Ethnopharmacological relevance: Seventeen plants used in Vietnamese traditional medicine for the\ntreatment of inflammatory disorders were screened for NF-?B inhibitory activity. Oroxylum indicum,\nwhich exhibited activity, was investigated in detail.\nMaterials and methods: Forty plant extracts from 17 species were prepared by maceration using\ndichloromethane and methanol and were tested (10 mg/mL) to evaluate their ability to inhibit NF-?B\nactivation using TNF-?-stimulated HEK-293 cells stably transfected with a NF-?B-driven luciferase\nreporter. The active extract of Oroxylum indicum was subsequently fractionated by different chromatographic\ntechniques. After isolation, all single compounds were identified by spectroscopic methods and\nassessed for NF-?B inhibitory effects.\nResults: The dichloromethane extracts obtained from Chromolaena odorata leaves and the stem bark of\nOroxylum indicum showed distinct inhibitory effects on NF-?B activation at a concentration of 10 mg/mL.\nThe active extract of Oroxylum indicum was subjected to further phytochemical studies resulting in\nidentification of four flavonoid aglyca and six flavonoid glycosides. Pharmacological evaluation of the\nobtained compounds identified oroxylin A as the most active substance (IC50Ã?¼3.9 mM, 95% CI: 3.5ââ?¬â??\n4.4 mM), while chrysin and hispidulin showed lower activity with IC50Ã?¼7.2 mM (95% CI: 6.0ââ?¬â??8.8 mM) and\n9.0 mM (95% CI: 7.9ââ?¬â??10.2 mM), respectively. Interestingly, in this study the activity of baicalein\n(IC50Ã?¼28.1 mM, 95% CI: 24.6ââ?¬â??32.0 mM) was weak. The isolated glycosides showed no inhibitory activity\nwhen tested at a concentration of 30 mM. Quantification of the four active flavonoids in extracts and plant\nmaterials suggested that oroxylin A contributes to the NF-?B inhibitory activity of the stem barks of\nOroxylum indicum to a greater extent than baicalein which was thought to be responsible for the antiinflammatory\nactivity of this plant.\nConclusions: The screening presented in this study identified the dichloromethane extracts of Chromolaena\nodorata and Oroxylum indicum as promising sources for NF-?B inhibitors. Hispidulin, baicalein,\nchrysin and oroxylin A, isolated from Oroxylum indicum, were identified as inhibitors of NF- ?B activation.
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