Search Results (71)

In this study, we combined automated annotation tools with targeted dereplication based on MS/MS fragmentation pathway studies to identify polycyclic polyprenylated acylphloroglucinols (PPAPs) in Hypericum species, using H. patulum and H. hookeranium as a case study. These species, extensively used in traditional medicine, exhibit morphological similarities that often result in misidentification. Following UHPLC-HRMS/MS analysis of plant extracts, a molecular network approach facilitated a comprehensive comparison of their chemical composition, assigning specific clusters to O-glycosylated flavonoids and PPAPs. Eight peaks, including quercitrin, isoquercitrin, procyanidins, chlorogenic acid, quercetin, and glycosylated derivatives, were annotated from the GNPS database. For PPAPs, despite the structural complexity posing challenges for automated annotation using public databases, our targeted-dereplication strategy, relying on in-house spectral data, led to the putative identification of 22 peaks for H. patulum and H. hookeranium. Key compounds such as hyperforin, hyperscabrone K, and garcinialliptone M were detected in both species, underscoring their chemical similarity. MS/MS fragmentation pathways, particularly the successive losses of isobutene and isoprenyl units, emerged as a consistent signature for PPAP detection and may be useful for selecting PPAP-enriched extracts or fractions for further phytochemical investigations. Full article

Glycosylation is a critical enzymatic modification that involves the attachment of sugar moieties to target compounds, considerably influencing their physicochemical and biological characteristics. This review explored the role of two primary enzyme classes—glycosyltransferases (GTs) and glycoside hydrolases (GHs, glycosidases)—in catalyzing the glycosylation of natural products, with a specific focus on Ganoderma triterpenoids. While GTs typically use activated sugar donors, such as uridine diphosphate glucose, certain GHs can leverage more economical sugar sources, such as sucrose and starch, through transglycosylation. This paper also reviewed strategies for producing novel terpenoid glycosides, particularly recently isolated bacterial GTs and GHs capable of glycosylating terpenoids and flavonoids. It summarized the newly synthesized glycosides’ structures and biotransformation mechanisms, enhanced aqueous solubility, and potential applications. The regioselectivity and substrate specificity of GTs and GHs in catalyzing O-glycosylation (glucosylation) at distinct hydroxyl and carboxyl groups were compared. Furthermore, a special case in which the novel glycosylation reactions were mediated by GHs, including the formation of unique glycoside anomers, was included. The advantages and specific capabilities of GT/GH enzymes were evaluated for their potential in biotechnological applications and future research directions. Novel fungal triterpenoid glycosides produced through various glycosidases and sugars is expected to expand their potential applications in the future. Full article

Panax quinquefolius is a globally valued medicinal plant rich in bioactive flavonoids, yet the molecular mechanisms underlying their biosynthesis remain poorly understood. In this study, we integrated transcriptomic and metabolomic analyses to investigate tissue-specific flavonoid accumulation and regulatory networks in roots, leaves, and flowers. Metabolomic profiling identified 141 flavonoid metabolites, with flavones, flavonols, and C-glycosylflavones predominantly enriched in aerial tissues (leaves and flowers), while specific glycosides like tricin 7-O-acetylglucoside showed root-specific accumulation. Transcriptome sequencing revealed 15,551–18,946 DEGs across tissues, and the reliability of the transcriptomic data was validated by qRT-PCR. KEGG and GO annotation analyses suggested that these DEGs may play a crucial role in the biosynthesis and metabolism of secondary metabolites. From the DEGs, UGTs and MYB TFs were identified and subjected to correlation analysis. Functional validation through in vitro enzymatic assays confirmed that PqUGT71A1 catalyzes apigenin and naringenin glycosylation at the 7-OH position. Additionally, subcellular localization and yeast one-hybrid assays demonstrated that PqMYB7 and PqMYB13 interact with the PqUGT71A1 promoter and activate its expression.. This study unveils the spatial dynamics of flavonoid metabolism in P. quinquefolius and establishes a MYB-UGT regulatory axis, providing critical insights for metabolic engineering and bioactive compound optimization in medicinal plants. Full article

