Isolation and Structure of Rosamine — a New Pseudoindoxyl Alkaloid from Catharanthus roseus

Leaves of Catharanthus roseus (L) G. Don (72 kg) were collected from a field grown in the Karachi Uni­ versity campus. The crude alkaloids (134 g) obtained from the alcoholic extract of the air-dried leaves (24 kg) of the plant, were dissolved in chloroform (450 ml) and extracted with pH 3 phosphate buffer (1 1). The chloroform layer was dried (anhydrous Na2S 0 4), concentrated to 1/3 of its original volume and petroleum ether (320 ml) added to the chloroform solution which caused some of the alkaloids to pre­ cipitate out. The precipitates were filtered, and the filtrate was again concentrated to a gum (40 g). The gum was dissolved in ethyl acetate (200 ml) and ex­ tracted with pH 2 phosphate buffer (11). The aqueous layer was separated, washed with chloroform, basified with ammonia to pH 10 and again extracted with chloroform (1.5 1) to afford fraction F I (22 g). This fraction was chromatographed on an alumina column (220 g) elution being carried out with ethyl acetate (5 1). The eluates were concentrated (12 g) and again loaded an another column of t.l.c. grade silica (36 g). The column was eluted with increasing polarities of petroleum ether, ethyl acetate, and ethyl acetate-methanol. Elution with ethyl acetate-methanol (9:1) afforded an alkaloid-containing fraction, which was concentrated and subjected to preparative