Production of Phenylpropanoids, Naphthodianthrones and Antioxidant Status of Hypericum perforatum L. Transgenic Shoots

Abstract

Fifteen transgenic shoot clones (TS A-TS O) regenerated from Hypericum perforatum hairy roots were evaluated for growth characteristics, phenylpropanoid, and naphthodianthrone production, as well as non-enzymatic and enzymatic antioxidant status. Transgenic shoots displayed higher biomass production and non-altered phenotypes compared to control shoots. Phenylpropanoid production in TS was not related to phenylalanine ammonia lyase activity indicating that alternative enzymes could be involved in the regulation of phenylpropanoid/flavonoid biosynthesis. The positive correlation between phenylpropanoids (phenolic acids, flavonoids, flavan-3-ols, tannins) and non-enzymatic antioxidant assays suggested that these compounds are the main contributors to the redox state and radical scavenging properties of TS clones. More importantly, enhanced naphthodianthrone production (hypericin, pseudohypericin and protopseudohypericin) in TS was associated with the number of leaf dark glands. Concerning the enzymatic antioxidant status of TS, guaiacol peroxidase was shown as the main enzyme that turns down H2O2 levels, while the upregulation of superoxide dismutase coincided with decreased O2•− production. The efficiency of antioxidant enzymes for O2•− and H2O2 neutralization decreased the level of MDA and consequently delayed lipid peroxidation in TS clones. Altogether, H. perforatum transgenic shoots could be proposed as a prospective biotechnological system for scale-up production of naphthodianthrones and phenylpropanoids with antioxidant properties.