Non-Enzymatic and Enzymatic Antioxidant Responses of Hypericum perforatum L. Hairy Roots upon Photooxidative Stress

The aim of this study was to evaluate the non-enzymatic and enzymatic antioxidant response of fifteen Hypericum perforatum L. dark-grown (HR1 A-HR1 O) and photoperiod-exposed (HR2 A-HR2 O) hairy root clones. Dark-grown HR1 clones were characterized with high biomass accumulation and up-regulated phenylpropanoid metabolism through phenylalanine ammonia lyase (PAL)-mediated production of flavonoids, flavan-3-ols and anthocyanins. These groups of phenolics showed superior hydrogen-donating capability and significantly contributed to the antioxidant capacity of dark-grown HR1 clones. Photoperiod-exposed HR2 clones showed green coloration with shoot regenerative potential and reduced biomass accumulation. Photoperiod exposition improved the production of hypericins, as well as ferrous chelating properties and lipid peroxidation inhibition activity in HR2 cultures. Furthermore, HR2 clones were represented with enhanced activity of antioxidant enzymes (guaiacol peroxidase, catalase and superoxide dismutase) that resulted in suppression of oxidative stress markers (hydrogen peroxide, superoxide anion and malondialdehyde). These observations revealed the involvement of an efficient antioxidant defense system in the adaptive response of HR to photooxidative stress. Altogether, photoperiod-exposed H. perforatum HR2 clones were considered as a promising alternative for further scale-up production of naphthodianthrones that could be used in the pharmaceutical industry.