Secondary metabolites from Alphonsea tonkinensis A.DC. showing inhibition of nitric oxide production and cytotoxic activity

Abstract

Context: Bioactivities of Alphonsea tonkinensis A.DC have not been reported previously, while the knowledge about its chemical composition is limited. Aims: To investigate the phytochemical constituents and bioactivities of the stems and leaves of Alphonsea tonkinensis A.DC. Methods: Combination of various extraction, chromatographic methods and crystallization techniques were performed to obtain pure compounds. Chemical structures of isolated compounds were determined by spectroscopic analyses (1D and 2D NMR). The in vitro anti-inflammatory and cytotoxic activities of isolates were evaluated by a Griess assay and a sulforhodamine B assay. Results: A phytochemical study of the stems and leaves of Alphonsea tonkinensis A.DC. resulted in the isolation of liriodenine (1), N–trans-feruloyltyramin (2), corydaldine (3), 8-oxopseudopalmatine (4), 3-hydroxy-7,8-dehydro-β-ionone (5), pseudopalmatine (6), pseudocolumbamine (7), and stigmasterol (8). Compound 5 showed potent inhibitory activity for NO production with an IC50 value of 20.4 μM, which was comparable to that of positive control. Compound 4 and 5 displayed inhibitions against the HepG2, SK-LU-1 cancer cell lines with IC50 values ranging from 54.4 and 69.6 µM. Conclusions: Among eight compounds isolated from Alphonsea tonkinensis A.DC., compounds 3 and 5 were isolated from the genus Alphonsea for the first time. Compound 5 was stronger inhibitor of NO production than positive control L-NMMA. In addition, this is the first investigation showing the bioactivities of 5 and cytotoxicity against the HepG2, SK-LU-1 cancer cell lines of 4.

Keywords

• 3-hydroxy-7
• 8-dehydro-β-ionone
• alphonsea tonkinensis
• cytotoxicity
• nitric oxide inhibition