Screening of Thai Medicinal Plants for Free Radical Scavenging and DNA Protective Properties

Abstract

Twenty-one methanolic extracts prepared from 20 plant species were examined for their free radical scavenging activity and DNA protective property. Assays for free radical scavenging activity were conducted using two chemical species, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and superoxide anion.  Evaluation for DNA protective activity was performed on pBR322 plasmid DNA in the presence of photosensitized riboflavin.  Trolox was used as the positive control in all experiments. At the concentration of 100 mg/mL, ten plant extracts showed higher than 50 % inhibition against DPPH and superoxide radicals, with the bark extract of Peltophorum dasyrachis being the most potent sample. When these 10 plant extracts were further tested for their inhibitory activity against DNA strand breakage, nine exhibited greater than 70% inhibition, and were then selected for IC₅₀ determination. The extract prepared from Artocarpus gomezianus leaves exhibited the most promising DNA protective activity, with a potency about 14-fold greater than that of Trolox. The fruit extract of Cochlospermum  religiosum and the bark extract of Peltophorum dasyrachis were also interesting, showing strong inhibitory effects on DNA breakage.