Trolox-equivalent antioxidant capacity and composition of five alpine plant species growing at different elevations on the Qinghai–Tibetan Plateau

Background: Alpine plants on the Qinghai–Tibetan Plateau are exposed to an extremely harsh environment, namely severe cold, strong ultraviolet radiation, hypoxia and low CO₂ partial pressure. These conditions are sources of oxidative stress, which increase in severity with increasing elevation. Aims: To examine whether antioxidant capacity and chemical composition of alpine plants change with increasing elevation. Methods: We measured the Trolox-equivalent antioxidant capacity (TEAC) and chemical composition of five alpine plant species at 3016, 3814 and 4621 m a.s.l. Results: With increasing elevation: (1) the TEAC increased and total phenols and tannins tended to increase in two forb and two shrub species but not in a sedge species; (2) concentrations of protein and fat increased in all five plant species; (3) polyunsaturated fatty acids (PUFA) increased and (4) mineral concentrations tended to decrease, but trends were inconsistent. Conclusions: We conclude that with increasing elevation, TEAC and total phenols and tannins increased which we interpreted as an adaptation to higher oxidative stress; and protein and fat contents increased to support high metabolic activity. The increase in PUFA and the trend for minerals to decrease with increasing elevation require further investigation.