Search Results (232)

Phytoalexins are antimicrobial compounds of diverse chemical classes whose production is triggered in plants in response to pathogen infection. This study demonstrated that spraying with a celery flavonoid-rich extract (CFRE) or a spinach flavonoid-rich extract (SFRE) enhanced the production of phytoalexins in cucumber leaves artificially infected with powdery mildew incited by Podosphaera fusca. High-performance liquid chromatographic (HPLC) analysis revealed a noticeable increase in the content of phenolic acids, including caffeic acid, ellagic acid, ferulic acid, gallic acid, p-coumaric acid, and syringic acid, as well as the flavonoid rutin in both non-inoculated and inoculated leaves of cucumber seedlings treated with CFRE and SFRE, compared to healthy untreated leaves used as a control. Fluorescence microscopy revealed the accumulation of phenolic acid compounds in chloroplasts and at the periphery of epidermal cells. Overall, results suggest the reduced severity of P. fusca infection following the application of CFRE and SFRE in cucumber leaves could be due, at least in part, to the production of phytoalexins of polyphenolic nature. These findings provide insights into the mechanisms of systemic resistance induced by CFRE and SFRE. Moreover, they confirm these two natural flavonoid-rich products could be promising alternatives to synthetic chemical fungicides for the safe and ecofriendly control of cucumber powdery mildew. Full article

Background/Objectives: Understanding the molecular interactions between small bioactive compounds and serum albumins is essential for drug development and pharmacokinetics. Noraucuparin, a biphenyl-type phytoalexin with promising pharmacological properties, has shown a strong binding affinity to bovine serum albumin (BSA), a model protein for drug transport. This study aims to elucidate the structural and energetic characteristics of the noraucuparin–BSA complex under physiological and slightly elevated temperatures. Methods: Microsecond-scale molecular dynamics (MD) simulations and Molecular Mechanics Generalized Born Surface Area (MMGBSA)-binding-free energy calculations were performed to investigate the interaction between noraucuparin and BSA at 298 K and 310 K. Conformational flexibility and per-residue energy decomposition analyses were conducted, along with interaction network mapping to assess ligand-induced rearrangements. Results: Noraucuparin preferentially binds to site II of BSA, near the ibuprofen-binding pocket, with stabilization driven by hydrogen bonding and hydrophobic interactions. Binding at 298 K notably increased the structural mobility of BSA, affecting its global conformational dynamics. Key residues, such as Trp213, Arg217, and Leu237, contributed significantly to complex stability, and the ligand induced localized rearrangements in the protein’s intramolecular interaction network. Conclusions: These findings offer insights into the dynamic behavior of the noraucuparin–BSA complex and enhance the understanding of serum albumin–ligand interactions, with potential implications for drug delivery systems. Full article

Wheat (Triticum aestivum L.) is the world’s most indispensable staple crop and a vital source of food for human diet. Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), constitutes a severe threat to wheat production and in severe cases, the crop fails completely. Anmai1350 (AM1350) is moderately resistant to leaf rust and powdery mildew, and highly susceptible to sheath blight and fusarium head blight. We found that the length and area of mycelium in AM1350 cells varied at different time points of Pst infection. To investigate the molecular mechanism of AM1350 resistance to Pst, we performed transcriptome sequencing (RNA-seq). In this study, we analyzed the transcriptomic changes of the seedling leaves of AM1350 at different stages of Pst infection at 0 h post-infection (hpi), 6 hpi, 24 hpi, 48 hpi, 72 hpi, and 120 hpi through RNA-seq. Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) was used to validate RNA-seq data. It was determined that there were differences in the differentially expressed genes (DEGs) of AM1350, and the upregulation and downregulation of the DEGs changed with the time of infection. At different time points, there were varying degrees of enrichment in the response pathways of AM1350, such as the ”MAPK signaling pathway–plant”, the “plant–pathogen interaction” pathway and other pathways. After Pst infected AM1350, the reactive oxygen species (ROS) content gradually increases. The ROS is toxic to Pst, promotes the synthesis of phytoalexins, and inhibits the spread of Pst. As a result, AM1350 shows resistance to Pst race CYR34. The main objective of this study is to provide a better understanding for resistance mechanisms of wheat in response to Pst infections and to avoid production loss. Full article

