Correlation of different spectral lights with biomass accumulation and production of antioxidant secondary metabolites in callus cultures of medicinally important Prunella vulgaris L.

• Green light enhanced callus induction frequency in Prunella vulgaris.
• Yellow and violet lights improved fresh biomass during growth kinetics.
• Blue lights enhanced the production of phenolics and flavonoids content.
• Yellow light was found effective for total phenolics and flavonoids production.
• Yellow light also enhanced superoxide dismutase, peroxidase and protease activities.

Light is one of the key elicitors that directly fluctuates plant developmental processes and biosynthesis of secondary metabolites. In this study, the effects of various spectral lights on biomass accumulation and production of antioxidant secondary metabolites in callus cultures of Prunella vulgaris were investigated. Among different spectral lights, green light induced the maximum callogenic response (95%). Enhanced fresh biomass accumulation was observed in log phases on day-35, when callus cultures were exposed to yellow and violet lights. Yellow light induced maximum biomass accumulation (3.67 g/100 ml) from leaf explants as compared to control (1.27 g/100 ml). In contrast, violet lights enhanced biomass accumulation (3.49 g/100 ml) from petiole explant. Maximum total phenolics content (TPC; 23.9 mg/g-DW) and total flavonoids content (TFC; 1.65 mg/g-DW) were observed when cultures were grown under blue lights. In contrast, green and yellow lights enhanced total phenolics production (TPP; 112.52 g/100 ml) and total flavonoids production (TFP; 9.64 g/100 ml) as compared to control. The calli grown under green, red and blue lights enhanced DPPH-free radical scavenging activity (DFRSA; 91.3%, 93.1% and 93%) than control (56.44%) respectively. The DFRSA was correlated either with TPC and TFC or TPP and TFP. Furthermore, yellow lights enhanced superoxide dismutase (SOD), peroxidase (POD) and protease activities, however, the content of total protein (CTP) was higher in control cultures (186 μg BSAE/mg FW) as compared to spectral lights. These results suggest that the exposure of callus cultures to various spectral lights have shown a key role in biomass accumulation and production of antioxidant secondary metabolites.