The results imply that the antioxidants in these plants are capable of scavenging free radicals and reducing oxidants. The high correlation between the antioxidant and activities and their TPC and TF indicates that phenolic compounds are the major contributor of antioxidant capacities of these plants. The extract of Ya-hom Intajak and its fractions possesses significant antioxidant activity on LDL oxidation, indicating that the extract contained compounds that were relatively strong inhibitors of LDL peroxidation. The plants are valuable sources of natural antioxidants.