Interrelationships of the structures and antioxidant activities of some flavonoids from the plants of Central Asia

Mixtures of Macro and Micronutrients Control Grape Powdery Mildew and Alter Berry Metabolites

Powdery mildew caused by the fungus Erysiphe necator is a major grape disease worldwide. It attacks foliage and berries and reduces yield and wine quality. Fungicides are mainly used for combating the disease. Fungicide resistance and the global requisite to reduce pesticide deployment encourage the use of environment-friendly alternatives for disease management. Our field experiments showed that the foliar application of the potassium phosphate fertilizer Top-KP+ (1-50-33 NPK) reduced disease incidence on leaves and clusters by 15-65% and severity by 75-90%, compared to untreated vines. Top-KP+ mixed with Nanovatz (containing the micronutrients boron (B) and zinc (Zn)) or with TruPhos Platinum (a mixture containing N, P₂O₅, K₂O, Zn, B, Mg, Fe, Mn, Cu, Mo, and CO) further reduced disease incidence by 30-90% and disease severity by 85-95%. These fertilizers were as effective as the fungicide tebuconazole. Tank mixtures of fertilizers and tebuconazole further enhanced control efficacy in the vineyards. The modes of action of fertilizers in disease control were elucidated via tests with grape seedlings, microscopy, and berry metabolomics. Fertilizers applied preventively to the foliage of grape seedlings inhibited powdery mildew development. Application onto existing mildew colonies plasmolyzed mycelia and conidia and arrested the development of the disease. Berries treated with fertilizers or with a fungicide showed a significant increase in anti-fungal and antioxidant metabolites. Twenty-two metabolites, including non-protein amino acids and carbohydrates, known for their anti-fungal and bioactive effects, were significantly upregulated in grapes treated with fertilizers as compared to grapes treated with a fungicide, suggesting possible indirect activity against the pathogen. Esters and organic acids that contribute to wine quality were also upregulated. We conclude that integrating macro and micronutrients in spray programs in commercial vineyards shall control powdery mildew, reduce fungicide deployment, delay the buildup of fungicide resistance, and may improve wine quality.

Effect of plant flavonoids on the volume regulation of rat thymocytes under hypoosmotic stress

BACKGROUND

Cell volume regulation and volume-regulated anion channels are critical for cell survival in non-isosmotic conditions, and dysregulation of this system is detrimental. Although genes and proteins underlying this basic cellular machinery were recently identified, the pharmacology remains poorly explored.

METHODS

We examined effects of 16 flavonoids on the regulatory volume decrease (RVD) of thymocytes under hypoosmotic stress assessed by light transmittance and on the activity of volume-sensitive chloride channel by patch-clamp technique.

RESULTS

Comparison of effects of flavonoids on RVD revealed a group of four active substances with lehmannin being the strongest inhibitor (IC50 = 8.8 μM). Structure-functional comparison suggested that hydrophobicity brought about by methoxy, prenyl or lavandulyl groups as well as by the absence of glucosyl fragment together with localization of the phenyl ring B at the position C2 (which is at C3 in totally inactive isoflavones) are important structural determinants for the flavonoids activity as volume regulation inhibitors. All active flavonoids suppressed RVD under Gramicidin D-NMDG hypotonic stress conditions when cationic permeability was increased by an ionophore, gramicidin D, with all extracellular monovalent cations replaced with bulky NMDG+ suggesting that they target volume-sensitive anionic permeability. While effects of hispidulin and pulicarin were only partial, lehmannin and pinocembrin completely abolished RVD under Gramicidin D-NMDG conditions. In direct patch-clamp experiments, lehmannin and pinocembrin produced a strong inhibiting effect on the swelling-induced whole-cell chloride conductance in a voltage-independent manner.

CONCLUSION

Lehmannin, pinocembrin, and possibly hispidulin and pulicarin may serve as leads for developing effective low-toxic immunomodulators.

Evaluation of biological activity of crude extracts from plants used in Yucatecan traditional medicine part I. Antioxidant, antimicrobial and beta-glucosidase inhibition activities

Bioactivity of extracts from leaves, stems and roots of twelve plants commonly used in Yucatecan traditional medicine were evaluated in four bioassays. Crude extracts from ten plants showed significant activity in the inhibition of bleaching of beta-carotene assay, while thirteen extracts showed activity in the reduction of 2, 2- diphenyl-1-picrylhydrazyl radical (DPPH) assay. In the antimicrobial bioassay, the major activity was presented by the root extract of Jatropha gaumeri and in the beta-glucosidase inhibition activity assay the strongest activity was observed in the stem and root extracts of Solanum hirtum.