Medicinal plants contain a wide variety of antioxidants, which may provide protection against the development of several diseases. Antioxidant properties and total phenolic content of methanolic extracts from different parts of thirteen spices belonging to six botanical families grown in botanical garden of Mashhad were investigated. Studied species includes Ballota nigra (leaves), Dipsacus laciniatus (leaves and flower), Eryngium caucasicum (roset leaves and flowering shoots), Grindelia robusta (leaves and flowers), Marrubium Vulgare (leaves), Origanum vulgare subsp. virid (flowering shoots), Phlomis fruticosa (leaves), Sanguisorba minor (leaves) and Stachys byzantina (leaves). The antioxidant capacity was evaluated by two methods: DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ferric reducing/antioxidant power (FRAP). The total phenolic content was measured using a Folin–Ciocalteu assay. Extract yield for each plant was also determined. Results indicated that flowering shoots of Origanum vulgare subsp. virid have the highest amount of total phenolic content and the highest antioxidant activity in FRAP method. In addition, the lowest amount of total phenolic content and the lowest antioxidant activity (FRAP) was related to Eryngium caucasicum. Among species, Phlomis fruticose showed the lowest IC50 which means had the highest antioxidant activity (DPPH method). A positive strong correlation (p≤0.01) was observed between total phenolic content and FRAP results, which suggests that polyphenols in the extracts are mostly responsible for the antioxidant activities. Based on results, leaves of Grindelia robusta showed the highest extract yield (0.19 g). In conclusion, so called medicinal plants, could be considered as a valuable resource for natural antioxidants and good alternative for synthetic antioxidants.

Keywords