Rhododendron luteum Sweet Flower Supercritical CO2 Extracts: Terpenes Composition, Pro-Inflammatory Enzymes Inhibition and Antioxidant Activity

Terpenes are plant secondary metabolites known for their anti-inflammatory and antioxidant activities. According to ethnobotanical knowledge, <i>Rhododendron luteum</i> Sweet was used in traditional medicine against inflammation. The present study was conducted to determine the triterpene profile and antioxidant and anti-inflammatory activity of supercritical CO₂ (SC-CO₂) extracts of <i>Rhododendron luteum</i> Sweet flower (RLF). An LC-APCI-MS/MS analysis showed the presence of eight pentacyclic triterpenes and one phytosterol in the extracts obtained with pure CO₂ as well as CO₂ with the addition of aqueous ethanol as a co-solvent. Among the compounds detected, oleanolic/ursolic acid, β-sitosterol and 3<i>β</i>-taraxerol were the most abundant. The extract obtained with pure SC-CO₂ was additionally subjected to HS-SPME-GC-FID-MS, which revealed more than 100 volatiles, mainly eugenol, <i>β</i>-phenylethanol, dodecane, <i>β</i>-caryophyllene, estragole and (<i>Z</i>)- and (<i>E</i>)-cinnamyl alcohol, followed by <i>δ</i>-cadinene. The extracts demonstrated significant hyaluronidase inhibition and exhibited varying modes of lipoxygenase and xanthine oxidase inhibitory activities. The studies of RLF have shown that their SC-CO₂ extracts can be a rich source of triterpenes with anti-inflammatory potential.