APPLICATION OF THIN LAYER CHROMATOGRAPHY IN THE STUDY OF NATURAL PRODUCTS Ⅰ. IDENTIFICATION OF ERGOMETRINE ERGOTAMINE AND ERGOTOXINE

The present paper reports investigations of thin layer chromatography for the identification of ergot alkaloids, using alumina without binder. As dictated by the physico-chemical properties of ergot alkaloids and the usual characteristics of thin layer chromatography, studies on factors influencing R_f values and shape of spots of ergometrine, ergotamine, and ergotoxine have been carried out. Good separation was obtained with acidic, neutral as well as weakly basic alumina. Alumina with particle sizes of 120—160, 160—200 and below 200 mesh were compared, the best result being obtained with the last size, producing round and sharp spots. Mixtures with various ratios of petroleum ether-benzene-absolute alcohol and of benzene-chloroformabsolute alcohol were used and mixture of benzene-absolute alcohol (10:0.5) was found to be the best, with R_f values 0.10, 0.33 and 0.50 for ergometrine, ergotamine, and ergotoxine respectively. The composition of this solvent mixture is rather simple and amenable to ready recovery. The angle of inclination made by the plate had no great influence, although the most suitable was found to be between 8—16°. "Edge effect" may be avoided by tightly covering the container for 10 minutes to assure saturation with the solvent vapours before immersing the lower end of the plate. According to these results, a thin layer chromatographic method for the identification of ergot alkaloids has been proposed, which gave identical results as paper chromatography when tested with eight ergot samples.