engleski

Medicinal plant extracts with good antioxidant properties as a source of resveratrol derivatives

ABSTRACT Introduction In recent years, there has been a world wide trend towards the use of natural phytochemicals present in fruits, vegetables and herbs. With the purpose of reducing the risk of various diseases consumer is advised to enrich the nutrition with bioactive compounds with good antioxidant properties. The results of our past research confirm that individual medicinal plants can be valuable source of natural antioxidants in nutrition (Katalinić et.al. Food Chemistry 2006). The purpose of this study was to examine the polyphenolic composition including the presence of resveratrol derivatives, and antioxidant potential of seventeen medicinal plants traditionally used in Croatian folk medicine. Material and Methods Samples of medicinal plants were purchased from a local pharmacy or market. The total phenolic content was measured using a Folin-Ciocalteu assay. Total antioxidant capacity of ethanolic plant extracts was estimated as DPPH radical scavenging ability and ferric reducing/ antioxidant power (FRAP). Stilbene polyphenols were analyzed by HPLC-RP. Results and Discussion Significant differences in phenolic composition and antioxidant properties of analyzed plant extracts were confirmed, as expected. The total phenolic contents ranged from 2042 to 30782 mg gallic acid equivalents (GAE)/L. The best results were obtained for Vitis idaei folium extracts. All plant extracts exhibited excellent antioxidant properties. When percent of DPPH radical inhibition was compared at equal concentration value of total phenols (100 mg GAE/L) it ranged from 8.43 to 91.03 %. FRAP ranged from 0.073 to 1.098 mmol/L Trolox equivalents. Vitis idaeae folium, Mirtilli folium, Fragariae folium, Salviae folium, Helichrysi flos, and Teucrii montani herba extracts showed the best DPPH and FRAP results. HPLC separation indicated the differences in the polyphenolic composition of plant extracts. Among the analyzed plant material the Teucrii montani herba, Salviae folium, and Fragariae folium extracts can be considered the best sources of resveratrol derivatives. Free resveratrol monomers, if found, were present in very small amounts, mostly as E-isomer.

Medicinal plants; Stilbene polyphenols; HPLC; Antioxidative properties

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