Resveratrol is a naturally occurring phytoalexin found in red grapes, cocoa berries, and red grape wine. This compound exhibits potent antioxidant, anti-inflammatory, and anticancer properties. However, its clinical application is significantly hindered by poor aqueous solubility and rapid degradation at physiological pH, resulting in extremely low systemic bioavailability. This review explores three key aspects: green extraction methods for the efficient and sustainable isolation of resveratrol; structure–activity relationship studies of resveratrol derivatives to identify compounds with improved bioavailability and therapeutic efficacy; and advanced drug delivery systems to enhance resveratrol solubility, stability, and achieve targeted tissue delivery. All of these solutions collectively aim to increase resveratrol bioavailability, enabling the development of effective pharmaceutical formulations and maximizing the clinical potential of this promising compound. The aim of this review is to summarize the key studies published in the last five years, highlighting innovative advancements in sustainable extraction, structural modifications, and delivery strategies for resveratrol. Full article

The crucial roles of the lipase-like protein enhanced disease susceptibility 1 (EDS1) and phytoalexin deficient 4 (PAD4) in disease resistance in Arabidopsis have been identified. However, their function in rice (Oryza sativa L.) resistance to brown planthopper (BPH, Nilaparvata lugens Stål), the most notorious pest of rice, remains unknown. In this study, the transcript levels of OsEDS1 and OsPAD4 were rapidly altered by BPH infestation. Mutation in either OsPAD4 or OsEDS1 resulted in increased rice susceptibility to BPH, which was associated with increased honeydew excretion and an increased host preference of BPH. Furthermore, mutation in either OsPAD4 or OsEDS1 led to decreased basal levels of salicylic acid (SA) and jasmonic acid (JA) in the absence of BPH, along with the depressed expression of the defense-responsive genes OsPAL, OsICS1, OsPR1a, OsLOX1, OsAOS1 and OsJAZ11 involved in SA and JA biosynthesis and signaling. The BPH infestation-mediated elevation of SA levels and the expression of SA biosynthesis and signaling genes was dampened in eds1 and pad4 plants, whereas BPH infestation-mediated depressions of JA levels and the expression of JA biosynthesis and signaling genes were reversed in eds1 and pad4 plants. Taken together, our findings indicated that both OsPAD4 and OsEDS1 positively regulate rice resistance to BPH. Full article

Methoxycamalexins are close structural derivatives of the indolic phytoalexin Camalexin, which is a well-known drug lead with an antiproliferative and antioxidant profile. 6-methoxycamalexin, 7-methoxycamalexin, and 6,7-dimethoxycamalexin are natural bioactive products, and there is significant interest in the development of efficient methods for the synthesis of structurally related analogues. Herein, we describe an efficient and high-yielding method for the synthesis of variously substituted hydroxy-, bezyloxy, and methoxycamalexins. A set of methoxy-, hydroxy-, and benzyloxy-indoles were successfully amidoalkylated with N-acyliminium reagents derived in situ from the reaction of thiazole or methylthiazoles with Troc chloride. Eleven novel N-acylated analogues were synthesized, with yields ranging from 77% to 98%. Subsequent oxidative reactions with o-chloranil or DDQ led to 10 novel oxy-camalexins in 62–98% yield. This two-step approach allowed the synthesis of two 4,6-dimethoxy camalexins, which are difficult to obtain using published methods. The structure of the obtained products was unequivocally determined by ¹H-, ¹³C{¹H}-, HSQC-NMR, FTIR, and HRMS spectral analyses. An in silico assay was carried out on the obtained products to assess their general toxicity and physicochemical properties, including their compliance with Lipinski’s rule of five. The results indicate that all compounds have good potential to be developed as drugs or agrochemicals. Full article

