Natural and unnatural anthraquinones isolated from the ethanol extract of the roots of Knoxia valerianoides

Abstract

Eight new 9,10-anthraquinones (1–8) including three acetonide derivatives of 3-hydroxy-2-hydroxymethyl-9,10-anthraquinones (6–8) were isolated from an ethanol extract of the roots of Knoxia valerianoides. On the basis of chemical transformation reactions of the co-occurring 14 and 15 combined with HPLC–DAD–ESI–MS analysis of the extracts, the previously and newly isolated 2-methoxymethyl- and 2-ethoxymethyl-9,10-anthraquinones (4, 5, and 9–13), as well as the 3-hydroxy-2-hydroxymethyl-9,10-anthraquinone acetonide derivatives (6–8), were shown to be solvolytic artifacts. In the in vitro assays, compound 4 was active to protect hepatocyte (WB-F344) damage.

Keywords

• Knoxia valerianoides
• Rubiaceae
• Anthraquinone
• Solvolytic artifacts
• HPLC–DAD–ESI–MS analysis
• Hepatocyte (WB-F344) damage protection