Tarennane and tarennone, two novel chalcone constituents from Tarenna attenuata.

Two novel chalcone constituents, tarennane (1) and tarennone (2), together with nine known compounds, were isolated from the whole plant of Tarenna attenuata. By analysis of physical and spectroscopic data, the structures of new compounds were elucidated as (E)-4-[3-(4-hydroxy-3-methoxyphenyl)-acryl]-3,4,5-trimethoxycyclohexa-2,5-dienone (1) and 1,2-bis(3,5-dimethoxy-4-hydroxyphenyl)-3-hydroxypropan-1-one (2). These two compounds were tested for antioxidant activities in the MTT and DPPH assays. Compound 1 revealed potent antioxidant activities against H2O2-induced impairment in PC12 cells, but neither of them showed DPPH radical-scavenging activity with IC50 values of 181.1 and 210.3 microM, respectively.