Secondary Metabolite Production through Elicitation: Biotic, Abiotic, MeJA, PGRs and Stress Signaling in Improving Compounds in Select Medicinal Plants

Abstract

Plants in addition to primary metabolites produce secondary metabolites which are of immense pharmaceutical importance and other industrial uses. Secondary metabolites are produced due to the stress experienced by plants in response to external triggers/agents like elicitors. Elicitation involves two types of elicitors namely biotic and abiotic. Elicitors have a vital role in plant tissue culture as these improve secondary metabolite content in cultures. Other culture conditions including volume and types of medium, duration, etc., also affect the yield of alkaloids. Extensive research has been carried out for the enhanced level of alkaloids in in vitro cultured plants. Various common elicitors used in media are methyl jasmonate (MeJA), yeast extract (YE), fungal extract, ions from various salts like CdCl2, heavy metal ions, and ionic, nonionic radiations, etc. The fungal cell wall components oligosaccharides and peptides have also been used as elicitors for the induction/enhancement of secondary metabolites in plant cell/organ cultures. The influence of sample representation of biotic and abiotic elicitors, i.e., YE, Aspergillus flavus, MeJA, CdCl2 , CaCl2, has been discussed taking a few medicinals and oil yielding plants from authors’ laboratory. A direct link of stress with elicitors including plant growth regulators (PGRs) has been established showing over accumulation of proline, protein, SOD, APX and other antioxidant enzyme activity with increased levels of elicitation. Increasing demand forces researchers to conduct further investigation in this area for the production of phyto-compounds and even for viable commercial exploitation.