Phytoalexins are specialized metabolites that are synthesized by plants in response to pathogens. A paradigm in transcription factor (TF) biology is that conserved TFs have dedicated roles across plant lineages in regulating specific branches of specialized metabolism. However, the Arabidopsis (Arabidopsis thaliana) NAC family TF ANAC042 (a.k.a. JUNGBRUNNEN1 or JUB1) regulates the synthesis of camalexin, a Trp-derived phytoalexin specifically produced by several Brassicaceae species, whereas its homolog in soybean (Glycine max) regulates the synthesis of glyceollins, which are Phe-derived phytoalexins specific to soybean. The question addressed by this research is whether ANAC042 broadly regulates phytoalexin biosynthetic pathways in Arabidopsis. Using a novel matrix-assisted laser desorption ionization high-resolution mass spectrometry (MALDI-HRMS) method, we found that the Arabidopsis loss-of-function mutant anac042–1 elicited with bacterial flagellin (Flg22) is deficient in lineage-specific Trp- and conserved Phe-derived phytoalexins—namely camalexin and 4-hydroxyindole-3-carbonyl nitrile (4OH-ICN), and pathogen-inducible monolignols and scopoletin, respectively. Overexpressing ANAC042 in the anac042-1 mutant restored or exceeded wildtype amounts of the metabolites. The expression of phytoalexin biosynthetic genes in mutant and overexpression lines mirrored the accumulation of metabolites. Yeast-one hybrid and promoter-reporter assays in Nicotiana benthamiana found that the ANAC042 protein directly binds and activates the promoters of CYP71B15, CYP71A12, and PAL1 genes for the synthesis of camalexin, 4OH-ICN, and pathogen-inducible monolignol/scopoletin, respectively. Our results demonstrate that ANAC042 regulates conserved and lineage-specific phytoalexin pathways in Arabidopsis. The latter suggests that it is an opportunistic TF that has coopted lineage-specific genes into phytoalexin metabolism, thus providing an exception to the current paradigm. Full article

Resveratrol is the most important biopotential phytoalexin of the stilbene group (natural polyphenolic secondary metabolites), synthesized naturally by the action of biotic and abiotic factors on the plant. The yield of individual bioactive compounds isolated from grapevine components, products and by-products is directly dependent on the conditions of the synthesis, extraction and identification techniques used. Modern methods of synthesis and extraction, as well as identification techniques, are centred on the use of non-toxic solvents that have the advantages of the realisation of rapid extractions, maintenance of optimal parameters, and low energy consumption; this is a challenge with promising results for various industrial applications. Actionable advances in identifying and analysing stilbenes consist of techniques for coupling synthesis/extraction/identification methods that have proven accurate, reproducible and efficient. The main challenge remains to keep resveratrol compositionally unaltered while increasing its microbiome solubility and stability as a nutraceutical in the food industry. Full article

Plant-based stilbenes are low-molecular-weight polyphenolic compounds that exhibit anti-oxidant, anti-microbial, anti-fungal, anti-inflammatory, anti-diabetic, cardioprotective, neuroprotective, and anti-cancer activities. They are phytoalexins produced in diverse plant species in response to stress, such as fungal and bacterial infections or excessive UV irradiation. Plant-derived dietary products containing stilbenes are common components of the human diet. Stilbenes appear to be promising chemopreventive and chemotherapeutic agents. Accumulating evidence indicates that stilbenes are able to trigger both apoptotic and autophagic molecular pathways in many human cancer cell lines. Of note, the molecular crosstalk between autophagy and apoptosis under cellular stress conditions determines the cell fate. The autophagy and apoptosis relationship is complex and depends on the cellular context, e.g., cell type and cellular stress level. Apoptosis is a type of regulated cell death, whereas autophagy may act as a pro-survival or pro-death mechanism depending on the context. The interplay between autophagy and apoptosis may have an important impact on chemotherapy efficiency. This review focuses on the in vitro effects of stilbenes in different human cancer cell lines concerning the interplay between autophagy and apoptosis. Full article

