Antioxidant activity was measured in 14 plant species incorporated in more than 30% of Tibetan medicines used for cardiovascular disease and related symptoms according to indigenous pharmacopoeias. The study was undertaken in order to explore possible dietary/medicinal elements which may contribute to the reportedly low incidence of cardiovascular disease among Tibetan highlanders despite high hematocrit levels and a high saturated fat/low fruit and vegetable diet. Extracts of Terminalia chebula, Syzygium aromaticum, Aquilaria agallocha, Santalum album, Amomum subulatum, Justicia adhatoda and Myristica fragrans were strong scavengers of the 1,1 diphenyl-2-picryl-hydrazyl (DPPH) radical (P < 0.05). Cu2+-catalyzed low-density lipoprotein (LDL) oxidation was measured in vitro using thiobarbituric acid reactive substances (TBARS) formation and monitoring change in absorbency at 234 rim from conjugated dienes. The hexane fraction of S. aromaticum significantly reduced LDL susceptibility to oxidation (1339.96 +/- 7.01 min. lag time, P < 0.05), more than three times longer than TroloxRTM (431.02 +/- 21.19 min). Results of TBARS (90 min.: r = 0.71, P < 0.005; 180 min.: r = 0.74, P < 0.005) and DPPH (r = 0.69, P < 0.05) assays positively correlated to conjugated dienes formation. Our results suggest that these plants are likely to contribute to the therapeutic effects of traditional drugs used to treat cardiovascular disease.

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