New triterpenic acids from Uncaria rhynchophylla: Chemistry, NO-inhibitory activity, and tandem mass spectrometric analysis

Five new oleanane and ursane type triterpenes, namely uncarinic acids F–J (1–5), together with six known triterpenic acids (6–11) were isolated from the stems and hooks of Uncaria rhynchophylla. Structure elucidation of 1–5 was based on the integrated analyses of high-resolution MS data, 1D (1H NMR, 13C NMR, DEPT) and 2D (HSQC, HMBC, ROESY) NMR spectra. Compounds 4, 10, and 11 exhibited weak inhibitory effects on LPS-induced NO production in RAW264.7 cells (with IC50 1.48, 7.01, and 1.89 μM, respectively) with dexamethasone (IC50 0.04 μM) and quercetin (IC50 0.86 μM) as the positive controls. 19-OH substituted oleanane triterpenic acids (1, 2, 5, 8) were prone to eliminate CH2O3, whereas those ursane-type encompassing 19-OH (3, 6, 7, 9, 4) were featured by preferred cleavage of H2O while performing the negative collision-induced MS/MS fragmentation on an LTQ/Orbitrap mass spectrometer.

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