Elite hairy roots of Ocimum basilicum as a new source of rosmarinic acid and antioxidants

This study reports Agrobacterium rhizogenes-mediated transformation of three cultivars of Ocimum basilicum for hairy root establishment, screening and selection for the production of rosmarinic acid and antioxidants. Hairy root development was found to be explant-specific and virulence-dependent. Distinct inter-cultivar morphological variability was found between the seven axenically developed hairy root lines and morphological traits were found to be correlated with the presence of aux2 genes, their expression and endogenous IAA content. Further inter-cultivar variability in the content of total phenolics, rosmarinic acid and caffeic acid was also found. Production of rosmarinic acid was found to be age-dependent and cultivar-specific. Chemiluminescence analysis showed the hairy roots to be rich in antioxidants and that rosmarinic acid was the major antioxidant molecule. The concentration of rosmarinic acid was found to be positively correlated with the total antioxidant potential of the hairy root extracts. On the basis of origin, morphology and metabolite content, three elite hairy root lines were selected that had significantly higher rosmarinic acid production, biomass and antioxidant potential than non-transformed roots. These new lines are rich reserves of both antioxidants and rosmarinic acid.