Malabaricone C （1）, isolated from the seeds ofMyristicafragrans Houtt., belongs to a kind of diarylnonanoid compounds that are only found in Myristicaceae till now. In this study, biotransformation of 1 was investigated using rat hepatic microsomes for the first time and the main biotransformation product was elucidated as malabaricone B （2） according to the spectroscopic data. Further evaluation on human gastric cancer cell lines showed that the cytotoxic effects of malabaricone C and its metabolite malabaricone B were comparable to those of vinorelbine, with the values of IC50 of （42.62±3.10） and （19.80±1.70） μg/mL on NCI-N87, and （22.94±1.33） and （19.60±2.21） μg/mL on MGC803, respectively. Statistical analysis revealed that malabaricone B had significantly stronger cytotoxicity than the parent compound （P〈0.01 on NCI-N87 and P〈0.05 on MGC803）, which may indicate a bioactivation of malabaricone C by hepatic microsomes. These results suggest that malabaricone C has a simple biotransformation pathway by hepatic microsomes and provide valuable information for further investigation on both the parent compound and its biotransformation product as anti-gastric cancer agents or lead compounds.
