Evaluation of antioxidant potential of medicinal plants from Malaysian Rubiaceae (subfamily Rubioideae)

Abstract

This paper evaluates the antioxidant potential of 22 species of medicinal plants from Malaysian Rubiaceae. The ferric thiocyanate (FTC), thiobarbituric acid (TBA), total phenolic content (TPC) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays were employed. The tested extracts showed strong antioxidant potential when compared to butylated hydroxytoluene (BHT), quercetin and vitamin E with percent inhibition of 91 - 99% in the FTC, and 77 - 97% in the TBA assays. The TPC of extracts found varied from 8.55 to 120.63 mg_GAE/g_PE. Psychotria griffithii and Hydnophytum formicarum showed total phenolic content of more than 100 mg_GAE/g_PE and strong DPPH radical-scavenging activity with IC₅₀ values of 14.0 and 22.4 μg/ml, respectively. The standard vitamin C and BHT showed IC₅₀ values of 12.8, and 5.6 mg/ml, respectively. A good correlation was observed between total phenolic content and radical-scavenging activities. The medicinal plants in this study tested are expected to be good sources of natural antioxidants.

Keywords: Antioxidant, Rubiaceae, ferric thiocyanate (FTC), thiobarbituric acid (TBA), 1,1-diphenyl-2-picrylhydrazyl (DPPH), total phenolic content (TPC)