A study of betel quid carcinogenesis. 1. On the in vitro N-nitrosation of arecoline.

Betel quid chewing is strongly associated with cancer of the oral cavity. Extracts of betel quid are tumorigenic in the experimental animal, but thus far, not a single carcinogen has been detected in the tobacco free quid. This study is based on the hypothesis that during chewing, arecoline, the major alkaloid of the betel nut, gives rise to carcinogenic N-nitrosamines. In vitro experiments reported here have shown that N-nitrosation of arecoline leads to N-nitrosoguvacoline (NG), 3-(methylnitrosamino)propionitrile (MNPN) and 3-(methylnitrosoamino)propionaldehyde. Although, according to an earlier study. NG is most likely not carcinogenic, MNPN is suspected to be a relatively strong animal carcinogen based on bioassays with its lower homologue. The conditions prevailing in the oral cavity of betel quid chewers are likely to favor the formation of these three nitrosamines.