Tocopherols and triterpenoids from Sida acuta

A new tocopherol derivative, 7(a)-methoxy-alpha-tocopherol (1), and a new taraxastane triterpene, taraxast-1,20(30)-dien-3-one (5), together with four known compounds, beta-tocopherol (2), alpha-tocopherol (3), alpha-tocospiro B (4) and taraxasterone (6) were isolated from the whole plant of Sida acuta. Their structures were elucidated by spectral analysis including MS, 1D and 2D-NMR spectroscopy. Among those compounds, compounds 1, 2, and 3 showed significant antioxidant effect (EC50 = 86.9, 68.2, and 70.9 mu M, respectively) in the DPPH radicals scavenging activity assay.