Effect of seed number and fruit weight on content and localization of glycoalkaloids in Solanum khasianum

Isolation of solasodine and other steroidal alkaloids and sapogenins by direct hydrolysis-extraction of Solanum plants or glycosides therefrom

Concomitant extraction and hydrolysis of Solanum steroidal glycoalkaloids in a two-phase system containing an aqueous mineral acid and an organic water immiscible solvent, and having a boiling point under 100(o)C, is described. It is essentially a "one-pot" process, combining direct acid hydrolysis of the glycosides in the plant material and in situ extraction of the released aglycones after alkali treatment, in a single step, the various ingredients being added simultaneously or sequentially, as required. Application of the process to fruits, leaves, and tissue cultures of Solanum khasianum Clarke plants, either fresh or in dried, finely ground form, using a two-phase aqueous hydrochloric acid-toluene system, proved to be very suitable for continuous production of pure solasodine which is a valuable raw steroid for the preparation of steroidal drugs. Pure Solanum glycoalkaloids were also prepared and hydrolysed accordingly. The process has analytical applications too, and could be extended in a general way to glycosides in other series for preparation of their related aglycones.

Developmental toxicology of solamargine and solasonine glycoalkaloids in frog embryos

As part of an effort to improve the safety of plant foods, a need exists to define the relative toxicities of structurally different glycoalkaloids and metabolites which may be present in Solanum plant species such as potatoes, tomatoes and eggplants. The objectives of this study were to determine the relative toxicities and the modes of action of the eggplant (Solanum melongena) glycoalkaloids solamargine and solasonine in Xenopus laevis frog embryos, using membrane potential and embryo growth and teratogenicity assays. In the cell membrane assays, adverse effects on embryos were evaluated by measuring membrane potentials using an electrochromic dye, di-4-ANEPPS, as a fluorescence probe for the integrity of the membranes. In the embryo growth and teratogenesis assays, the survival of the embryos and organ malformations was used as an index of embryo toxicity. The relative potencies of glycoalkaloids are similar for frog embryo effects (survival and teratogenicities) and for membrane effects (membrane potential). Experiments with solasonine at pH 6 and 8 suggest that the unprotonated form of the glycoalkaloids appears to be involved in the membrane effects. The nature of the carbohydrate side-chains of the steroidal glycosides governs relative potencies. The possible significance of the findings to food safety and plant physiology and possible application of the membrane assays to bacterial toxins are discussed.

The effect of some Solanum steroidal alkaloids and glycoalkaloids on larvae of the red flour beetle, Tribolium castaneum, and the tobacco hornworm, Manduca sexta

Evaluation of the inhibitory effect of a series of secondary plant compounds including steroidal alkaloids and glycoalkaloids on larvae of the red flour beetle, Tribolium castaneum, was investigated. Larval growth was inhibited on artificial diets containing 1 mumol g-1 diet of the glycoalkaloids solamargine, solasonine and tomatine, whereas the corresponding aglycones solasodine and tomatidine, and also tomatidenol, were inactive. The inhibitory effect of solamargine and tomatine, but not of solasonine, was completely abolished by addition of 1 mumol g-1 diet cholesterol and/or sitosterol. Nonetheless, synthetic cholesteryl tomatide displayed significant activity at 2 mumol g-1 diet. Parallel studies with the tobacco hornworm, Manduca sexta, showed marked inhibitory activity of tomatine at a dietary concentration of 1 mumol g-1, whereas the other compounds did not affect sterol metabolism or larval development. An appraisal of the factors influencing the mode of action of the active steroidal glycoalkaloids is attempted.