:ethyl acetate:methanol: water, 1:5:1:5 (v/v/v/v). The lower phase of the solvent system was used as a stationary phase and the upper one as a mobile phase. Some fractions provided yellow solids identified as flavonoids when sprayed with NP/PEG reagent. The substances were purified in a Sephadex LH-20 column and eluted with methanol. This procedure identified apigenin (10) luteolin (12), and 6-methoxyluteolin (54). The antioxidant activity of methanol extract was evaluated by the DPPH method, showing that the crude extract is more active at a concentration above 80.0 g mL −1 when compared with the acid gallic standard. Phenolic compounds were also quantified by using the Folin-Ciocalteau reagent method. According to the authors, the total phenol concentration in 1.0 g of the methanol extract is 47.0 mg [45].
Molecules 2022, 27, 7186 10 of 56 extract was also examined in the ulcer model ethanol/HCl-induced gastric mucosal lesions, showing a significant inhibition of ulcer formation when compared with the control group [49].
The work carried out by Dokkedal et al. (2007) resulted in the isolation of a dihydroflavonol C-glycoside characterized as xeractinol (65) from a methanol extract of the leaves of Paepalanthus argenteus var. argenteus. Xeractinol was isolated after eluting from a Sephadex LH-20 column with MeOH and showed a yellow spot on TLC under UV light [50].
The work carried out by Dokkedal et al. (2007) resulted in the isolation of a dihydroflavonol C-glycoside characterized as xeractinol (65) from a methanol extract of the leaves of Paepalanthus argenteus var. argenteus. Xeractinol was isolated after eluting from a Sephadex LH-20 column with MeOH and showed a yellow spot on TLC under UV light [50].
Molecules 2022, 27, 7186 10 of 56 extract was also examined in the ulcer model ethanol/HCl-induced gastric mucosal lesions, showing a significant inhibition of ulcer formation when compared with the control group [49].
The work carried out by Dokkedal et al. (2007) resulted in the isolation of a dihydroflavonol C-glycoside characterized as xeractinol (65) from a methanol extract of the leaves of Paepalanthus argenteus var. argenteus. Xeractinol was isolated after eluting from a Sephadex LH-20 column with MeOH and showed a yellow spot on TLC under UV light [50].
Methanol extract of Eriocaulon ligulatum capitula was submitted to liquid chromatography-electrospray ionization multistage ion trap mass spectrometry (LC-ESI-IT-MS n ). As a result, the authors identified 3, 10, 12, 54, 59, and 76-81 based on their fragmentation patterns in MS experiments and on NMR analysis for isolated compounds [55].
Methanol extract of Eriocaulon ligulatum capitula was submitted to liquid chromatographyelectrospray ionization multistage ion trap mass spectrometry (LC-ESI-IT-MS n ). As a result, the authors identified 3, 10, 12, 54, 59, and 76-81 based on their fragmentation patterns in MS experiments and on NMR analysis for isolated compounds [55]. The compounds 6-methoxyapigenin (10), 6-methoxyapigenin-7-O-β-D-glucopyranoside (17), and rutin (82) were quantified by using high performance liquid chromatography with DAD detection in methanolic extracts of capitula of Syngonanthus suberosus, S. dealbatus, Eriocaulon ligulatum, and capitula and leaves of Leiothix spiralis, in time intervals of less than 7 min. The identification was made by comparing the retention times with those of standards, by adding standard solutions to the samples analyzed by HPLC, and by comparing their UV-Vis spectrum. All extracts were tested against six strains of microorganism, inhibiting the growth of all the tested microorganisms [56].
The compounds 6-methoxyapigenin (10), 6-methoxyapigenin-7-O-β-D-glucopyranoside (17), and rutin (82) were quantified by using high performance liquid chromatography with DAD detection in methanolic extracts of capitula of Syngonanthus suberosus, S. dealbatus, Eriocaulon ligulatum, and capitula and leaves of Leiothix spiralis, in time intervals of less than 7 min. The identification was made by comparing the retention times with those of standards, by adding standard solutions to the samples analyzed by HPLC, and by comparing their UV-Vis spectrum. All extracts were tested against six strains of microorganism, inhibiting the growth of all the tested microorganisms [56].
noside (17), and rutin (82) were quantified by using high performance liquid chromatography with DAD detection in methanolic extracts of capitula of Syngonanthus suberosus, S. dealbatus, Eriocaulon ligulatum, and capitula and leaves of Leiothix spiralis, in time intervals of less than 7 min. The identification was made by comparing the retention times with those of standards, by adding standard solutions to the samples analyzed by HPLC, and by comparing their UV-Vis spectrum. All extracts were tested against six strains of microorganism, inhibiting the growth of all the tested microorganisms [56].
An analytical study was carried out with scapes and flowers of Syngonanthus nintens to define the metabolite fingerprint by HPLC-ESI-MS n . Additionally, the methanolic extracted of both scapes and flowers were filtered and fractionated on a Sephadex LH-20 column, using MeOH as mobile phase. Other separation procedures were performed to isolate 12, 45, 47, 56, and 83-90 from scapes. The structures of all compounds were elucidated by NMR spectroscopic data [57]. The in vitro antioxidant properties of the S. nintens methanolic extract were evaluated by electron paramagnetic resonance (EPR) spectroscopy based on their ability to scavenge the DPPH radical. The kinetics of reaction between DPPH and S. nintens was determined. Luteolin (12) and isoorientin (47) were also used to investigate kinetics of reaction between DPPH and flavonoids. As a result, S. nitens showed a high antioxidant capacity the authors attributed to the presence of flavonoids, and 47 presented an antioxidant activity 40% higher than 12 [58].
An analytical study was carried out with scapes and flowers of Syngonanthus nintens to define the metabolite fingerprint by HPLC-ESI-MS n . Additionally, the methanolic extracted of both scapes and flowers were filtered and fractionated on a Sephadex LH-20 column, using MeOH as mobile phase. Other separation procedures were performed to isolate 12, 45, 47, 56, and 83-90 from scapes. The structures of all compounds were elucidated by NMR spectroscopic data [57]. The in vitro antioxidant properties of the S. nintens methanolic extract were evaluated by electron paramagnetic resonance (EPR) spectroscopy based on their ability to scavenge the DPPH radical. The kinetics of reaction between DPPH and S. nintens was determined. Luteolin (12) and isoorientin (47) were also used to investigate kinetics of reaction between DPPH and flavonoids. As a result, S. nitens showed a high antioxidant capacity the authors attributed to the presence of flavonoids, and 47 presented an antioxidant activity 40% higher than 12 [58]. An ethanolic extract from scapes of Syngonanthus macrolepis yielded a flavonoid-rich fraction after going through a Sephadex LH-20 chromatographic column, containing luteolin (12), 7-methoxyluteolin-6-C-β-D-glucopyranoside (45), luteolin-6-C-β-D-glucopyranoside (47), 6-hydroxyluteolin (56), and 7,3′-dimethoxyluteolin-6-C-β-D-glucopyranoside (88) identified after HPLC purification. A flavonoid-rich fraction was investigated for preventing gastric ulceration in mice and rats, showing a significant reduction in gastric injury in all models tested, without altering gastric juice parameters after pylorus ligation [59].
A methanolic extract of Leiothrix spiralis leaves was chromatographed on a Sephadex LH-20 column with MeOH as eluent. After separation of three fractions by medium pressure liquid chromatography (MPLC), five flavonoids (44, 45, 47, 87, and 91) were found. Minimum inhibitory concentration (MIC) analysis revealed antibacterial and/or antifungal activity for all compounds [60].
A methanolic extract of Leiothrix spiralis leaves was chromatographed on a Sephadex LH-20 column with MeOH as eluent. After separation of three fractions by medium pressure liquid chromatography (MPLC), five flavonoids (44, 45, 47, 87, and 91) were found. Minimum inhibitory concentration (MIC) analysis revealed antibacterial and/or antifungal activity for all compounds [60].
