Tocopherols and Triterpenoids from Sida acuta

A new tocopherol derivative, 7a-methoxy-a-tocopherol (1), and a new taraxastane triterpene, taraxast-1,20(30)-dien-3-one (5), together with four known compounds, β-tocopherol (2), α-tocopherol (3), α-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 (EC 50 = 86.9, 68.2, and 70.9 μM, respectively) in the DPPH radicals scavenging activity assay.