The petals of flowering plants should retain unique antioxidants that have not been found in the fruits, as the petals need to stay open to attract pollinators against photooxidation and devise a solution to avoid eating attacks. We reported that the yellow petals of freesia cultivars (Freesia x hybrida) accumulated original apocarotenoids, mono- and di-neapolitanosyl crocetin. Here, in the yellow petals, we discovered eight novel flavonoids by their structural determination, including four 3′-caffeoylquercetin 3,7-glycosides, one 3′-caffeoylquercetin 3-glycoside, and three 4′-caffeoylkaempferol 3,7-glycosides. The 3-carbon sugar part was a minor hexose dimer [D-glucosyl-D-glucoside or D-glucosyl-L-rhamnoside] with the β1,2-linkage, while the 7-carbon was usually O-glycosylated with D-glucose, L-rhamnose, or D-glucuronic acid. Such caffeoyl-flavonol glycosides were also present in freesia white petals, regardless of the cultivars and wild species. When dihydroflavonols, the last common precursors between flavonols and anthocyanins, switch to the flavonol route, these caffeoyl-flavonol glycosides are likely to be synthesized via quercetin or kaempferol. All the eight flavonoids exerted in vitro antioxidant activities against both lipid peroxidation and radical generation. Specifically, 3′-caffeoylquercetin 3-sophoroside and its 7-glucuronide showed superior antioxidant activity. Freesia yellow and white flowers have been utilized as edible flowers, indicating the importance of evaluating the human benefits and risks of newly identified flavonoids. Full article

The bioaccessibility of flavonoids is of paramount importance in determining their bioavailability and biological effects. Bioaccessibility is influenced by several aspects, comprising the food matrix and the structure of flavonoids. In the present study, the bioaccessibility of different classes of flavonoids (flavanones, flavones, and flavonols) was investigated after in vitro gastro-intestinal digestion of beverages and vegetables. O-glycosylated flavanones were stable during in vitro digestion and easily released from the food matrix. Otherwise, C-glycosylated flavanones displayed a lower bioaccessibility index. Similarly, flavones exhibited a high bioaccessibility index in beverages and vegetables, with the O-glycosylated forms being more stable than the C-glycosylated. Flavonols displayed different stability under gastro-intestinal conditions depending on their structure. The presence of a catechol moiety in the B-ring, as observed in 3-O-glycosylated quercetins, negatively impacted flavonol stability in comparison with kaempferol derivatives that lack the catechol moiety. Indeed, the presence of more than one sugar or the glycosylation of the OH group in the B-ring improved the digestive stability of quercetin derivatives. For flavonols, a clear food matrix effect was observed by comparing the bioaccessibility in beverages and vegetable foods. These findings may aid in improving the comprehension of the biological effects of flavonoids and flavonoid-rich foods. Full article

Carob leaves have gained attention for their bioactive properties and traditional medicinal uses, including as treatment for diabetes, digestive disorders, and microbial infections. The aim of this study was to explore the phytochemical composition of carob leaf acetone extracts using advanced spectroscopic techniques. The combined use of heteronuclear nuclear magnetic resonance (NMR) experiments with 1D selective nuclear Overhauser effect spectroscopy (NOESY) offers detailed structural insights and enables the direct identification and quantification of key bioactive constituents in carob leaf extract. In particular, the NMR and mass spectrometry techniques revealed the presence of myricitrin as a predominant flavonoid, as well as a variety of glycosylated derivatives of myricetin and quercetin, in acetone extract. Furthermore, siliquapyranone and related gallotannins are essential constituents of the extract. The potent inhibitory effects of the carob leaf extract on Staphylococcus aureus (MIC = 50 μg mL⁻¹) and a-glucosidase enzyme (IC₅₀ = 67.5 ± 2.4 μg mL⁻¹) were also evaluated. Finally, the antibacterial potency of carob leaf constituents were calculated in silico; digalloyl-parasorboside and gallic acid 4-O-glucoside exert a stronger bactericidal activity than the well-known myricitrin and related flavonoids. In summary, our findings provide valuable insights into the bioactive composition and health-promoting properties of carob leaves and highlight their potential for pharmaceutical and nutraceutical applications. Full article

