Evaluation of antioxidant potential of medicinal plants from Malaysian Rubiaceae (subfamily <i>Rubioideae</i>)

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)