Methanolic extracts from powdered capitula and scapes of Paepalanthus chiquitensis Herzog were fractioned in Sephadex LH-20 using MeOH as eluent. A fraction from a mentioned procedure of capitula yielded the pure compound 28. A fraction from scapes was separated by semi-preparative HPLC-IR yielding the new compound, 113. Compound 120 was also isolated from both capitula and scapes. Other compounds such as 28, 76, and 114 were identified by HPLC-ESI-MS n using external standard and compounds 80, 110-112, and 115-119 according to m/z and literature. A Salmonella/microsome biological assay was performed with methanolic extracts, resulting in mutagenic activity against the TA97a strain [64].
Methanolic extracts of capitula and scapes of Syngonanthus dealbatus, S. macrolepsis, S. nitens, and S. suberosus were separated with Sephadex LH-20. Fractions of scapes column were also separated in HSCCC. Compounds 45 and 87 were purified by HPLC-UV and 12, 56, and 88 by HPLC-RID. The mutagenicity of extracts and isolated compounds were evaluated, but none of them showed activity. All isolated flavones could also be used as new antimutagenic agents [63].
Methanolic extracts from powdered capitula and scapes of Paepalanthus chiquitensis Herzog were fractioned in Sephadex LH-20 using MeOH as eluent. A fraction from a mentioned procedure of capitula yielded the pure compound 28. A fraction from scapes was separated by semi-preparative HPLC-IR yielding the new compound, 113. Compound 120 was also isolated from both capitula and scapes. Other compounds such as 28, 76, and 114 were identified by HPLC-ESI-MS n using external standard and compounds 80, 110-112, and 115-119 according to m/z and literature. A Salmonella/microsome biological assay was performed with methanolic extracts, resulting in mutagenic activity against the TA97a strain [64]. The hydroethanolic extract of the aerial parts from Tonina fluviatilis was submitted to different methods of separation to yield 6-methoxyquercetin-3-O-β-D-glucopyranoside (30), 6-hydroxy-7-methoxyquercetin-3-O-β-D-glucopyranoside (35), and 6,7-dimethoxyquercetin-3-O-β-D-glucopyranoside (121). After obtaining the compounds and elucidating their structures, they were quantified in the extracts by using HPLC-DAD. The radical scavenging activity was also performed to extract and isolate compounds, showing a better result for compounds 30 and 35 [1].
After the isolation of a new compound named as paepalantine (131) from a chloroform extract of Paepalanthus bromelioides capitula [69], many other studies were performed with species from Paepalanthus genus.
After the isolation of a new compound named as paepalantine (131) from a chloroform extract of Paepalanthus bromelioides capitula [69], many other studies were performed with species from Paepalanthus genus.
Besides Paepalanthus bromelioides, compound 131, paepalantine, was also isolated from P. vellozioides following Vilegas et al.'s (1990) separation procedure. Mutagenic and cytotoxic activities were tested against Salmonella typhimurium TA100, TA98, and TA102, and McCoy cells using the Neutral Red (NR) and microculture tetrazolium (MTT) techniques, respectively. Paepalantine showed mutagenic effect both in the absence and the presence of metabolic activation and also showed a IC 50 equivalent to 30 and 38 mg mL −1 for NR and MTT, respectively [70]. In 1999, Tavares et al. [71] evaluated the clastogenic effect of compound 131, with negative result, but observed significant cytotoxic activity when testing the compound in vitro and in vivo mammalian cell systems. The intestinal antiinflammatory activity of compound 131 was also evaluated, resulting in paepalantine significantly attenuating the colonic damage induced by trinitrobenzenesulphonic acid (TNBS) both when colonic mucosa is intact or when the mucosa is recovering after an initial insult [72]. A study on the influence of dimethylsulfoxide (DMSO) in its antioxidant activity was also performed showing that DMSO significantly interfered with the hypochlorous acid (HOCl) assay, but propylene glycol may be the solvent of choice for paepalantine [73].
activity was also performed showing that DMSO significantly interfered with the hypochlorous acid (HOCl) assay, but propylene glycol may be the solvent of choice for paepalantine [73].
Compounds 131 and 132 were also isolated from Paepalanthus acanthophyllus. The supernatant of methanol extract was fractioned in Sephadex LH-20 column and the fractions were filtered in SPE RP-18 cartridge. After chromatographic profile by HPLC-PDA, a chosen fraction was submitted to separation in a semipreparative HPLC-PDA, leading to isolation of both 131 and 132 [65]. Compound 132 was also isolated from P. planifolius [75].
When evaluating the cytotoxicity of the three naphthopyranones against McCoy cells using neutral red assays [76], 131-133 showed a significant cytotoxic index when compared with the IC50 value of cisplatin, a cytotoxic substance used in antineoplasic therapy. When tested for antimicrobial activity using a spectrophotometric microdilution technique, 131 was active against Syngonanthus aureus, S. epidermidis, and Eriocaulon faecalis whereas 132 and 133 proved ineffective against all microorganisms tested [77]. Leitão et al. (2002) also isolated compounds 131-133 in the same Paepalanthus bromelioides extract by HSCCC and evaluated their antioxidant activity. As a result, 131 showed good antioxidant activity in the DPPH radical assay [78]. Moreira et al. (2013) also isolated compound 133 and assessed the antimycobacterial activity using the Alamar Blue TM (MABA) method disqualifying the naphthopyranone 133 as a promising candidate against Mycobacterium tuberculosis and M. avium [37].
Compounds 131 and 132 were also isolated from Paepalanthus acanthophyllus. The supernatant of methanol extract was fractioned in Sephadex LH-20 column and the fractions were filtered in SPE RP-18 cartridge. After chromatographic profile by HPLC-PDA, a chosen fraction was submitted to separation in a semipreparative HPLC-PDA, leading to isolation of both 131 and 132 [65]. Compound 132 was also isolated from P. planifolius [75].
When evaluating the cytotoxicity of the three naphthopyranones against McCoy cells using neutral red assays [76], 131-133 showed a significant cytotoxic index when compared with the IC 50 value of cisplatin, a cytotoxic substance used in antineoplasic therapy. When tested for antimicrobial activity using a spectrophotometric microdilution technique, 131 was active against Syngonanthus aureus, S. epidermidis, and Eriocaulon faecalis whereas 132 and 133 proved ineffective against all microorganisms tested [77]. Leitão et al. (2002) also isolated compounds 131-133 in the same Paepalanthus bromelioides extract by HSCCC and evaluated their antioxidant activity. As a result, 131 showed good antioxidant activity in the DPPH radical assay [78]. Moreira et al. (2013) also isolated compound 133 and assessed the antimycobacterial activity using the Alamar Blue TM (MABA) method disqualifying the naphthopyranone 133 as a promising candidate against Mycobacterium tuberculosis and M. avium [37].
The crude MeOH extracts of Paepalanthus vellozioides and P. latipes leaves, after purification with Amberlite XAD-2 followed by Sephadex LH-20 column, produced a crude glycosidic mixture, which was separated by reverse-phase HPLC, to yield pure compounds 134, 135, and 136. Their structures were determined by spectroscopic and spectrometric techniques [23]. Additionally, the naphthopyranones 134 and 136 were identified in aerial parts of Actinocephalus divaricatus by high-resolution orbitrap mass spectrometry [79]. Compounds 134, 135, and 136 were also isolated in the whole Eriocaulon buergerianum species [53].  [43] identified the compound by spectroscopic methods and compared it to those previously reported.
The crude MeOH extracts of Paepalanthus vellozioides and P. latipes leaves, after purification with Amberlite XAD-2 followed by Sephadex LH-20 column, produced a crude glycosidic mixture, which was separated by reverse-phase HPLC, to yield pure compounds 134, 135, and 136. Their structures were determined by spectroscopic and spectrometric techniques [23]. Additionally, the naphthopyranones 134 and 136 were identified in aerial parts of Actinocephalus divaricatus by high-resolution orbitrap mass spectrometry [79]. Compounds 134, 135, and 136 were also isolated in the whole Eriocaulon buergerianum species [53].
