Radical scavenging activity and cytotoxicity of active quinic acid derivatives from Scorzonera divaricata roots

Five new quinic acid derivatives and two known 3-O-feruloylquinic acids were isolated from the roots of Scorzonera divaricata Turcz. The new compounds were elucidated as (–)–1,4-di-O-feruloyl-3-O-dihydrocaffeoylquinic acid, (–)–1-O-feruloyl-4-O- dihydrocaffeoylquinic acid, (–)–3,5-di-O-feruloylquinic acid, (–)–1-O-feruloyl-3-O-dihydro- caffeoylquinic acid, and (–)–1-O-feruloyl-5-O-dihydrocaffeoylquinic acid based on extensive spectroscopic studies, including one- and two-dimensional NMR, HRESIMS, UV, and IR results. Five compounds were assessed for antioxidant activity by ABTS and DPPH radical-scavenging assays and for their cytotoxicity against HL-60 and Hep-G2 cell lines by the MTT assay. Three quinic acid derivatives exhibited strong antioxidant activity, with IC50 values of 3.95, 5.87, and 7.45 μg/mL against ABTS+ and 11.7, 13.6, and 50.1 μg/mL against DPPH. (–)–1,4-Di-O-feruloyl-3-O-dihydrocaffeoylquinic acid also exhibited moderate activity against Hep-G2 cell lines with an IC50 value of 14.6 μg/mL.