Chemical constituents of Rumex dentatus L. and their antimicrobial and anti-inflammatory activities

Antimicrobial bioactivity-guided isolation of the root extract of Rumex dentatus L. resulted in the characterization of nineteen natural products, including three undescribed compounds (rumexs A−C). Rumexs A and B are rare anthraquinone-anthrone dimers consisting of an emodin-10-C-glycoside linked via C-10 to C-7 of a chrysophanol moiety. They differed only in their configuration at C-10; their absolute configurations were determined by NOESY and ECD analysis. LC-HRMS analysis was performed to identify nineteen compounds. Anthraquinone derivatives such as anthraquinone aglycone, oxanthrone C-glycoside, anthraquinone O-glycoside and anthraquinone dimer were found to be the dominant components of R. dentatus. In addition, naphthol, naphthoquinone, chromone, flavonoid, isocoumarin, and lignanamide derivatives were also identified. Chrysophanol and emodin were the most abundant compounds in the crude ethanol extract; their contents were determined by HPLC to be 7.38 and 5.74 mg/g, respectively. The fractions and isolated compounds were tested for their inhibitory activity against Staphylococcus aureus, Candida albicans, and Escherichia coli. Most of them showed inhibitory activity against S. aureus, some fractions and 2-methoxy-6-acetyl-7-methyljuglone exhibited moderate inhibitory activity against C. albicans, and 2-methoxy-6-acetyl-7-methyljuglone had moderate inhibitory effects against E. coli. Emodin exhibited inhibitory activity against NO release in LPS-reduced RAW264.7 cells in a concentration-dependent manner.