Vioxanthin (142), a yellow-green powder, was isolated for the first time from acetone extracts of Paepalanthus falcifolius Koern., P. albovaginatus Alv. Silv., P. argenteus Koern., P. cuspidatus Alv. Silv., and P. ramosus Kunth. According to Provost and Garcia (1990), vioxanthin is very common in fungi of Tricophyton genus. However, those species studied were collected in different regions of Brazil and the plants showed no detectable contamination by microorganisms. Thus, this was the first isolation from a plant source [85]. Vioanthin was also found in P. bromelioides capitula CH2Cl2 extract and in P. planifolius ca-Vioxanthin (142), a yellow-green powder, was isolated for the first time from acetone extracts of Paepalanthus falcifolius Koern., P. albovaginatus Alv. Silv., P. argenteus Koern., P. cuspidatus Alv. Silv., and P. ramosus Kunth. According to Provost and Garcia (1990), viox-anthin is very common in fungi of Tricophyton genus. However, those species studied were collected in different regions of Brazil and the plants showed no detectable contamination by microorganisms. Thus, this was the first isolation from a plant source [85]. Vioanthin was also found in P. bromelioides capitula CH 2 Cl 2 extract and in P. planifolius capitula EtOAc extract [75]. Furthermore, effects of compounds 131, 141, and 142 on mitochondria were evaluated [86,87].
Vioxanthin (142), a yellow-green powder, was isolated for the first time from acetone extracts of Paepalanthus falcifolius Koern., P. albovaginatus Alv. Silv., P. argenteus Koern., P. cuspidatus Alv. Silv., and P. ramosus Kunth. According to Provost and Garcia (1990), vioxanthin is very common in fungi of Tricophyton genus. However, those species studied were collected in different regions of Brazil and the plants showed no detectable contamination by microorganisms. Thus, this was the first isolation from a plant source [85]. Vioanthin was also found in P. bromelioides capitula CH2Cl2 extract and in P. planifolius capitula EtOAc extract [75]. Furthermore, effects of compounds 131, 141, and 142 on mitochondria were evaluated [86,87].
Eriocauline (143) is a naphthopyranone dimer isolated from Eriocaulon ligulatum capitula. The dichloromethane extracts were submitted to column chromatography on silica gel and their structure was identified by spectroscopic and spectrometric experiments [51].
Three other compounds, 144, 145, and 146, were characterized from Eriocaulon ligulatum capitula. The methanolic extract was analyzed by liquid chromatography electrospray ionization multistage ion trap mass spectrometry (LC-ESI-IT-MS n ). All three compounds were identified based on their fragmentation patterns in MS and in NMR spectra. This was the first report of 144 and 145 in Eriocaulon genus [55]. Additionally, compound 146 was isolated in the whole E. buergerianum [53] and in Paepalanthus denudatus and P. speciosus [22,52].
Eriocauline (143) is a naphthopyranone dimer isolated from Eriocaulon ligulatum capitula. The dichloromethane extracts were submitted to column chromatography on silica gel and their structure was identified by spectroscopic and spectrometric experiments [51].
Vioxanthin (142), a yellow-green powder, was isolated for the first time from acetone extracts of Paepalanthus falcifolius Koern., P. albovaginatus Alv. Silv., P. argenteus Koern., P. cuspidatus Alv. Silv., and P. ramosus Kunth. According to Provost and Garcia (1990), vioxanthin is very common in fungi of Tricophyton genus. However, those species studied were collected in different regions of Brazil and the plants showed no detectable contamination by microorganisms. Thus, this was the first isolation from a plant source [85]. Vioanthin was also found in P. bromelioides capitula CH2Cl2 extract and in P. planifolius capitula EtOAc extract [75]. Furthermore, effects of compounds 131, 141, and 142 on mitochondria were evaluated [86,87].
Eriocauline (143) is a naphthopyranone dimer isolated from Eriocaulon ligulatum capitula. The dichloromethane extracts were submitted to column chromatography on silica gel and their structure was identified by spectroscopic and spectrometric experiments [51].
Three other compounds, 144, 145, and 146, were characterized from Eriocaulon ligulatum capitula. The methanolic extract was analyzed by liquid chromatography electrospray ionization multistage ion trap mass spectrometry (LC-ESI-IT-MS n ). All three compounds were identified based on their fragmentation patterns in MS and in NMR spectra. This was the first report of 144 and 145 in Eriocaulon genus [55]. Additionally, compound 146 was isolated in the whole E. buergerianum [53] and in Paepalanthus denudatus and P. speciosus [22,52].
Paepalanthus geniculatus Kunth. flowers were submitted to HPLC-ESI-MS n analysis after the methanol extract showed radical-scavenging activity in the Trolox equivalent antioxidant capacity (TEAC) assay. Two known naphthopyranones (149, 150) and two new ones (151, 152) were isolated. In antioxidant assay, compounds 151 and 152 showed the highest TEAC values [61]. The naphthopyranones 151 and 152 were identified in aerial parts of Actinocephalus divaricatus by high-resolution orbitrap mass spectrometry [79].
Paepalanthus geniculatus Kunth. flowers were submitted to HPLC-ESI-MS n analysis after the methanol extract showed radical-scavenging activity in the Trolox equivalent antioxidant capacity (TEAC) assay. Two known naphthopyranones (149, 150) and two new ones (151, 152) were isolated. In antioxidant assay, compounds 151 and 152 showed the highest TEAC values [61]. The naphthopyranones 151 and 152 were identified in aerial parts of Actinocephalus divaricatus by high-resolution orbitrap mass spectrometry [79].
Paepalanthus geniculatus Kunth. flowers were submitted to HPLC-ESI-MS n analysis after the methanol extract showed radical-scavenging activity in the Trolox equivalent antioxidant capacity (TEAC) assay. Two known naphthopyranones (149, 150) and two new ones (151, 152) were isolated. In antioxidant assay, compounds 151 and 152 showed the highest TEAC values [61]. The naphthopyranones 151 and 152 were identified in aerial parts of Actinocephalus divaricatus by high-resolution orbitrap mass spectrometry [79].
The methanol extracts of Paepalanthus chiquitensis capitula and scapes were subm to HPLC-ESI-IT-MS n to characterization. In capitula, the naphthopyranones 132, 146 and 155 were identified, whereas, in scapes, 146 and 154 were identified [64]. Comp 155 was also isolated from Actinocephalus divaricatus (Korn.) Sano ; 145, 148, 153, and 164-166 in E. buergerianum; 145, 148, 153, and 164-166 in E. cine  and 148, 153, and 164-166 in E. faberi. In short, they found thirty-six naphthopyranones isolated from one species of Actinocephalus, five species of Eriocaulon, and twenty-one species of Paepalanthus, being four aglycones, twenty-one glycones, and eleven dimers. The dimers were isolated in Paepalanthus and Eriocaulon at the positions C-8, C-9, and C-10. The glycosylation pattern occurs only at the C-9 position, with a binding between the naphthopyranone and α-glucose or β-glucose being very common. When the binding is between a naphthopyranone and a disaccharide, the glucoside unit starts with a glucose. The sugars forming disaccharides In short, they found thirty-six naphthopyranones isolated from one species of Actinocephalus, five species of Eriocaulon, and twenty-one species of Paepalanthus, being four aglycones, twenty-one glycones, and eleven dimers. The dimers were isolated in Paepalanthus and Eriocaulon at the positions C-8, C-9, and C-10. The glycosylation pattern occurs only at the C-9 position, with a binding between the naphthopyranone and α-glucose or β-glucose being very common. When the binding is between a naphthopyranone and a disaccharide, the glucoside unit starts with a glucose. The sugars forming disaccharides with glucose are glucose, rhamnose, arabinose, and allose. Table 2 shows the names of naphthopyranones, the part of the plant where they were isolated, species, and authors.  Leaves P. latipes [23] Aerial parts Actinocephalus divaricatus [79] Whole plant E. buergerianum

