Micropropagation of Rehmannia glutinosa Libosch.: production of phenolics and flavonoids and evaluation of antioxidant activity

Rehmannia glutinosa Libosch., a valuable medicinal plant, was successfully propagated in vitro using shoot tip explants. Shoot multiplication was performed in glass tubes and in a nutrient sprinkle bioreactor. A mixture of 0.1 mg L-1 indole-3-acetic acid (IAA) and 1.0 mg L-1 of 6-benzylaminopurine in Murashige and Skoog (MS) agar-solidified medium proved the best combination for multiple shoot induction, yielding 8.2 shoots per explant after 4 weeks of culture in glass tubes. The number of shoots increased to 21 per explant when the same combination of growth regulators was used in a nutrient sprinkle bioreactor. The shoots rooted with a frequency of 93 % after 6 weeks of culture on MS agar medium supplemented with IAA (0.1 mg L-1) before being acclimatized in the greenhouse. The antioxidant activities of methanolic extracts from the leaves and roots of the in vitro-regenerated plants of R. glutinosa cultivated in the greenhouse were evaluated using four in vitro assays: scavenging of free radicals (DPPH and ABTS), transition metal reduction and total antioxidant activity phosphomolybdenum test. In all cases, the methanolic extract from leaves demonstrated better antioxidant activity than those taken from roots. A strong correlation was found between total phenolic and flavonoid content, and the antioxidant capacity of the studied extracts.