Light-mediated biosynthesis of phenylpropanoid metabolites and antioxidant potential in callus cultures of purple basil ( Ocimum basilicum L. var purpurascens )

Ocimum basilicum L. var purpurascens (purple basil) contains medicinally valuable metabolites. Light greatly influences the physiological processes, including biomass accumulation and secondary metabolites production in medicinal plants. Herein, we investigated the influence of different spectral lights on the biosynthesis of phenylpropanoid metabolites in purple basil callus cultures. Growth kinetics was østudied for a total of 49 days, with 7 days of sampling time. Among the various treatments, blue light resulted in maximum biomass accumulation, total phenolic content (TPC), total flavonoid content (TFC) and antioxidant DPPH, FRAP and ABTS activities, as compared to controls. Moreover, blue light also encouraged higher superoxide dismutase activity while the red light was found effective for enhanced peroxidase activity. HPLC analysis revealed enhanced rosmarinic acid (87.62 mg/g DW) and anthocyanins (cyanidin: 0.15 mg/g DW and peonidin: 0.13 mg/g DW) contents under dark grown callus cultures which were almost 1.55, 1.25 and 1.18–fold greater than controls, respectively. Conversely, red light caused maximum production of cichoric acid (14.65 mg/g DW). Moreover, a positive correlation occurred among the accumulation of phenolic and flavonoids and antioxidant activities. These results suggest that light quality strongly influences medicinally valuable phenylpropanoid metabolites biosynthesis along with antioxidant potential in in vitro cultures of purple basil.