Impacts of hormonal elicitors and photoperiod regimes on elicitation of bioactive secondary volatiles in cell cultures of Ajuga bracteosa.

Light is an important physical factor necessary for the growth, morphogenesis and production of bioactive compounds in plants. In this study, effects of different photoperiod regimes and hormonal elicitors were investigated on the accumulation of biomass, antioxidant potential and biosynthesis of secondary volatiles in the cell cultures of Ajuga bracteosa. Maximum accumulation of biomass (13.2 g/L) was recorded in cell cultures established at 1.0 mg/L benzylaminopurine (BA) in exposure to continuous dark. Biochemical assays showed that in the presence of 0.5 methyl jasmonate (Me-J), cell cultures grown under continuous dark had the higher activities of superoxide dismutase (SOD: 4.5 U/mg), peroxidase (POD: 3.1 U/mg), total phenolic content (TPC: 8.1 mg GAE/g of DW) and total flavonoid content (TFC: 5.2 mg QE/g of DW) respectively. Nonetheless, the free radical scavenging activity (FRSA) was found correlated with the phenyl ammonia lyase (PAL) activity in the dark grown cell cultures. Analysis through gas chromatography-mass spectrometry (GC-MS) showed, biosynthesis of 29 compounds in the in vitro raised cell cultures. The major identified compounds consisted of monoterpene hydrocarbons such as β-pinene (2.1-9.5%), β-ocimene (1.4-8.3%), 1-terpinene-4-ol (5.8-9.6%), caryophyllene (1.3-6.2%), β-farnesene (0.82-7.8), oxygenated monoterpenes including myrtenal (2.2-8.4%), citronellyl acetate (2.1-7.3%) and sesquiterpenes such as caryophyllene oxide (1.5-5.5) and β-elemene (2.2-8.8%). This protocol has the potential for commercial production of important secondary volatiles.