| Solasodine belongs to a class of steroidal alkaloids, which consist of steroids (e.g., cholestane, pregnane) incorperating nitrogen in their chemical strucutres. The source of nitrogen is believed from L-arginine, which is used for the amination via the substitution on 26-hysroxycholesterol. The second hydroxylation leads into 26-amino-22-hydroxycholesterol, which can be cyclized, yielding a piperidine ring structure. Following 16 beta-hydroxylation, the spiro-structure can be formed via a nucleophilic reaction, leading into 22R (solasodine) and 22S (tomatidine) isomers as well as solanidine (with an indolizidine ring). In the biosynthetic pathway of steroidal alkaloids, there is a close association between steroidal alkaloid synthesis and enzymatic activities of terpenoid biosynthesis. In Solanum and other species, there are several types of steroidal alkaloids; solasodine-type steroidal alkaloids (e.g., solasodine, solasonine), tomatidine-type steroidal alkaloids (e.g, tomatidine, tomatine) and solanidane-type steroidal alkaloids (e.g., solanidine, demissidine, alpha-solanine, alpha-chaconine), and these steroidal alkaloids usually exist in glycosylated forms (e.g., alpha-chaconine, alpha-solanine, tomatine). In Solanum melongena (eggplant), solasodine-type steroidal alkaloids are dominant steroidal alkaloids (e.g., solasodine, solasonine, solamargine). Some of steroidal alkaloids are reported to have acetylcholinesterase inhibitory, positive inotropic and teratogenic activities. |