Compounds Isolated from Eriocaulaceae Fungi
Living plants are colonized by plenty of micro-organisms [89]. Endophytic fungi are microorganisms that inhabit internal plant tissues and provide benefits to the host [90]. They may produce equal or analogous metabolites as their host plants with potential application in many agricultural and industrial segments, which increased many scientists' interests in studying potential biologically active compounds [91]. Amorim et al. (2016) isolated endophytic fungi from Paepalanthus planifolius capitula, scapes, and leaves [92]. After treatment for fungus proliferation, fifteen single fungal strains were obtained and one of them was identified as Anthostomella brabeji. A. brabeji was submitted to liquid-liquid partition with ethyl acetate, resulting in a crude extract. The ethyl acetate extract was purified by semipreparative HPLC-DAD, leading to the isolation of four compounds: new natural product 167 (6.1 mg), 168 (19.4 mg), 169 (9.7 mg), and 170 (13.6 mg). The isolated compounds and EtOAC extract were assayed against the microorganisms Candida albicans, Escherichia coli, Salmonella setubal, and Staphylococcus aureus. strains were obtained and one of them was identified as Anthostomella brabeji. A. brabeji was submitted to liquid-liquid partition with ethyl acetate, resulting in a crude extract. The ethyl acetate extract was purified by semipreparative HPLC-DAD, leading to the isolation of four compounds: new natural product 167 (6.1 mg), 168 (19.4 mg), 169 (9.7 mg), and 170 (13.6 mg). The isolated compounds and EtOAC extract were assayed against the microorganisms Candida albicans, Escherichia coli, Salmonella setubal, and Staphylococcus aureus. Measured MIC values ranged from 31.25 μg mL −1 to 1000.0 μg mL −1 . Hilário et al. (2017), studying aerial parts of Paepalanthus chiquitensis, isolated the endophytic fungi Fusarium fujikuroi and found the ethyl acetate extract was bioactive against Gram-positive bacteria Staphylococcus aureus, Gram-negative Escherichia coli and Salmonella setubal, and the fluconazole-resistant yeast Candida albicans. This chemical study yielded an alkaloid 2-(4-butylpicolinamide) acetic acid (171) and three known compounds: fusaric acid (172), indole acetic acid (173), and terpestacin (174). The minimal inhibitory concentration of the extract, fusaric acid, and indole acetic acid had values from 125 to 1000 μg mL −1 [93].
Three years after the first study on metabolites isolated from endophytic fungi of Paepalanthus planifolius, Amorim et al. (2019) isolated three new benzaldehyde derivatives, sporulosaldeins A-C (175-177), and three new benzopyran derivatives, sporulosaldeins D-F (178-180) from Paraphaeosphaeria sp. F03 in P. planifolius leaves. All isolated compounds had their chemical structure elucidated by nuclear magnetic resonance experiments and high-resolution mass spectrometry analysis. The cytotoxic MCF-7 and LM3 cells and antimicrobial activities were also tested [94].
strains were obtained and one of them was identified as Anthostomella brabeji. A. brabeji was submitted to liquid-liquid partition with ethyl acetate, resulting in a crude extract. The ethyl acetate extract was purified by semipreparative HPLC-DAD, leading to the isolation of four compounds: new natural product 167 (6.1 mg), 168 (19.4 mg), 169 (9.7 mg), and 170 (13.6 mg). The isolated compounds and EtOAC extract were assayed against the microorganisms Candida albicans, Escherichia coli, Salmonella setubal, and Staphylococcus aureus. Measured MIC values ranged from 31.25 μg mL −1 to 1000.0 μg mL −1 . Hilário et al. (2017), studying aerial parts of Paepalanthus chiquitensis, isolated the endophytic fungi Fusarium fujikuroi and found the ethyl acetate extract was bioactive against Gram-positive bacteria Staphylococcus aureus, Gram-negative Escherichia coli and Salmonella setubal, and the fluconazole-resistant yeast Candida albicans. This chemical study yielded an alkaloid 2-(4-butylpicolinamide) acetic acid (171) and three known compounds: fusaric acid (172), indole acetic acid (173), and terpestacin (174). The minimal inhibitory concentration of the extract, fusaric acid, and indole acetic acid had values from 125 to 1000 μg mL −1 [93].
Three years after the first study on metabolites isolated from endophytic fungi of Paepalanthus planifolius, Amorim et al. (2019) isolated three new benzaldehyde derivatives, sporulosaldeins A-C (175-177), and three new benzopyran derivatives, sporulosaldeins D-F (178-180) from Paraphaeosphaeria sp. F03 in P. planifolius leaves. All isolated compounds had their chemical structure elucidated by nuclear magnetic resonance experiments and high-resolution mass spectrometry analysis. The cytotoxic MCF-7 and LM3 cells and antimicrobial activities were also tested [94].
Continuing their studying on aerial parts, [95] isolated the endophytic fungus Curvularia lunata of Paepalanthus chiquitensis capitula. The EtOAc extract (1.3 g) obtained from C. lunata was fractionated by Sephadex LH-20 column chromatography and eluted with Three years after the first study on metabolites isolated from endophytic fungi of Paepalanthus planifolius, Amorim et al. (2019) isolated three new benzaldehyde derivatives, sporulosaldeins A-C (175-177), and three new benzopyran derivatives, sporulosaldeins D-F (178-180) from Paraphaeosphaeria sp. F03 in P. planifolius leaves. All isolated compounds had their chemical structure elucidated by nuclear magnetic resonance experiments and high-resolution mass spectrometry analysis. The cytotoxic MCF-7 and LM3 cells and antimicrobial activities were also tested [94].
strains were obtained and one of them was identified as Anthostomella brabeji. A. brabeji was submitted to liquid-liquid partition with ethyl acetate, resulting in a crude extract. The ethyl acetate extract was purified by semipreparative HPLC-DAD, leading to the isolation of four compounds: new natural product 167 (6.1 mg), 168 (19.4 mg), 169 (9.7 mg), and 170 (13.6 mg). The isolated compounds and EtOAC extract were assayed against the microorganisms Candida albicans, Escherichia coli, Salmonella setubal, and Staphylococcus aureus. Measured MIC values ranged from 31.25 μg mL −1 to 1000.0 μg mL −1 . Hilário et al. (2017), studying aerial parts of Paepalanthus chiquitensis, isolated the endophytic fungi Fusarium fujikuroi and found the ethyl acetate extract was bioactive against Gram-positive bacteria Staphylococcus aureus, Gram-negative Escherichia coli and Salmonella setubal, and the fluconazole-resistant yeast Candida albicans. This chemical study yielded an alkaloid 2-(4-butylpicolinamide) acetic acid (171) and three known compounds: fusaric acid (172), indole acetic acid (173), and terpestacin (174). The minimal inhibitory concentration of the extract, fusaric acid, and indole acetic acid had values from 125 to 1000 μg mL −1 [93].
Three years after the first study on metabolites isolated from endophytic fungi of Paepalanthus planifolius, Amorim et al. (2019) isolated three new benzaldehyde derivatives, sporulosaldeins A-C (175-177), and three new benzopyran derivatives, sporulosaldeins D-F (178-180) from Paraphaeosphaeria sp. F03 in P. planifolius leaves. All isolated compounds had their chemical structure elucidated by nuclear magnetic resonance experiments and high-resolution mass spectrometry analysis. The cytotoxic MCF-7 and LM3 cells and antimicrobial activities were also tested [94].
Continuing their studying on aerial parts, [95] isolated the endophytic fungus Curvularia lunata of Paepalanthus chiquitensis capitula. The EtOAc extract (1.3 g) obtained from C. lunata was fractionated by Sephadex LH-20 column chromatography and eluted with In short, those compounds isolated from Eriocaulaceae family derived from acetylenic phenols, acids, alkaloids, benzaldehydes, benzopyran, chromanones, and sesterpenes. Most of them were isolated from endophytic fungi present in aerial parts of three different species of Paepalanthus. Table 3 shows that information. In short, those compounds isolated from Eriocaulaceae family derived from acetylenic phenols, acids, alkaloids, benzaldehydes, benzopyran, chromanones, and sesterpenes. Most of them were isolated from endophytic fungi present in aerial parts of three different species of Paepalanthus. Table 3 shows that information.

