Bioactive secolignans from Peperomia dindygulensis.

Thirteen secolignans, including eight new ones (1-8), were isolated from the EtOAc extract of Peperomia dindygulensis. The structures were mainly elucidated by 1D and 2D NMR and MS experiments, the relative configurations were determined by NOE correlations, and the absolute configurations were established by the optical rotations and CD spectra. Cytotoxicity and MDR (multidrug resistance) reversal activity of the isolated compounds were examined.

In vitro cytotoxicity of the protoberberine-type alkaloids.

In vitro cytotoxic activities of 24 quaternary protoberberine alkaloids related to berberine have been evaluated using a human cancer cell line panel coupled with a drug sensitivity database. Extending the alkyl chain at position 8 or 13 strongly influenced the cytotoxic activity, that is, relative lipophilicity as well as the size of the substituent affects cytotoxicity. The highest level of activity was observed in 8- or 13-hexyl-substituted derivatives of berberine.