Anti-complementary phenolic acids from Lonicera japonica

Abstract

To study the anti-complementary phenolic acids from Lonicera japonica. The anti-complementary activity-directed isolation was carried out with the hemolysis test as guide. All isolation was evaluated for their in vitro anti-complementary activities. The structures were identified by various spectroscopic data including ESI-MS, 1H-NMR, 13C-NMR data. Fourteen compounds were isolated from the EtOAc fraction of L. japonica extracts, including 8 phenolic acids: 5-O-caffeoylquinic acid (1), chlorogenic (2), 4-O-caffeoylquinic acid (3), 3,5-di-O-caffeoylquinic acid (4), 4,5-di-O-caffeoylquinic acid (5), 3,4-di-O-caffeoylquinic acid (6), caffeic acid (7) and methyl caffeate acid (8); 3 iridoids: secologanoside (9), sweroside (10) and secoxyloganin (11); and 3 flavonoids: luteolin (12), quercetin (13) and kaempferol (14). Compounds 1-9 and 11-14 showed anti-complementary activity in different extents and 3,5-di-O-caffeoylquinic acid (4) exhibited the most significant activity against the classical pathway. Compound 14 is obtained from this plant for the first time, phenolic acids are the main anti-complementary constituents of L. japonica and 3,5-di-O-caffeoylquinic acid(4) is a potential complement inhibitor with strong activity, which worthy to be studied further in the future.