Updates on steroidal alkaloids and glycoalkaloids in Solanum spp.: Biosynthesis, in vitro production and pharmacological values

Solanum is one of the largest genera of the family Solanaceae comprising > 2000 species distributed mostly in the tropical and subtropical regions of Australia, Africa, and some parts of Asia, such as China, India, and Japan. The nutraceutical and pharmaceutical values of the Solanum species are due to the presence of bioactive phyto-constituents such as steroidal saponins, steroidal alkaloids, terpenes, flavonoids, lignans, sterols, phenolic compounds, coumarins, etc. Among them, the presence of steroidal alkaloids and glycoalkaloids serves as major chemical markers of this genus. Steroidal alkaloids and glycoalkaloids have a special status in traditional and modern systems of medicine possessing a wide range of bioactivities, viz., antimicrobial, analgesic, hepatoprotective, immunomodulatory, anticancer, neurogenetic, etc. Steroidal alkaloids (STAs) are the major class of secondary metabolites found not only in plants but also in higher animals as well as in some aquatic invertebrates. They have a steroidal (cyclopentanophenanthrene) backbone skeleton with a nitrogen atom. The biosynthesis of these alkaloids takes place from steroids or triterpenoid pathway, on the basis of which they are further divided into different classes and subclasses. The present review is focused on the occurrence and biosynthesis of steroidal alkaloids in Solanaceae family. These compounds are mainly triterpene-derived molecules that are involved in various defense responses participating also in formulations of a wide range of phyto-pharmaceuticals. The addition of sugar moieties to the base skeleton by glycosyltransferases resulted in the formation of steroidal glycoalkaloids (STGAs), possessing a wide range of pharmacological values. The accumulation of these bioactive metabolites has been shown to be highly influenced by environmental and geographical factors. Hence, their production via tissue culture always offers an attractive alternate production platform. The current trends and biotechnological tools recently developed for the sustainable production and up-scaling of these bioactive constituents are focused in the present review.