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In an attempt to find an alternative and potent source of diosgenin, a steroidal saponin in great demand for its pharmaceutical importance, Helicteres isora suspension cultures were explored for diosgenin extraction. The effect of biotic elicitors on the biosynthesis of diosgenin, in suspension cultures of H. isora was studied. Bacterial as well as fungal elicitors such as Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger were applied at varying concentrations to investigate their effects on diosgenin content. The HPLC based quantification of the treated samples proved that amongst the biotic elicitors, E. coli (1.5%) proved best with a 9.1-fold increase in diosgenin content over respective control cultures. Further, the scaling-up of the suspension culture to shake-flask and ultimately to bioreactor level were carried out for production of diosgenin. During all the scaling-up stages, diosgenin yield obtained was in the range between 7.91 and 8.64 mg l -1 , where diosgenin content was increased with volume of the medium. The quantitative real-time PCR (qRT-PCR) analysis showed biotic elicitors induced the expression levels of regulatory genes in diosgenin biosynthetic pathway, the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and cycloartenol synthase (CAS), which can be positively correlated with elicited diosgenin contents in those cultures. The study holds significance as H. isora represents a cleaner and easy source of diosgenin where unlike other traditional sources, it is not admixed with other steroidal saponins, and the scaled-up levels of diosgenin achieved herein have the potential to be explored commercially.

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Helicteres isora L. (Malvaceae) is a medicinal plant highly used in traditional therapeutic practices. It has shown wide-spectrum therapeutic activities including anti-plasmodial, hypoglycemic, hypolipidemic, hepatoprotective, antinociceptive, antioxidant and anti-HIV. Present investigation was undertaken with an objective of establishment of cell suspension cultures of this plant which can be further used for in vitro production of desired secondary metabolites and their further scale-up. Seed dormancy was broken using sulfuric acid and seedlings were raised in vitro. MS medium supplemented with 2,4-D (0.5 mg/L) produced maximum callus from the nodal explants. The callus produced was used as an explant for the establishment of suspension cultures. MS medium without any supplement was proved best for the establishment of cell suspension cultures of H. isora. To the best of our knowledge, this is the first report on H. isora cell suspension culture establishment.

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