Corn (Zea mays L.) productivity is often compromised by phytosanitary challenges, with fungal disease like Curvularia leaf spot being particularly significant. While synthetic fungicides are commonly used, there is growing interest in exploring alternative compounds that are effective against pathogens, ensure food safety, and have low toxicity to non-target organisms. In this study, we examined the biochemical changes in corn plants treated with Lippia sidoides essential oil and its major compound, thymol. Both treatments serve as preventive measures for inoculated plants and induced resistance. We tested five concentrations of each product in in vivo experiments. After evaluating the area under the disease progress curve, we analyzed leaf samples for enzymatic activities, including superoxide dismutase, catalase, ascorbate peroxidase, and chitinase. Phytoalexin induction was assessed using soybean cotyledons and sorghum mesocotyls. Cytotoxicity tests revealed lower toxicity at concentrations below 50 µL/mL. Both essential oil and thymol stimulated the production of reactive oxygen species, with thymol primarily activating catalase and L. sidoides oil increasing ascorbate peroxidase levels. Both thymol and L. sidoides were also key activators of chitinase. These findings suggest that L. sidoides essential oil and thymol are promising candidates for developing biological control products to enhance plant defense against pathogens. Full article

Resveratrol, a bioactive phytoalexin, has been extensively studied as a pharmaceutical and nutraceutical candidate for the treatment of various diseases. Although its therapeutic effects have been largely attributed to its anti-oxidant properties, its underlying mechanisms and dose dependency are not well understood. Recent studies have shown that cell-free chromatin particles (cfChPs), which are released daily from billions of dying cells, can enter circulation and be internalized by healthy cells, wherein they trigger various damaging effects, including double-strand DNA breaks. Notably, deactivating cfChPs using a mixture of resveratrol and copper can neutralize their harmful effects. The addition of copper imparts a novel therapeutic property to resveratrol viz. the generation of reactive oxygen species (ROS), which are capable of deactivating cfChPs without damaging the genomic DNA. This perspective article discusses how the deactivation of cfChPs via the ROS generated by combining resveratrol with copper can have multiple therapeutic effects. Exploiting the damaging effects of ROS to deactivate cfChPs and ameliorate disease conditions may be a viable therapeutic approach. Full article

Colorectal cancer is one of the most common cancers worldwide and has a high mortality rate. In this study, we investigated the cytotoxic, proapoptotic, and anti-invasive effects of the synthetic indole phytoalexin MB-653. The antiproliferative effect was determined using an MTT assay, showing IC₅₀ values of 5.8 ± 0.3 μmol/L for HCT116 cells and 6.1 ± 2.1 μmol/L for Caco2 cells. Flow cytometry and Western blot analysis were employed to investigate the molecular mechanisms underlying cytotoxicity, proapoptotic action, and anti-invasion effects. The proapoptotic activity was evidenced by the activation of caspases 3 and 7, mitochondrial dysfunction, and an increased number of apoptotic cells, confirmed by annexin V/PI and AO/PI staining. Additionally, MB-653 induces dose-dependent G2/M phase cell cycle arrest, the cause of which could be cyclin B1/CDC2 complex dysfunction and/or a decrease in α-tubulin protein expression. Another important observation was that MB-653 modulated several signalling pathways associated with various cellular activities, including survival, proliferation, tumour invasiveness, metastasis, and epithelial–mesenchymal transition (EMT). We further demonstrated its safety for topical and parenteral application. To sum up, our results indicate the real potential of MB-653 in treating colorectal cancer. Full article

The synthesis of indole phytoalexin-like analogs related to alkyl (((1-(4-substitutedphenyl)-3-oxo-3-phenylpropyl)thio)carbonothioyl)-ʟ-tryptophanate 1a–d and the evaluation of their antifungal activity against the phytopathogen Fusarium oxysporum is reported. The target compounds were synthesized in the following two stages: (1) the initial esterification of ʟ-tryptophan, which reacted with trimethyl silane chloride and simple aliphatic alcohols (R = Me, Et) under microwave irradiation (MWI) at 100 °C to obtain the respective alkyl ester 2a–b; (2) the resulting mixture of ʟ-tryptophanates 2a–b with carbon disulfide and (E)-chalcone 3a–b under MWI at 50 °C during 60 min, followed by purification through classical column chromatography (55–76% yields). The products were obtained as mixtures of (S,R) and (S,S) diastereoisomers. An LC-DAD-MS analysis allowed us to establish the ratio of these diastereoisomers, and subsequent DFT/B3LYP-based computational calculations of the NMR ¹H chemical shifts suggested that the major diastereoisomer involved an (S,R) absolute configuration, comprising more than 60% of the mixture. The compounds 1a–d were subjected to an antifungal activity test against the phytopathogen F. oxysporum using an amended medium-based assay. Compound series 1 showed inhibition percentages of 80% at the first concentration and IC₅₀ values between 0.33 and 5.71 mM, demonstrating greater potential as antifungal agents compared to other ʟ-tryptophan derivatives like alkyl (2S)-3-(1H-indol-3-yl)-2-{[(1Z)-3-oxobut-1-en-1-yl]amino}propanoate, which presented lower inhibition percentages. In summary, phytoalexin analogs derived from ʟ-tryptophan and (E)-chalcones significantly inhibited the mycelial growth of Fusarium oxysporum, indicating their potential as effective antifungal agents. Full article

