Phenolic Compounds from the Roots of Rhodiola crenulata and Their Antioxidant and Inducing IFN-γ Production Activities

In the present study, two new phenolic compounds 1 and 11, a pair of lignan isomers 12 and 13 with their absolute configurations established for the first time, were isolated from the ethanol extract of the roots of Rhodiola crenulata, together with 13 known phenolic compounds, and their structures were elucidated via NMR, HRESIMS, UV, IR and CD analyses. All the isolated compounds were evaluated for their in vitro antioxidant activities using the 2,2-diphenyl-1-picryhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. Ten of them exhibited significant antioxidant activities compared to ascorbic acid. Furthermore, the inducibilities of the isolated compounds to IFN-γ production were also assessed. Compounds 1, 8, 9, 12, 13, 14 and 15 could moderately stimulate IFN-γ expression.