摘要:
(Z)-2,2-Dimethyl-8-(3-methyl-2-butenyl) acid (1) was isolated from Brazilian propolis, together with-the known benzopyran derivative, (E)-2,2-dimethyl-8-(3-met-2-butenyl)-benzopyran-6-propenoic acid (2). The structure was determined by spectroscopic analyses, which included 1D and 2D H-1 and C-13 NMR experiments, as well as MS, IR, and UV spectroscopy, Compound 2 rapidly changed to 1 under UV irradiation conditions (365 nm), and. the reverse reaction was also observed. The ratio of 1 to 2 reached 2.3 when the reaction began from either 1 or 2, indicating a photostationary state. Compound 1 displayed an approximate 7-fold stronger cytotoxicity against human lung carcinoma cells (HPLC-2) compared with 2.