Chemical Constituents from Coleus strobilifer and Their Xanthine Oxidase Inhibitory Activity

<i>Coleus strobilifer</i>, the dried rhizome and root of <i>Coleus strobilifer</i> (Roxb.) A.J. Paton, is widely used for dampness-detoxification and detumescence in Chinese folklore. This study marks the first comprehensive investigation into the chemical composition of the whole herb of <i>C. strobilifer</i>, leading to the isolation and identification of two new abietane diterpenes, 10<i>R</i>-carnosuain (<b>1</b>) and 10<i>R</i>-coleon U-3-one (<b>2</b>), along with 34 known compounds (<b>3</b>-<b>36</b>) isolated from <i>C. strobilifer</i> for the first time. Their structures were unambiguously elucidated by analyses of NMR, HRESIMS, IR, CD, and single-crystal X-ray diffraction data, and comparison with the literature. All the isolated compounds were screened for their xanthine oxidase (XO) inhibitory activity. Among them, apigenin (<b>8</b>), luteolin (<b>9</b>), and esculetin (<b>29</b>) showed moderate XO inhibitory activity with IC₅₀ values of 0.034 ± 0.004, 0.067 ± 0.005, and 0.284 ± 0.01 mM, respectively.