Chalcones, including 4′-hydroxychalcones, have garnered significant attention in the area of drug discovery due to their diverse pharmacological properties, such as anti-inflammatory, antioxidative, and anticancer effects. However, their low water solubility and bioavailability limit their efficacy in vivo. Glycosylation presents a promising approach to enhance the water solubility, stability, and metabolic properties of chalcones. This study investigates the enzymatic glycosylation of eight chemically synthesized 4′-hydroxychalcones using a diverse set of sugar glucosyltransferases from bacterial, plant, and fungal sources, alongside Glycine max sucrose synthase (GmSuSy) in a cascade reaction. Among the tested enzymes, five exhibited a remarkable versatility for glycoside production, and for large-scale biotransformation, flavonoid 7-O-glucosyltransferase Sbaic7OGT from Scutellaria baicalensis was selected as the most effective. As a result of the experiments conducted, eight trans-chalcone glycosides were obtained. During the purification of the reaction products, we also observed the isomerization of the products by simple sunlight exposure, which resulted in eight additional cis-chalcone glycosides. This study highlights the novel use of a cascade reaction involving Glycine max sucrose synthase (GmSuSy) for the efficient glycosylation of trans-4′-hydroxychalcones, alongside the unexpected discovery of cis-chalcone glycosides during the purification process. Full article

Xanthohumol (1) is a major prenylated flavonoid in hops (Humulus lupulus L.) which exhibits a broad spectrum of health-promoting and therapeutic activities, including anti-inflammatory, antioxidant, antimicrobial, and anticancer effects. However, due to its lipophilic nature, it is poorly soluble in water and barely absorbed from the gastrointestinal tract, which greatly limits its therapeutic potential. One method of increasing the solubility of active compounds is their conjugation to polar molecules, such as sugars. Sugar moiety introduced into the flavonoid molecule significantly increases polarity, which results in better water solubility and often leads to greater bioavailability. Entomopathogenic fungi are well known for their ability to catalyze O-glycosylation reactions. Therefore, we investigated the ability of selected entomopathogenic filamentous fungi to biotransform xanthohumol (1). As a result of the experiments, one aglycone (2) and five glycosides (3–7) were obtained. The obtained (2″E)-4″-hydroxyxanthohumol 4′-O-β-D-(4‴-O-methyl)-glucopyranoside (5) has never been described in the literature so far. Interestingly, in addition to the expected glycosylation reactions, the tested fungi also catalyzed chalcone–flavanone cyclization reactions, which demonstrates chalcone isomerase-like activity, an enzyme typically found in plants. All these findings undoubtedly indicate that entomopathogenic filamentous fungi are still an underexploited pool of novel enzymes. Full article

Rhododendron simsii Planchon is an important ornamental species in the northern hemisphere. Flower color is an important objective of Rhododendron breeding programs. However, information on anthocyanin synthesis in R. simsii is limited. In this research, the regulatory mechanism of anthocyanin biosynthesis in R. simsii was performed through the integrated analysis of metabolome and RNA-seq. A total of 805 and 513 metabolites were screened by positive and negative ionization modes, respectively, In total, 79 flavonoids contained seven anthocyanidins, 42 flavanones, 10 flavans, 13 flavones, and seven flavonols. Methylated and glycosylated derivatives took up the most. Differentially accumulated metabolites were mainly involved in “flavone and flavonol biosynthesis”, “cyanoamino acid metabolism”, “pyrimidine metabolism”, and “phenylalanine metabolism” pathways. For flavonoid biosynthesis, different expression of shikimate O-hydroxycinnamoyltransferase, caffeoyl-CoA O-methyltransferase, flavonoid 3′-monooxygenase, flavonol synthase, dihydroflavonol 4-reductase/flavanone 4-reductase, F3′5′H, chalcone synthase, leucoanthocyanidin reductase, and 5-O-(4-coumaroyl)-D-quinate 3′-monooxygenase genes ultimately led to different accumulations of quercetin, myricetin, cyanidin, and eriodictyol. In flavone and flavonol biosynthesis pathway, differential expression of F3′5′H, flavonoid 3′-monooxygenase and flavonol-3-O-glucoside/galactoside glucosyltransferase genes led to the differential accumulation of quercetin, isovitexin, and laricitrin. This research will provide a biochemical basis for further modification of flower color and genetic breeding in R. simsii and related Rhododendron species. Full article

