Relative sterol composition in the genus Nicotiana.

Stigmasterol, β-sitosterol, campesterol, and cholesterol are the predominant sterols identified by gasliquid chromatographic techniques in the mature leaves of 50 Nicotiana species. The relative composition pattern of the four sterols varies significantly among the subgenera as well as within the subgenus. However, six N. tabacum cultivars showed a similar pattern, of which as an average stigmasterol represents the highest proportion (43%) followed by β-sitosterol (30%), campesterol (19%), and cholesterol (8%) in total sterol content. Negative correlations were obtained for the composition of stigmasterol vs. β-sitosterol, cholesterol vs. campesterol, and cholesterol vs. β-sitosterol. Some correlations between geographic distribution of Nicotiana species and sterol composition were evident. In evaluating phylogenetic relationship between amphiploid species and the possible diploid progenitors, the results of sterol composition are in favor of N. undulata and N. paniculata being the ancestors of N. rustica and the N. sylvestris X N. tomentosiformis as the hybrid combination from which N. tabacum was evolved.