In this study, the in vitro antioxidant activity of the methanolic extracts of leaves and flowers of Ipomoea cairica and leaves of Ageratina adenophora were determined by spectrophotometric method. Antioxidant activity of extracts were expressed as percentage of DPPH radicals inhibition and IC50 values (μg/ml). Values in percentage ranged from 2.70 % for 0.0005 mg/ml concentration of I. cairica leaves to 93.24% for 0.05 mg/ml concentration of I.cairica flowers. The largest capacity to neutralize DPPH radicals was found for methanolic extract of I.cairica flowers which neutralized 50% of free radicals at the concentration of 1.00 μg/ml. I. cairica can be regarded as promising candidates for natural plant sources of antioxidants with high value.