The control of oxidative stress with natural active substances could limit the development of numerous pathologies. Our objective was to study the antiradical effects of resveratrol (RSV), ε-viniferin (VNF) and vitisin B (VB) alone or in a combination, and those of a stilbene-enriched ex-tract (fraction). In the DPPH, FRAP, and NO scavenging assays, RSV present the highest activity with an IC50 of 83.69, 15.38 and 229 µM, respectively. Binary combinations resulted in additive interaction in the DPPH assay, synergic interaction for RSV+VNF and antagonistic for the others in the FRAP assay, and additive interaction for RSV+VNF or RSV+VB and antagonistic for VNF+VB in the NO scavenging assay. There was no significant difference between the antioxi-dant activity of the fraction and the combination RSV+VNF. In conclusion, RSV presented the highest effects, followed by VNF and VB. Interactions revealed additive or synergistic effects, depending on the combination of stilbenes and the assay.

In the Valpolicella area (Verona - Italy) Vitis vinifera cv. Corvina is the main grape variety used to produce Amarone wine. Before starting the winemaking process, the Corvina grapes are stored in a withering (i.e., dehydrating) warehouse until about 30% of the berry weight is lost (WL). This practice is followed to have the chemical metabolites concentrate in the berry and enrich the Amarone wine in aroma and antioxidant compounds. In compliance with the guidelines and strict Amarone protocol set by the Consorzio of Amarone-Valpolicella, withering must be carried out by setting the grapes in a suitable environment, either under controlled relative air humidity (RH) conditions and wind speed (WS) – no temperature modification is to be applied – or, following the traditional methods, in open-air natural environmental conditions. In general, the two processes have different dehydration kinetics due to the different conditions in terms of temperature, RH, and WS, which affect the accumulation of sugars and organic acids and the biosynthesis of sec-ondary metabolites such as stilbenes and glycoside aroma precursors. For this study, the two grape-withering processes were carried out under controlled (C) and not-controlled (NC) condi-tions and the final compositions of the Corvina dried grapes were compared also to evaluate the effects on the organoleptic characteristics of Amarone wine. The findings highlighted differences between the two processes mainly in terms of the secondary metabolites of the dried grapes, which affect the organoleptic characteristics of Amarone wine.

Phytoalexins are naturally-occurring molecules with antimicrobial activity deriving from the secondary metabolism of plants, which are synthesized in response to physical agents or stresses, phytopathogenic agents (fungi, bacteria and viruses) as well as numerous chemical compounds and biological control agents. Among these, grapevine phytoalexins, which belong to the chem-ical group of stilbenes, exhibit biocidal activity against a large number and a variety of plant pathogens. An important issue in research on these compounds is to be able to stimulate their synthesis in planta and to determine whether the induction of their production can serve as a basis for protecting that plant against its pathogens. Quite a few chemical compounds, derivatives of phytohormones bio-elicitors as well as biocontrol agents have been used to induce the synthesis of stilbene phytoalexins with the aim of conferring protection to grapevine against its main dis-eases (gray mold, downy mildew, powdery mildew and esca). This article reviews the experi-ments that have been carried out in this direction during the last thirty years and shows that the observed protective effects towards pathogens are generally linked to induction and priming of the grapevine phytoalexin response, confirming the interest of using, in a more general way, stimulation of the production of phytoalexins in plants as a basis for crop protection.

Secondary phenolic metabolites are defined as valuable natural products synthesized by different organisms that are not essential for growth and development. These compounds play an essential role in plant defense mechanisms, and an important role in the pharmaceutical, cosmetics, food, and agricultural industries. Despite the vast chemical diversity of natural compounds, their content in plants is very low, in consequence, it eliminates the possibility of the production of these interesting secondary metabolites from plants. Therefore, microorganisms are widely used as cell factories by industrial biotechnology to the production of different non-native compounds. Among microorganisms commonly used in biotechnological applications, yeasts are prominent host for the diverse secondary metabolite biosynthetic pathways. Saccharomyces cerevisiae is often regarded as the better host organism for the heterologous production of phenolics compounds, especially if the expression of different plant genes is necessary.

Enteric septicemia of catfish, columnaris disease, and streptococcosis, caused by Edwardsiella ictaluri, Flavobacterium columnare, and Streptococcus iniae, respectively, are the most common bacterial diseases of economic significance for the pond-raised channel catfish Ictalurus punctatus industry. Several management practices are used by catfish farmers to prevent large financial losses from these diseases such as the use of commercial antibiotics and other chemicals. In order to discover environmentally benign alternatives, using a rapid bioassay, we evaluated a crude extract from the roots of muscadine Vitis rotundifolia against these fish pathogenic bacteria and determined that the extract was most active against F. columnare. Subsequently, several isolated compounds from the root extract were further evaluated against F. columnare. Among these isolated compounds, (+)-hopeaphenol (2) and (+)-vitisin A (3) were found to be the most active against F. columnare, with 24-h 50% inhibition concentrations of 4.0±0.7 and 7.7±0.6 mg/L, respectively, and minimum inhibitory concentrations of 9.1±0 mg/L for each compound. Efficacy testing of 2 and 3 is necessary to further evaluate the potential for these compounds to be used as antibacterial agents for managing columnaris disease.

Decoctions, macerations and fumigations of the stem bark and wood of Terminalia brownii Fresen. are used in traditional medicine for fungal infections and as pesticides on field crops and in traditional granaries in Sudan. In addition, T. brownii is commonly used for protecting wooden houses and furniture. Therefore, using agar disc diffusion and macrodilution methods, eight extracts of various polarities from the stem wood and bark were screened for their growth inhibitory effects against filamentous fungi commonly causing fruit, vegetable and grain decay, as well as infections in the immunocompromised host. Ethyl acetate extracts of the stem wood and bark gave the best antifungal activities, with MIC values of 250 µg/ml against Nattrassia mangiferae and Fusarium verticillioides, and 500 µg/ml against Aspergillus niger and Aspergillus flavus. Aqueous extracts gave almost as potent effects as the ethyl acetate extracts against the Aspergillus and Fusarium strains, and were slightly more active than the ethyl acetate extracts against Nattrassia mangiferae. Thin layer chromatography, RP-HPLC-DAD and tandem mass spectrometry (LC-MS/MS), were employed to identify the chemical constituents in the ethyl acetate fractions of the stem bark and wood. The stem bark and wood were found to have a similar qualitative composition of polyphenols and triterpenoids, but differed quantitatively from each other. The stilbene derivatives, cis- (3) and trans- (4) resveratrol-3-O-β-galloylglucoside, were identified for the first time in T. brownii. Moreover, methyl-(S)-flavogallonate (5), quercetin-7-β-O-di-glucoside (8), quercetin-7-O-galloyl-glucoside (10), naringenin-4`-methoxy-7-pyranoside (7), 5,6-dihydroxy-3`,4`,7-tri-methoxy flavone (12), gallagic acid dilactone (terminalin) (6), a corilagin derivative (9) and two oleanane type triterpenoids (1) and (2) were characterized. Our results justify the traditional uses of macerations and decoctions of T. brownii stem wood and bark for crop and wood protection and demonstrate that standardized extracts could have uses for the eco-friendly control of plant pathogenic fungi in African agroforestry systems. Likewise, our results justify the traditional uses of these preparations for the treatment of skin infections caused by filamentous fungi.