Xanthones
A xanthone skeleton is planar, with a conjugated ring system A and B linked to a carbonyl group and an oxygen atom. They are classified as oxygenated xanthones, prenylated xanthones, xanthone glycosides, bis-xanthones, xanthonolignoids, miscellaneous xanthones, and polyphenolic xanthones are also divided into subclasses depending upon the degree of oxygenation. According to the literature, about 650 xanthones are known from natural sources and diverse biological activities are described for this class [96].
In Eriocaulaceae, seventeen xanthones were isolated, all hydroxylated and with at least one methoxyl group in their structure. Santos et al.    cinereum and E. faberi. The xanthone 193 was also found, but the authors did not specify in which species [67]. None of the isolated compounds showed mutagenicity against the Salmonella typhimurium TA100, TA98, TA97a, and TA102 strains but all of them showed antimutagenic potential [63]. Xanthone 199, 1,5,7-trihydroxy-3,6-dimethoxyxanthone, was identified in methanol extract of S. nitens capitula by performing co-injection experiments in HPLC-PDA [33]. Fang et al. (2008) isolated 191 (36.0 mg), 192 (52.0 mg), and 193 (60.0 mg) from Eriocaulon buergerianum EtOAc extract after successive separation with polyamide and silica gel chromatography. Their structures were determined by spectroscopic methods. All compounds were tested against the pathogenic bacteria Staphylococcus aureus (ATCC 25923), but those xanthones showed no significant antibacterial activity [53]. cinereum and E. faberi. The xanthone 193 was also found, but the authors did not specify in which species [67].  cinereum and E. faberi. The xanthone 193 was also found, but the authors did not specify in which species [67].  Table 4 shows the names of xanthones, the part of the plant where they were isolated, species, and authors.  Table 4 shows the names of xanthones, the part of the plant where they were isolated, species, and authors.

