Antiradical and antilipoperoxidative effects of some plant extracts used by sri lankan traditional medical practitioners for cardioprotection

Reactive oxygen species (ROS) are implicated in many pathogenic processes i ncluding the cardiovascular system. Detoxification of ROS by antioxidants ( AO) therefore affords protection against such diseases. There is a growing body of evidence suggesting that antioxidants contribute to cardioprotectio n. Therefore, nine plants that are components of Ayurvedic formulations use d for the therapy of cardiovascular diseases were investigated to determine whether antioxidant activity is one of the mechanisms by which these plant s exert cardioprotection. Initially aqueous freeze dried extracts of the plants were prepared and the antioxidant activity was measured (a) in vitro, by DPPH (1,1-diphenyl-2-pi crylhydrazyl) radical scavenging and deoxyribose damage protection assays, and (b) in vivo, by effects on lipid peroxidation. Terminalia arjuna showed significant DPPH radical scavenging activity with EC50 8.3 +/- 0.3 mug/mL (similar to L-ascorbic acid). The potency of this activity was much lower i n Cassia fistula (EC50 = 59.0 +/- 2.7 mug/mL). The other seven extracts dem onstrated no such activity in the concentration range tested. In the deoxyr ibose damage protection assay, T. arjuna demonstrated no significant effect in the concentration range 0-20 mug/mL, but above 20 mug/mL concentration (20-125 mug/ml), a pro-oxidant activity was observed (although markedly les s than demonstrated by L-ascorbic acid). A similar trend was observed with Vitex negundo. In contrast, C fistula afforded a 30% protection against suc h damage at 125 mug/ml, concentration. Other plant extracts did not show an y activity in this assay. At a dose of 90 mg/kg (single dose) T. arjuna, ca rdiac lipid peroxidation in mate Wistar rats was reduced by 38.8% +/- 2.6% (p <0.05) whereas the reduction was only 11.6% +/- 3.5% in the case of C fi stula even at a dose of 120 mg/kg. Of all the plants tested, T. arjuna demonstrated the highest antioxidant ac tivity. Overall results show that only some plants used in the therapy of c ardiovascular disease exert their beneficial effects via antioxidant activi ty. Copyright (C) 2001 John Wiley & Sons, Ltd.