Glycosylation is one of the most common and important modifications in natural products (NPs), which can alter the biological activities and properties of NPs, effectively increase structural diversity, and improve pharmacological activities. The biosynthesis of glycosylation in natural products involves multiple complex biological processes, which are coordinated by many enzymes. UDP-glycosyltransferases (UGTs) play a crucial role in glycosylation modification, and have attracted long-term and widespread research attention. UGTs can catalyze the O-, C-, S-, and N-glycosylation of different substrates, producing a variety of glycosides with broad biological activity, while improving the solubility, stability, bioavailability, pharmacological activity, and other functions of NPs. In recent years, the rapid development of synthetic biology and advanced manufacturing technologies, especially the widespread application of artificial intelligence in the field of synthetic biology, has led to a series of new discoveries in the biosynthesis of NP glycosides by UGT. This work summarizes the latest progress and challenges in the field of NP glycosylation, covering the research results and potential applications of glycosylated derivatives of terpenes, flavonoids, polyphenols, aromatic compounds, and other compounds in terms of biogenesis. Looking to the future, research may leverage artificial intelligence-driven synthetic biology techniques to decipher genes related to the synthetic pathway, which is expected to further promote the large-scale synthesis and application of glycosylated NPs, and increase the diversity of NPs in the pharmaceutical, functional food, and cosmetic industries. Full article

Zika virus (ZIKV) is involved in the etiology of serious nervous system pathologies. Currently, there are no specific and effective vaccines or antiviral drugs to prevent the diseases caused by ZIKV. This study aimed to assess the activity of flavonoids present in crude hydroethanolic extract (CHE) and fractions obtained from B. holophylla leaves against ZIKV. O-glycosylated flavonoids were characterized by high-performance liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS/MS). The cytotoxic concentration and the effective concentration for 50% of the cells (CC₅₀ and EC₅₀, respectively) were determined, and the selectivity index (SI) was calculated. Molecular networks were constructed based on the chemical composition of the samples and global antiviral activity data using the Global Natural Products Social Molecular Networking (GNPS) platform. Protein–ligand docking was performed in the NS2B-NS3 protease, NS3 helicase, and NS5 methyltransferase of the ZIKV. CHE showed greater antiviral activity at a multiplicity of infection (MOI) of 1.0, with an EC₅₀ of 11.93 µg/mL, SI = 13.38, and reduced cytopathic effects. Molecular networks indicated that O-glycosylated flavonoids are responsible for the activity against ZIKV, being quercetin-O-deoxyhexoside more selective and effective. Molecular docking confirmed the inhibitory activity of quercetin-O-deoxyhexoside, which showed an affinity for the tested targets, especially for NS2B-NS3 protease. The results showed that B. holophylla has flavonoids with potential for future therapeutic applications against ZIKV. Full article

Anthurium is the second largest tropical flower crop in the world. The international market has urgent demand for anthurium varieties with different spathe colors, which mainly arises from the types and contents of anthocyanin. The flavonoid 3-O-glycosyltransferase (UF3GT) gene is the key enzyme involved in promoting anthocyanin accumulation through glycosylation downstream of the anthocyanin synthesis pathway (ASP). Abnormal functioning of UFGT usually results in a reduction in or loss of anthocyanins. The aim of this study was to reveal the role of one anthurium UFGT gene (AnUFGT1) in ‘Xueyu’ (X), an anthocyanin-deficient mutant of ‘Alabama’. Metabolome analysis was used to analyze the metabolic products in the ASP to determine the possible key link of the anthocyanin deletion mutation. Agrobacterium-mediated transformation of Arabidopsis UFGT functionally deficient mutant (ufgt) and ‘X’ validated the function of AnUFGT1. The results of comparative metabolome analysis of ‘X’ and ‘Alabama’ showed that there was no significant difference in product levels upstream of ASP. The expression levels of AnUFGT1 were significantly greater in ‘Alabama’ than in ‘X’. The overexpression of AnUFGT1 in ufgt significantly increased its anthocyanin contents. The overexpression of AnUFGT1 in ‘X’, mediated by a new injection method, can only promote the synthesis of trace anthocyanins. These results showed that AnUFGT1 could fully compensate the phenotype of ufgt, but only partially compensate the anthocyanidin-deficient phenotype of anthurium mutant X. This difference suggested that anthocyanin-deletion mutations in anthurium ‘X’ are associated with AnUFGT1, but AnUFGT1 is not the only factor. There should be other factors interacting with AnUFGT1 that cause anthocyanin deficiency. Full article