Saponins
Saponins are bioorganic compounds with at least one glycosidic linkage at C-3. The aglycone portion, called genin, sapogenin, or aglycone, may be composed of triterpenoid, steroid, or alkaloid. Triterpenoid saponin kind is the most widely distributed skeleton in the plant kingdom. The glycoside moiety may be composed of both hexoses and pentoses with different conformations. The lipophilic and hydrophilic composition of saponins confer a surfactant action, making saponins a class of metabolites with economic importance. The literature describes saponins' biologic activities such as antibacterial, antitumoral, antifungal, anti-inflammatory, antiviral, insecticidal, etc. [98]. Zanatta et al. (2018) conducted the first study on the chemical composition and biological activity of the aerial parts of Actinocephalus divaricatus [79]. To make a fingerprint of methanolic extract, the authors chose to use a dereplication approach based on Liquid Chromatography coupled to High-Resolution Mass Spectrometry (HPLC-ESI-HRMSMS) as an analytical tool for the screening and structural determination.
Eight saponins were identified based on the fragmentation pattern and compared to literature data. The saponins 202-209 were identified in Actinocephalus divaricatus scapes and 204-208 in the leaves. A known nortriterpenoid saponin 3-O-β-D-glucuronopyranosyl-30-norolean-12,20(29)-dien-28-O-β-D-glucopyranosyl ester (205) was isolated and had its structure determined by MS/MS and NMR experiments and the data were compared with those published in the literature. Besides the mentioned compounds, others were identified but they could not be drawn.
Molecules 2022, 27,7186 43 of 56 Table 5 shows the names of saponins, the part of the plant where they were isolated, species, and authors.  Table 5 shows the names of saponins, the part of the plant where they were isolated, species, and authors.

