Elicitation and phenylalanine precursor feeding based modulation of in vitro anthocyanin production, enzyme activity and gene expression in an Indian ginseng congener- Panax sikkimensis Ban

Anthocyanins are colourful plant pigments belonging to the flavonoid group of plant natural products. Considered as potential dietary nutraceuticals, they are potent anti-oxidants imparting numerous health benefits. In the present study, an anthocyanin rich cell suspension line of an important ginseng congener from India, Panax sikkimensis Ban, was subjected to abiotic elicitation (Cobalt nitrate, Nickel sulphate, Lactalbumin hydrolysate, Casein hydrolysate) with the aim to enhance in vitro productivity of this desirable metabolite. Use of Nickel sulphate at 20 mu M and Lactalbumin hydrolysate at 150 mg/L for 3 weeks led to a 1.83 and 1.64 folds enhancement in anthocyanin yield as compared with control cultures. None of the treatments however could significantly enhance cell biomass accumulation. In order to further increase the anthocyanin productivity, a singular phenylalanine precursor feed (at two concentrations i.e 30 and 60 mu M) was co-administered along with Nickel sulphate and Lactalbumin hydrolyasate elicitation. Interestingly, phenylalanine supplementation with nickel sulphate, failed to further enhance anthocyanin production at either of the concentrations. However, addition of 30 mu M phenylalanine along with Lactalbumin hydrolysate at 150 mg/L led to a 2.03 folds and 3.5 folds enhancement in anthocyanin productivity when compared with cultures treated only with Lactalbumin hydrolysate and control cultures respectively. This treatment was also observed to positively upregulate enzyme activity and gene expression of two important anthocyanin biosynthetic pathway genes i.e PAL (phenylalanine ammonia lyase) and/or UFGT (UDP-glucose: flavonoid 3-O-glycosyltransferase). Since the inherent content of the immunomodulatory, anti-ageing and rejuvenating ginseng metabolites namely ginsenosides, were not significantly affected by these treatments, this particular ginseng cell line is of potential nutraceutical importance due to presence of both ginsenosides and anthocyanins.