Rice (Oryza sativa) produces phenolamides and diterpenoids as major phytoalexins. Although the biosynthetic pathways of phenolamides and diterpenoids in plants have been revealed, knowledge of their accumulation regulatory mechanisms remains limited, and, in particular, no co-regulatory factor has been identified to date. Here, using a combined co-expression and evolutionary analysis, we identified the basic helix–loop–helix (bHLH) transcription factor OsbHLH5 as a positive bifunctional regulator of phenolamide and diterpenoid biosynthesis in rice. Metabolomic analysis revealed that OsbHLH5 significantly increased the content of phenolamides (such as feruloyl tryptamine (Fer-Trm) and p-coumaroyl tyramine (Cou-Tyr)) and diterpenoid phytoalexins (such as momilactones A, momilactones B) in the overexpression lines, while their content was reduced in the OsbHLH5 knockout lines. Gene expression and dual-luciferase assays revealed that OsbHLH5 activates phenolamide biosynthetic genes (including putrescine hydroxycinnamoyltransferase 3 (OsPHT3), tyramine hydroxycinnamoyltransferases 1/2 (OsTHT1/2), and tryptamine benzoyltransferase 2 (OsTBT2)) as well as diterpenoid biosynthetic genes (including copalyl diphosphate synthase 4 (OsCPS4) and kaurene synthase-like 4/7/10/11 (OsKSL4/7/10/11)). Furthermore, we have demonstrated that OsbHLH5 is induced by jasmonic acid (JA), while pathogen inoculation assays indicated that the overexpression of OsbHLH5 in transgenic rice plants leads to enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo). Overall, we have identified a positive regulator of phenolamide and diterpenoid biosynthesis and have demonstrated that biotic stress induces phytoalexin accumulation partly in an OsbHLH5-dependent manner, providing new insights into the metabolic interactions involved in pathogen response and offering valuable gene resources for the development, through genetic improvement, of new rice varieties that are resistant to diseases. Full article

Legumes are a rich source of polyphenolic compounds known for their ability to promote health. Under stress conditions, legumes have been shown to produce higher levels of secondary metabolites, as a defensive mechanism. Hence, the present study aimed to induce legume seeds (e.g., soybean, chickpea, green pea, and red kidney bean) by inoculating them with Aspergillus sojae (A. sojae) and to evaluate the extracts for phytoalexins, phenolics, and antioxidant, antiobesity, and antidiabetic potentials. The UPLC-DAD findings of A. sojae-induced legumes showed medicarpin and maackiain in chickpea, pisatin in green pea, glyceollin I-III in soybean, and kievitone and phaseollin in red kidney bean. All induced legumes exhibited a higher total polyphenol content compared to the non-induced ones. Among induced legumes, soybean exhibited a higher (4.85 mg GAE/g) polyphenol content. The UPLC-ESI-QTOF-MS/MS findings established that legumes contained substantial levels of protocatechuic acid, vanillic acid, ferulic acid, chlorogenic acid, coumaric acid, 4-hydroxybenzoic acid, and caffeic acid. The results of antioxidant assays revealed a significantly higher level of activity in induced red kidney bean and soybean, whereas the level of activity in non-induced legumes was markedly lower. Moreover, induced red kidney bean effectively inhibited α-glucosidase (87.2%) and α-amylase (63.90%) at 5 mg/mL. Additionally, the maximum lipase inhibitory effects were displayed by induced soybean (72.54%) at 20 mg/mL. Full article