Steroids
Steroids are complex lipophilic four-ringed organic molecules that act in the body to regulate cellular, tissue, and organ functions [99].

Steroids
Steroids are complex lipophilic four-ringed organic molecules that act in the body to regulate cellular, tissue, and organ functions [99].
In 2008, Song et al. [100] described for the first time a phytochemical study on Eriocaulon sieboldianum (Eriocaulaceae), an aquatic annual herb of Korea, Japan, China, and Africa. Three stigmastane-skeleton sterols were isolated from the ethyl acetate soluble fraction of whole plant and the chemical structures were determined by spectroscopic and spectrometric techniques as IR, MS, and NMR. The isolated compounds were identified as one new compound, stigmasta-7,22-dien-3β,4β-diol (210), and two known compounds, stigmasterol 3-O-β-D-glucopyranoside (211) and stigmasta-5-en-3β-ol (β -sitosterol, 212). Table 6 shows the names of steroids, the part of the plant where they were isolated, species, and authors.

Quinones
Quinones are a large class of natural organic compounds and may be divided into three main groups: benzoquinone, naphthoquinone, and anthraquinone, with this last group as the most common cycle. Currently, more than 2000 quinones are known in nature, found in fungi, lichens, gymnosperms, and angiosperms. In families such as Rubiaceae, Fabaceae, and Boraginaceae, isolating quinones is very common [25], but according to the literature, only two quinones were isolated in Eriocaulaceae. Kitagawa et al. (2004) [101] isolated for the first time the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin (213) from Paepalanthus latipes capitula methylene chloride ex- Table 6 shows the names of steroids, the part of the plant where they were isolated, species, and authors.

Quinones
Quinones are a large class of natural organic compounds and may be divided into three main groups: benzoquinone, naphthoquinone, and anthraquinone, with this last group as the most common cycle. Currently, more than 2000 quinones are known in nature, found in fungi, lichens, gymnosperms, and angiosperms. In families such as Rubiaceae, Fabaceae, and Boraginaceae, isolating quinones is very common [25], but according to the literature, only two quinones were isolated in Eriocaulaceae. Kitagawa et al. (2004) [101] isolated for the first time the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin (213) from Paepalanthus latipes capitula methylene chloride extract. The cytotoxic evaluation showed a significant cytotoxic index of 35.8 mg mL −1 when compared with cisplatin (IC 50 41.9 mg mL −1 ), a cytotoxic substance used in antineoplasic therapy. Kitagawa carried out other biological assessment tests over the years, such as antitumor, immunomodulatory [102], antioxidant, anti-helicobacter pylori activity [103], and mutagenic [104].
In 2008, Fang and co-workers isolated, from an ethyl acetate fraction of the whole Eriocaulon buergerianum, the anthraquinone emodin (214). An antibacterial assay performed with the standard Staphylococcus aureus strain (ATCC 25923) showed a MIC 32 µg mL −1 [53].  Table 7 shows the names of anthraquinone, the part of the plant where they were isolated, species, and authors.

Phenolic Acid Derivatives
Phenolic or phenolcarboxylic acids are one of the main classes of plant phenolic compounds. They are found in a variety of plants and are mainly divided into two sub-groups: hydroxybenzoic and hydroxycinnamic acid. Phenolic acids are known for diverse biological applications such as antidiabetic, anticancer, neuro protective, and food preservative and skin care products [105].
One colorless and amorphous caffeic acid derivative, 3-di-E-caffeoylglycerol 220, was isolated from the ethanolic extract of Paepalanthus microphyllus capitula. The structure of 220 was characterized by spectroscopic and spectrometry methods [46]. Table 7 shows the names of anthraquinone, the part of the plant where they were isolated, species, and authors.

Phenolic Acid Derivatives
Phenolic or phenolcarboxylic acids are one of the main classes of plant phenolic compounds. They are found in a variety of plants and are mainly divided into two sub-groups: hydroxybenzoic and hydroxycinnamic acid. Phenolic acids are known for diverse biological applications such as antidiabetic, anticancer, neuro protective, and food preservative and skin care products [105].
In 2012, studying the same species, Qiao et al. identified 216, 218, and caffeic acid (219) from the 70% methanol extract by HPLC-DAD-ESI-MS n [67].  Table 7 shows the names of anthraquinone, the part of the plant where they were isolated, species, and authors.

Phenolic Acid Derivatives
Phenolic or phenolcarboxylic acids are one of the main classes of plant phenolic compounds. They are found in a variety of plants and are mainly divided into two sub-groups: hydroxybenzoic and hydroxycinnamic acid. Phenolic acids are known for diverse biological applications such as antidiabetic, anticancer, neuro protective, and food preservative and skin care products [105].
One colorless and amorphous caffeic acid derivative, 3-di-E-caffeoylglycerol 220, was isolated from the ethanolic extract of Paepalanthus microphyllus capitula. The structure of 220 was characterized by spectroscopic and spectrometry methods [46].
One colorless and amorphous caffeic acid derivative, 3-di-E-caffeoylglycerol 220, was isolated from the ethanolic extract of Paepalanthus microphyllus capitula. The structure of 220 was characterized by spectroscopic and spectrometry methods [46].
One colorless and amorphous caffeic acid derivative, 3-di-E-caffeoylglycerol 220, was isolated from the ethanolic extract of Paepalanthus microphyllus capitula. The structure of 220 was characterized by spectroscopic and spectrometry methods [46].
The methanolic extract from Leiothrix flavescens capitula was partitioned with EtOAc and submitted to separation by HSCCC. Afterwards, a fraction was chromatographed with Sephadex LH-20 to yield 1,3-O-diferuloilglicerol 221. The structure of 221 was characterized by spectroscopic and spectrometry methods [106].
The methanolic extract from Leiothrix flavescens capitula was partitioned with EtOAc and submitted to separation by HSCCC. Afterwards, a fraction was chromatographed with Sephadex LH-20 to yield 1,3-O-diferuloilglicerol 221. The structure of 221 was characterized by spectroscopic and spectrometry methods [106].  Table 8 shows the names of phenolic acids derivatives, the part of the plant where they were isolated, species, and authors.

Tocopherol
The EtOAc fraction of Eriocaulon buergerianum Koern. capitula was chromatographed in a silica gel column. A fraction after the mentioned procedure was separated by MPLC to yield γ-tocopheryl acetate 222. The structure of 222 was established by spectral methods [44].

Ligand-Based Virtual Screening
The Random Forest algorithm (RF) models were generated following the five-fold cross validation procedure [107,108]. Table 9 shows the statistical performances for each model.  Table 8 shows the names of phenolic acids derivatives, the part of the plant where they were isolated, species, and authors.

Tocopherol
The EtOAc fraction of Eriocaulon buergerianum Koern. capitula was chromatographed in a silica gel column. A fraction after the mentioned procedure was separated by MPLC to yield γ-tocopheryl acetate 222. The structure of 222 was established by spectral methods [44].  Table 8 shows the names of phenolic acids derivatives, the part of the plant where they were isolated, species, and authors.

Tocopherol
The EtOAc fraction of Eriocaulon buergerianum Koern. capitula was chromatographed in a silica gel column. A fraction after the mentioned procedure was separated by MPLC to yield γ-tocopheryl acetate 222. The structure of 222 was established by spectral methods [44].

