Antioxidant activity and phenolic content of Orthosiphon stamineus Benth from different geographic

The antioxidant activity and the total phenolics content of methanol extracts of Orthosiphon stamineus, Benth (Lamiaceae) obtained from different localities were determined. The antioxidant properties were evaluated by measuring scavenging effect on 2,2-diphenyl-1- picryhydrazyl (DPPH) radical and beaching rate by (β-carotene/linoleic acid system. The extracts from all locations showed antioxidant activity comparable to that of pure quercetin and higher than that of widely used synthetic antioxidant butylated hydroxylanisole (BHA). Some of the locations exhibited significant differences (P 0.05) from one location to another of antioxidant value in both assays. Total phenolics content of the extracts were determined to correlate with their antioxidant activity. However, at 2 mg/mL, there was poor correlation between the total phenolic content and antioxidant activity by DPPH radical scavenger and (β-carotene/linoleic acid bleaching method (r^2= 0.42 and 0.048, respectively). Therefore, the antioxidant activity of Orthosiphon stamineus extracts is not solely due to the phenolics compounds.