Hedera helix is a traditional medicinal plant. Its primary active ingredients are oleanane-type saponins, which have extensive pharmacological effects such as gastric mucosal protection, autophagy regulation actions, and antiviral properties. However, the glycosylation-modifying enzymes responsible for catalyzing oleanane-type saponin biosynthesis remain unidentified. Through transcriptome, cluster analysis, and PSPG structural domain, this study preliminarily screened four candidate UDP-glycosyltransferases (UGTs), including Unigene26859, Unigene31717, CL11391.Contig2, and CL144.Contig9. In in vitro enzymatic reactions, it has been observed that Unigene26859 (HhUGT74AG11) has the ability to facilitate the conversion of oleanolic acid, resulting in the production of oleanolic acid 28-O-glucopyranosyl ester. Moreover, HhUGT74AG11 exhibits extensive substrate hybridity and specific stereoselectivity and can transfer glycosyl donors to the C-28 site of various oleanane-type triterpenoids (hederagenin and calenduloside E) and the C-7 site of flavonoids (tectorigenin). Cluster analysis found that HhUGT74AG11 is clustered together with functionally identified genes AeUGT74AG6, CaUGT74AG2, and PgUGT74AE2, further verifying the possible reason for HhUGT74AG11 catalyzing substrate generalization. In this study, a novel glycosyltransferase, HhUGT74AG11, was characterized that plays a role in oleanane-type saponins biosynthesis in H. helix, providing a theoretical basis for the production of rare and valuable triterpenoid saponins. Full article

Atraphaxis pyrifolia is a native species of Central Asia, known for curing several disorders. The species has little knowledges about its chemical composition and any information about its morphological characteristics despite its importance in traditional Asian medicine. This is one of the first approaches to the phytochemical and morphological characterization of this species. Micro-morphology was performed on the stem, and leaf parts of this plant to profile the morpho-anatomical characters using brightfield, fluorescence, polarized and scanning electron microscopy. Leaves were extracted with hexane and methanol. The hexane extract was analyzed using GC-MS analysis revealing the major presence of γ-sitosterol and nonacosane. The methanolic extract was submitted to Vacuum Liquid Chromatography and Sephadex LH-20. HPTLC, HR-ESI-MS and NMR techniques were used to identify the main compounds. Four glycosylated flavonoids were isolated: 8-O-acetyl-7-O-methyl-3-O-α-l-rhamnopyranosylgossypetin (Compound 1), and 7-O-methyl-3-O-α-l-rhamnopyranosylgossypetin (Compound 3), and two other compounds reported for the first time in the literature (Compounds 2 and 4). The findings presented herein furnish pertinent information essential for the identification and authentication of this medicinal plant. Such insights are invaluable for facilitating robust quality control measures and serve as a foundational framework for subsequent endeavours in metabolic, pharmacological, and taxonomical analyses. Full article

Safflower (Carthamus tinctorius L.) has been recognized for its medicinal value, but there have been limited studies on the glycosyltransferases involved in the biosynthesis of flavonoid glycosides from safflower. In this research, we identified two highly efficient flavonoid O-glycosyltransferases, CtOGT1 and CtOGT2, from safflower performing local BLAST alignment. By constructing a prokaryotic expression vector, we conducted in vitro enzymatic reactions and discovered that these enzymes were capable of catalyzing two-step O-glycosylation using substrates such as kaempferol, quercetin, and eriodictyol. Moreover, they exhibited efficient catalytic activity towards various compounds, including flavones (apigenin, scutellarein), dihydrochalcone (phloretin), isoflavones (genistein, daidzein), flavanones (naringenin, glycyrrhizin), and flavanonols (dihydrokaempferol), leading to the formation of O-glycosides. The broad substrate specificity of these enzymes is noteworthy. This study provides valuable insights into the biosynthetic pathways of flavonoid glycosides in safflower. The discovery of CtOGT1 and CtOGT2 enhances our understanding of the enzymatic processes involved in synthesizing flavonoid glycosides in safflower, contributing to the overall comprehension of secondary metabolite biosynthesis in this plant species. Full article