DESMODIUM ALKALOIDS

Abstract

Twelve alkaloids (I–XII) comprising of four broad structural types, viz., carboxylated and decarboxylated tryptamines, β–carbolines and β–phenethylamines, have been isolated from different parts of Desmodium gangeticum DC at different stages of its development. Two alkaloids, viz., (IX, X), were previously unreported in nature. The occurrence of candicine (VIII) in a leguminous plant is also a new observation.

The alkaloid versatility of D. gangeticum points it to be a phylogenetically well developed species in the sub–family Papilionaceae. The significance of alkaloid information in the systematic classification of plants belonging to the genus Desmodium has also been demonstrated.

Pharmacological screening was conducted with the total alkaloids from different parts of the plant to examine the validity of the reported uses of the plant extracts in the Indian system of medicine. Four major responses were discernible from the examination of alkaloids from the aerial portions. These are anticholinesterase, smooth muscle stimulant, CNS stimulant and depressor responses. The presence of catecholamine liberators (fert–β–phenethylamines) and candicine in the roots is responsible for a nicotinelike effect on dog's intestine in situ and carotid blood pressure. The results would seem to indicate that the medicinal properties of the plant essentially reside in the contained alkaloids.