Multiple shoot cultures of two experimental lines of Withania somnifera plants (RS-Selection-1 and RS-Selection-2) were established using nodal segments as explants. The hormonal combinations of benzyl adenine and kinetin not only influenced their morphogenetic response but also differentially modulated the level of biogeneration of withanolide A in the in vitro shoots of the two lines. Interestingly, withanolide-A, that was hardly detectable in the aerial parts of field-grown Withania somnifera (explant source), accumulated considerably in the in vitro shoot cultures of the plant. The productivity of withanolide A in the cultures varied considerably (ca. 10-fold, 0.014 to 0.14 mg per gram fresh weight) with the change in the hormone composition of the culture media as well as genotype used as source of the explant. The shoot culture of RS-Selection-1 raised at 1.00 ppm of BAP and 0.50 ppm of kinetin displayed the highest concentration of withanolide A in the green shoots of 0.238 g per 100 g dry weight tissue. This was a more analytical concentration keeping in view the isolation yields so far reported from the dried roots of the field-grown plant (ca. 0.015 g per 100 g dry weight), even if isolation losses are considered during purification. The enhanced de novo biogenesis of withanolide A in shoot cultures was corroborated with radiolabel incorporation studies using [2-14C] acetate as a precursor. Production of withaferin A was also found in the in vitro shoot cultures. As this compound is a predominant withanolide of native shoots as well and has been already reported to be accumulated in in vitro shoot cultures, its biogeneration observed in these shoot cultures is not discussed in detail.

Monoamine oxidase inhibitors (MAOIs) are an important class of drugs prescribed for treatment of depression and other neurological disorders. Evidence has suggested that patients with atypical depression preferentially respond to natural product MAOIs. This review presents a comprehensive survey of the natural products, predominantly from plant sources, as potential new MAOI drug leads. The psychoactive properties of several traditionally used plants and herbal formulations were attributed to their MAOI constituents. MAO inhibitory constituents may also be responsible for neuroprotective effects of natural products. Different classes of MAOIs were identified from the natural product sources with non-selective as well as selective inhibition of MAO-A and -B. Selective reversible natural product MAOIs may be safer alternatives to the conventional MAOI drugs. Characterization of MAO inhibitory constituents of natural products traditionally used as psychoactive preparations or for treatment of neurological disorders may help in understanding the mechanism of action, optimization of these preparations for desired bioactive properties, and improvement of the therapeutic potential. Potential therapeutic application of natural product MAOIs for treatment of neuroblastoma is also discussed.