Sucrose induced osmotic stress and photoperiod regimes enhanced the biomass and production of antioxidant secondary metabolites in shake-flask suspension cultures of Prunella vulgaris L.

Prunella vulgaris L. is a very important species with worldwide traditional medicinal uses. Despite of its medicinal importance, there is lack of research efforts on cultivation and phytochemicals production of this plant. In the present study, an effort has been made to optimize various culture conditions for establishment of cell suspension culture and production of desired secondary metabolites. Initially, callus was induced from petiole explants on Murashige and Skoog medium supplemented with 2.0 mg/l naphthalene acetic acid (NAA) in dark. For establishment of suspension culture, friable calli were shifted to liquid medium fortified with 2.0 mg/l NAA. The differential effects of sucrose (5–50 g/l), pH (5–6) and different photoperiod regimes on suspension biomass, secondary metabolites accumulation and antioxidant activities were investigated. Maximum levels of biomass, phenolics, flavonoids, protein content and antioxidant activities were displayed by cultures treated with 20–25 g/l of sucrose. Similarly, a lower pH of 5.3 resulted in enhanced biomass, phenolics, flavonoids, protein content and antioxidant activities. Furthermore, the cultures grown under 12D/18L, 14D/16L and 16D/14L photoperiods exhibited higher levels of biomass and secondary metabolites, compared to control (16L/8D). These investigations conclude that sucrose, different pH levels and photoperiod regimes modulate cell growth and the production of bioactive compounds in cell suspension cultures of P. vulgaris.