ARAROBA POWDER, a drug occurring as a yellowish brown powder, varying in tint, which derives an alternative name —Goa powder—from the Portuguese colony of Goa, where it appears to have been introduced about the year 1852. The tree which yields it is Andira araroba of the natural order Legumi nosae. It is met with in low and humid spots in the province of Bahia. The tree is from 8o to 1 oof t. high and has large imparipinnate leaves, the leaflets of which are oblong, about I2in. long and fin. broad, and somewhat truncate at the apex. The flowers are papilionaceous, of a purple colour and arranged in panicles. The Goa powder or araroba is contained in the trunk, filling crevices in the heartwood, and yields to hot chloro form 5o% of crude chrysarobin, which has a definite therapeutic value and is contained in most modern pharmacopoeias. It occurs as a micro-crystalline, odourless, tasteless powder, very slightly soluble in either water or alcohol which contains pure chrysa robin (C15H1203), di-chrysarobin methylether di-chrysarobin (C3oH2407). Chrysarobin is a methyl trioxyanthra cene and exists as a glucoside in the plant, but is gradually oxidized to chrysophanic acid (a dioxy-methyl anthraquinone) and glucose.
The drug is a powerful irritant. Modern dermatologists use only chrysophanic acid, which may be applied externally and given by the mouth in doses of about one grain in cases of psoriasis and chronic eczema.