Phenolic Content, Antioxidant Effects and Tyrosinase Inhibitory Activity of Extract of Some Stachys Species from Iran

Given the importance of Stachys genus in Iran and their significant biological activity, we collected three species of this plant: St. aucheri Benth., Stachys benthamiana Boiss and St. inflata Benth. from different regions of Iran. We examined the free radical scavenging potential, total phenol content and tyrosinase inhibitory activity of their methanol, methanol 80% and dichloromethane extracts.

Antioxidant activity and total phenol content of the mentioned extracts were assessed using DPPH and FolinCiocalteu reagent, respectively. The inhibitory activity of the extracts on tyrosinase was also investigated.

Total phenol content of different extracts was high in the extracts as 98.5-139.7 mg eq. gallic acid/g in methanol 80% extract, 36.8-54.7 mg eq. gallic acid/g in methanol extract and 17.9-44.9 mg eq. gallic acid/g  in dichloromethane extract. Furthermore, their antioxidant activity was correlated with total phenol content of the extracts. Methanol 80% extract had the highest total phenol content and antioxidant activity. Evaluation of the tyrosinase inhibitory potential of the extracts revealed that St.inflata exhibited a considerable inhibitory potential (IC50= 5.4 ± 0.6 µM).

It can be concluded that tyrosinase inhibitory activity of Stachys genus might be due to the less polar compounds and these compounds are mostly present in the dichloromethane extract of St. inflatai over St. aucheri and St. benthamiana