Ligand-Based Virtual Screening
The Random Forest algorithm (RF) models were generated following the five-fold cross validation procedure [107,108]. Table 9 shows the statistical performances for each model. Table 9. Summary of the parameters of the results obtained in the RF models.

Models
Parasitic

Ligand-Based Virtual Screening
The Random Forest algorithm (RF) models were generated following the five-fold cross validation procedure [107,108]. Table 9 shows the statistical performances for each model. The performance characteristics of the nine models created revealed their predictive power and reliability, and the Receiver Operating Characteristic (ROC) curve and Matthews Correlation Coefficient (MCC) gave information on their performance and robustness.
The Eriocaulaceae dataset with a total of 222 compounds was reduced to 206 molecules (16 structures with undefined sugar units were removed for virtual screening analysis) and analyzed in each model.
In each model, we analyzed the applicability domain (APD) for each molecule to consider its prediction, that is, molecules within the APD of the model have reliable predictions and outside the APD have unreliable predictions. Table 10 shows a summary of how many molecules were inside the APD of each model, and how many of these molecules have an active potential prediction against parasites that cause neglected diseases.  Table 11 shows that for the model against Trypanosoma cruzi parasitic form Trypomastigote, no molecule that remained inside the APD showed active potential. In the T. cruzi-amastigote model only two molecules were predicted to be active out of the 158 molecules that were inside the APD and in the Leishmania infantum-amastigote model only eight molecules were predicted to be active out of the 200 that were inside the APD. The Leishmania infantum-promastigote model had the highest active prediction potential, with molecules reaching a 96% probability of being active. Table 11 shows the five molecules with the highest active potential for the models created.
Analyzing the predictions of molecules isolated from Eriocaulaceae, we can observe that some molecules have multitarget potential, capable of being active for different parasites.
The dataset built in this review with compounds isolated from Eriocaulaceae was used to predict the potential activity against neglected diseases.
For all structures, SMILES (Simplified Molecular Input Line Entry System) codes were used as input data for Marvin 18.10.0, 2018 (ChemAxon) [112] and Standardizer software (JChem 18.10.0, 2018; ChemAxon) [112] to convert the chemical structures into curated and canonical representations. This standardization is of paramount importance to create consistent compound libraries and is done by the following steps: addition of hydrogens, aromatization, generation of 3D structure, and exporting the compounds in SDF format. For a more detailed description on how the dataset was curated, please refer to the workflows described by Fourches et al. [113][114][115].

DRAGON 7.0 Descriptors
Molecular descriptors are used to calculate the physicochemical properties of the molecules from each molecule set. To obtain the molecular descriptors, the DRAGON 7.0 program [116] was used. The DRAGON 7.0 software can calculate 5270 molecular descriptors, covering various approaches. These molecular descriptors are arranged in 30 logical blocks [116].

Random Forest Model
The KNIME 4.4.0 software (KNIME version number 4.4.0, the Konstanz Information Miner Copyright, 2003-2021, Zurich, Switzerland) [117] was used to perform the analyses and to generate the in silico model. Datasets of molecules, along with their calculated descriptors and class variables, were imported from DRAGON 7.0 software. Each dataset was divided using the "partitioning" tool, with the "stratified sample" option, to create a training set and an external test set, which represented 80% and 20% of the compounds, respectively. Although the compounds were selected randomly, the same proportion of active and inactive samples was maintained in both sets.
For external validation, we employed five-fold cross-validation [107,108] using randomly selected, stratified groups, meaning that the entire data set was partitioned five times into a modeling set (training set) including 80% of the compounds in the set, and the external cross validation data set, comprising the remaining 20% of the compounds in the data set. After this, only the modeling set was used to build the models and then the models were validated with the external cross validation technique. Descriptors were selected and modeled following a five-fold external cross validation procedure using the RF [107,108]. A total of 100 parameters were selected for RF for all generated models, which is the number of trees constructed, and 1550953075932 seeds generated random numbers for the model. By using KNIME nodes, the most important descriptors in generating each prediction model were evaluated. The external performances of the selected models were analyzed for sensitivity (true positive rate, i.e., active rate), specificity (true negative rate, i.e., inactive rate), and accuracy (overall predictability). The positive (PPV) and negative (NPV) predictive values inform us about the probability of predicted positives (PPV) and negatives (NPV) being the true positives and negatives, respectively. The sensitivity and specificity of the ROC curve were also found to describe true performance with more clarity than accuracy.
The model was also analyzed by the Matthews coefficient, a way to evaluate the model globally from the results obtained from the confusion matrix. The MCC is a correlation coefficient between observed and predictive binary classifications. It results in a value between −1 and +1, where a coefficient of +1 represents a perfect forecast, 0 is a random forecast, and −1 indicates total disagreement between forecast and observation [118].
The MCC can be calculated from the following formula: where VP is the true positive value, VN is the true negative value, FP is the value of false positives, and FN is the value of false negatives.
The APD was used to analyze the compounds of the test sets to evaluate whether their predictions were reliable. The APD is based on Euclidean distances, and similarity measures between the descriptors of the training set are used to define the applicability domain. Thus, if a test set compound has distances and similarity beyond this limit, its prediction is unreliable.
The APD calculation is performed by using the formula: where d and σ are the Euclidean distances and the standard mean deviation, respectively, of the compounds in the training set. Z is an empirical cut-off value. In this work, the Z value used was 0.5 [119,120].
Many of these compounds had their in vitro biological activities tested, and their mutagenic, antimicrobial, antioxidant, anti-inflammatory, antitumor, and other activities were confirmed.
The computational study showed that the molecules isolated from the Eriocaulaceae family have active potential against neglected diseases: leishmaniasis, schistosomiasis, Chagas disease, and dengue fever. Finding promising molecules with multitarget potential, which were xanthones 194, 196, and 200 and saponin 202, was also possible, with xanthone 194 as the most promising of them.
These data present the relevance of this review, which shows the structural variation of the compounds isolated in the family and in vitro and in vivo biological activities carried out so far and highlights the possibility of new compounds being known, given the number of species that have not been chemically studied. In addition, the chemical and biological knowledge of a species can contribute to the preservation of the species, an important fact, since many Eriocaulaceae species are at risk of extinction.