Ivana Generalić

Phenolic Profile, Antioxidant Capacity, and Antimicrobial Activity of Leaf Extracts from Six Vitis vinifera L. Varieties

The phenolic composition, antioxidant activity, and antimicrobial activity of extracts from vine leaves of six grape varieties collected in May, August, and September was studied. The phenolic potential of the extracts was dependent on variety and picking-time. Extracts of leaves collected in September were the richest in total phenols, flavonoids, flavonols, and stilbenes. The antioxidant properties determined by ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl assays, and antimicrobial activity against Stapylococcus aureus, Bacillus cereus, Campylobacter jejuni, Escherichia coli, and Salmonella Infantis were good and in correlation with the chemical composition changes of the leaf extracts. The results indicated that leaves remaining on the vine in September after the grape harvest could be especially promising as an inexpensive source of effective antioxidant/antimicrobial agents.

Seasonal Variations of Phenolic Compounds and Biological Properties in Sage (Salvia officinalis L.)

The aim was to investigate the phenolic content, antioxidant capacity, and antibacterial activity of Dalmatian sage (Salvia officinalis L.) leaves collected during different vegetation periods. Separation and quantification of the individual phenols were performed by reversed‐phase (RP)‐HPLC coupled with a PDA (photodiode array) detector and using an internal standard, while the contents of total phenols, flavonoids, flavones, and flavonols were determined spectrophotometrically. The antioxidant properties of the sage leaf extracts were evaluated using five different antioxidant assays (FRAP, DPPH, ABTS, BriggsRauscher reaction, and β‐carotene bleaching). The antimicrobial activity of the extracts was tested against two Gram‐positive (Bacillus cereus and Staphylococcus aureus) and two Gram‐negative (Salmonella Infantis and Escherichia coli) bacterial reference strains. All extracts were extremely rich in phenolic compounds, and provided good antioxidant and antibacterial properties, but the phenophase in which the leaves were collected affected the phenolic composition of the sage extracts and consequently their biological activity. The May Extract, the richest in total flavonoids, showed the best antioxidant properties and the highest antimicrobial activity. Thus, collection of the plants during May seems the best choice for further use of them in the pharmaceutical and food industry.

Antioxidant and vasodilatory effects of blackberry and grape wines.

In contrast to the well-described various biological effects of grape wines, the potential effects of commonly consumed blackberry wine have not been studied. We examined in vitro antioxidant and vasodilatory effects of four blackberry wines and compared them with the effects of two red and two white grape wines. Although some blackberry wines had lower total phenolic content relative to the red grape wines, their antioxidant capacity was stronger, which may be related to a higher content of non-flavonoid compounds (most notably gallic acid) in blackberry wines. Although maximal vasodilation induced by blackberry wines was generally similar to that of red wines, blackberry wines were less potent vasodilators. Vasodilatory activity of all wines, in addition to their flavonoid and total phenolic content, was most significantly associated with their content of anthocyanins. No association of vasodilation with any individual polyphenolic compound was found. Our results indicate the biological potential of blackberry wines, which deserves deeper scientific attention.

Influence of the phenophase on the phenolic profile and antioxidant properties of Dalmatian sage.

This study aimed to research the influence of phenophase on the phenolic profile (phenolic acids, flavonoids and stilbenes) and related antioxidant properties of sage, one of the most characteristic plants of Dalmatian karst. The total phenol and flavonoid contents in sage leaves were determined spectrophotometrically, while the principal phenolics were determined using HPLC-RP-DAD. Antioxidant properties of this well known medicinal plant were determined as free radical scavenging activity (DPPH), ferric reducing/antioxidant power (FRAP) and by Briggs-Rauscher oscillating reaction (BR). The results strongly indicate that Dalmatian sage leaves are rich source of valuable phenolics, mainly phenolic acids, with extremely good antioxidant properties. The presence of resveratrol or its derivatives was confirmed in all extracts. The best results for total phenols and flavonoids, as well as the best antioxidant properties were obtained for May sage, while the highest amounts of catechin monomers and compounds from group of stilbenes were found in February extract.