This study aims to investigate the chemical constituents of Rhododendron anthopogonoides Maxim. and their anti-inflammatory activity. Through the in vitro screening of cyclooxygenase-2 (COX-2) inhibition model identified the ethyl acetate extract fraction of the 95% ethanol extract of its stem and leaf was the anti-inflammatory active fraction. The anti-inflammatory active fraction was isolated and purified using silica gel column chromatography, Sephadex LH-20 gel column chromatography, and semi-preparative high-performance liquid chromatography (HPLC), followed by structural elucidation via nuclear magnetic resonance (¹H NMR, ¹³C NMR) spectroscopy. A total of 11 compounds were successfully isolated and identified, including 4-hydroxy-3-methoxyphenethylamine (1), p-hydroxybenzoic acid (2), vanillic acid (3), hydroquinone (4), 7-hydroxycoumarin (5), 2,4,6-trihydroxyacetophenone (6), orcinol (7), pubinernoid A (8), istanbulin B (9), pinobanksin (10), and rhododendrol (11). Compounds 1, and 7-10 were isolated from R. anthopogonoides for the first time, and compounds 1, 8-10 represent novel findings within the Rhododendron species. Further COX-2 inhibition evaluation demonstrated that compounds 1, 9, and 10 exhibited COX-2 inhibitory activity, with IC₅₀ values of 46.69 ± 4.16, 63.49 ± 0.27, and 62.70 ± 5.01 μmol/L, respectively.

Rhododendron anthopogonoides Maxim.; chemical constituents, pubinernoid A, istanbulin B, pinobanksin, COX-2 inhibitory activity