Topical analgesic, anti-inflammatory and antioxidant properties of Oxybaphus nyctagineus: phytochemical characterization of active fractions.

ETHNOPHARMACOLOGICAL RELEVANCE: Oxybaphus nyctagineus (Michx.) Sweet has traditionally been used by several Native American tribes predominantly as a topical anti-inflammatory and analgesic agent. AIM OF THE STUDY: To evaluate the antioxidant, analgesic and anti-inflammatory activity of the extracts prepared from the aerial parts of Oxybaphus nyctagineus and to characterize the major chemical constituents of the bioactive extracts. MATERIALS AND METHODS: Crude polar and apolar extracts (PCE and ACE) of the herb of Oxybaphus nyctagineus were prepared and tested in the models of the CFA-induced hyperalgesia in rat knee and carrageenan-induced paw edema in rat. To identify the active compounds, subfractions were prepared by column chromatography and subjected in vitro assays, such as antioxidant assays (DPPH, peroxynitrite (ONOO-) scavenging), and the LPS-induced IL-1ß release test in human monocytes. Preparative HPLC was employed for the isolation of active substances, while phytochemical analysis was performed by mean of LC-MS/MS and NMR. RESULTS: The topically administered PCE and ACE of Oxybaphus nyctagineus demonstrated a significant analgesic and anti-inflammatory effect in the inflammation animal models. The subfraction A4 of ACE and the subfraction P5 of PCE considerably inhibited the LPS-induced IL-1ß release in human monocytes, while the strongest activity was localized in the subfraction P5 in the antioxidant assays. The HPLC-MS/MS and NMR analysis revealed that 6-methoxyflavonol diglycosides, namely patuletin-3-O-robinobioside (1), 6-methoxykaempferol-3-O-robinobioside (2), spinacetin-3-O-robinobioside (3), and hydroxy-polyenoic fatty acids, namely corchorifatty acid B (4), 9-hydroxy-10E,12Z,15Z-octadecatrienoic acid (9-HOT acid) (5), and 9-hydroxy-10E,12Z-octadecadienoic acid (9-HOD acid) (6) were present in PCE, and in ACE as major compounds. CONCLUSION: The results of this study established a pharmacological evidence for the traditional use of Oxybaphus nyctagineus as an anti-inflammatory agent used topically, and provided data on its phytochemical composition for the first time.