Phenolics and related biological properties of Dalmatian sage collected in different phenophases

Consumer demands for safe, stable and naturally preserved food products have intensified research of different plant phenolic extracts which are known to possess antioxidant activity and offering a potential alternative to synthetic preservatives. This study aimed to research the influence of phenophase on the phenolic profile and related antioxidant properties of sage, one of the most characteristic plants of Dalmatian karst. Sage leaves were picked up in different phenophases (February, May, August and November) at the area of the Vrana Lake Nature Park (Middle Dalmatia, Croatia). Total phenols, flavonoids, non-flavonoids, flavons and flavanols in sage extract were determined using spectrophotometric methods. The antioxidant potential of extracts was evaluated, in vitro, using five different antioxidant methods (FRAP, DPPH, ABTS, BR, β-carotene bleaching method). Significant differences in phenolic composition and antioxidant properties of analyzed sage extracts were confirmed, as expected. The total phenolic contents ranged from 4.34 to 5.16 g GAE/L. The best results were obtained for May extract. Relative content of flavonoids was around 17 % in May extract, while during rest of the year it ranged from 4 to 9 %. The content of flavones and flavonoles was also the highest in May extract. All plant extracts exhibited excellent antioxidant properties. The best antioxidant results using all methods (free radical scavenging ability, reducing power, the efficiency in protecting the oxidation of linoleic acid and inhibition of oscillations) were obtained for May extract. We can conclude that good antioxidant properties of Dalmatian sage leaves are a result of very high content of phenolic compounds, especially flavonoid fraction. Determined differences in phenolic composition and biological activity of sage extracts show greatest phenolic potential and best antioxidant properties for May leaves extracts, making it the best choice for further use as functional food ingredient.