Further fractionation and co-promoting activity of the large molecular weight components of aqueous tobacco extracts.

Earlier studies showed that aqueous extracts of tobacco exhibit tumor promoting activity. The activity required the simultaneous presence of two agents, one of which was methanol soluble and the other, methanol insoluble. In this study, the 80% methanol insoluble fraction was further fractionated using dialysis through controlled pore membranes. Each resulting sub-fraction was then combined with the methanol soluble fraction and tested as a promoting stimulus in mice treated with 7,12-dimethylbenz[a]anthracene. The subfraction (D) with a presumptive molecular weight greater than 13,000 produced a significantly higher tumor incidence and tumor yield together with a significantly shorter latent period than the other subfractions. D contained about 12% of the total 80% methanol insoluble material. All of the other subfractions exhibited significant but less pronounced co-promoting activity.