Four new monoterpene indole alkaloids (1-4) together with twelve known alkaloids (5-16) were isolated from the roots of Alstonia rupestris. Compound 1 was the first example of C2-symmetric heteroyohimbine-type indole alkaloid homodimer obtained from natural plant resource. Their structures were elucidated on the basis of spectroscopic data. The absolute configuration of 1 was determined by comparison of its calculated and experimental electronic circular dichroism (ECD) spectra. All compounds were evaluated for their anti-inflammatory activities by measuring their NO inhibitory effects in LPS-stimulated RAW 264.7 cells. Compound 2 showed strong NO inhibition with IC50 value of 4.2 ± 1.3 μM. Moreover, compound 2 could decrease the expressions of cyclooxygenase-2 (COX-2) and transforming growth factor beta-1 (TGF-β1).
Keywords: Alstonia rupestris; Anti-inflammatory activity; COX-2; Indole alkaloid; TGF-β1.
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