New Terpenoids and Lignans from <em>Phyllanthus acidus</em> Fruits with Antioxidant Activity

The fruits of Phyllanthus acidus, rich in various secondary metabolites and possessing significant antioxidant activity, have been consumed widely by many Southeast Asian people, including the Thai, Vietnamese, Burmese, Laotians, Cambodians. The extensive investigation on the chemical constituents of the fresh fruits led to the isolation and identification of 17 compounds including four new compounds (1-4). Their structures were elucidated on the basis of the extensive spectroscopic analyses. The absolute configurations of 1, 3, 4 were determined by comparison of their experimental electric circular dichroism (ECD) curves with references and calculated ECD spectra. Notably, the known lignan 13 and phenylpropanoid 15 showed obvious ABTS+ radical scavenging activities with IC50 values of 203.7 and 232.9 uM, respectively, which are comparable to the positive control, Trolox (IC50 = 176.5 ± 2.0 uM). The results indicated that P. acidus fruits can be a promising sources of antioxidant food supplement.