Glutathione elicits enhanced biosynthesis of bonducellin, a homoisoflavonoid, in Caesalpinia bonducella leaf callus

Caesalpinia bonduc (L.) Roxb. [Family: Fabaceae (Caesalpiniaceae)], a traditional medicinal plant, has profound therapeutic value and is recently used for the treatment of polycystic ovary syndrome in India. Its seeds and kernels rich in bioactive homoisoflavonoids like bonducellin are reported to possess antioxidant, anti-bacterial, anti-inflammatory, anticancer, anti-estrogenic, and anti-androgenic properties. Considering such therapeutic significance, in vitro propagation of C. bonducella warrants action for enhanced production of secondary metabolites as harvesting seeds for long might pose an extinction threat. The present study aimed to introduce and optimize a protocol for inducing leaf callus and eliciting enriched synthesis of bonducellin compound. Of different combinations of plant growth regulators (PGRs), 2,4-dichloro phenoxy acetic acid (2,4-D) and 6-benzyl amino purine (BAP) at a low concentration of 0.5 and 0.2 mg/L, respectively, induced profuse biomass (2.12 g FW at 20 dpi) in MS medium with 98.6% frequency. Abiotic elicitors, glutathione (GSH), and salicylic acid (SA) at 10 µM and 20 µM concentrations were amended to the above callus initiation medium. The content of bonducellin, analyzed using HPLC with the chemically synthesized standard, increased significantly (5.8 mg/g DW) in the callus elicited with 20 µM glutathione for 15 days which is 1.48-fold higher as compared to that in the untreated control (3.9 mg/g DW). However, elicitation with 20 µM salicylic acid resulted in a lower level of bonducellin (2.38 mg/g DW). The present finding provides an insight into the potential of GSH as a prospective elicitor of homoisoflavonoid, bonducellin, in C. bonducella leaf callus and opens avenues toward fulfilling the rising commercial requirements of novel anti-PCOS and metabolic drugs in the future.