Antioxidant and antidiabetic activity of Thymus quinquecostatus Celak

The present study was conducted to evaluate the antioxidant, antimicrobial, and antidiabetic activities of methanol extract of Thymus quinquecostatus Celak and those of its partitioned fractions, including hexane, ethyl acetate, n-butanol, and aqueous. The antioxidant activities of the TQC extract were measured by 1,1-dephenyl-2-picryl-hydrazyl free radical scavenging and a reducing power assay. The antidiabetic activity was evaluated by alpha-glucosidase and alpha-amylase inhibition assays. The results suggested that the ethyl acetate (EtOAc) fraction of the MeOH crude extract possessed strong antioxidant activity and capacity. In addition, the EtOAc fraction showed remarkable antimicrobial activity against Kocuria rhizophila (MIC = 63 mu g/ml) and Staphylococcus epidermidis (MIC=63 mu g/ml). The findings also indicated that the MeOH crude extract and its EtOAc fraction contained strong antidiabetic activity. HPLC analysis identified (-)-catechin, chlorogenic acid, rutin, and rosmarinic acid as the active compounds in the TQC extract. The alpha-glucosidase inhibitory activity in the hexane fraction was positively associated with the amount of thymol. Taken together, these results suggest that the TQC extract could be exploited as an ingredient in antioxidant and antidiabetic supplements and in drugs to treat infectious diseases. (C) 2013 Elsevier B.V. All rights reserved.