Antioxidant and scolicidal activities of four Iranian Mentha species (Lamiaceae) in relation to phenolic elements

Introduction: There is a growing interest of industry to replace synthetic chemicals by natural products with bioactive properties from plant origin. The present study reported the antioxidant activity and scolicidal effects of the crude extracts from Mentha spicata, M. aquatica, M. longifolia, and M. × piperita var. citrata growing in Iran. Methods: Total phenolic, flavonoid and flavonol contents of the four Mentha taxa were examined. Two antioxidant assays i.e. free radical scavenging activity (DPPH assay) and reducing power assay were used for determining the antioxidant capacity of the alcoholic extracts. Scolicidal activity of serial dilutions (۱۵–۲۰۰ mg/mL) of Mentha extracts was evaluated after ۱, ۵, ۱۰, ۲۰ and ۳۰ minutes of exposure time. Results: Methanol was the solvent yielding the highest values of total phenolic (TPC), flavonoid (TFC) and flavonol contents (TFvC). On the other hand, the extracts from M. × piperita var. citrata gave the highest total phenolic content (۱۹۱.۶ mg gallic acid equivalent per g; GAE/g), total flavonoid content (۵۷.۰ mg quercetin per g; QE/g) and total flavonol content (۱۵.۳ mg QE/g) values. The methanol extracts of M. × piperita var. citrata also gave the strongest DPPH radical scavenging activity (۸۳.۲%), whereas the reducing power yielded absorbance values between ۰.۱۸۹ in M. spicata and ۱.۱۶ in M. × piperita var. citrata. The highest scolicidal activity (۹۹.۵۴%) was observed in ۲۰۰ mg/mL methanol extract of M. aquatica after ۳۰ minutes of application. Conclusion: Overall, M. × piperita var. citrata and M. aquatica could be the taxa of choice for future supplementary studies.