Bioactive Secondary Metabolites from the Aerial Parts of Buddleja macrostachya

Abstract

A new iridoid glycoside, buddlemacroside A (1) and 15 known compounds, including 6-α-L-(4″-O-trans-p-coumaroyl)rhamnopyranosylcatalpol (2), 6-α-L-(2″-caffeoyl)rhamnopyranosylcatalpol (3), salidroside (4), echipuroside A (5), darendoside A (6), decaffeoylacteoside (7), acteoside (8), martynoside (9), 8-hydroxylinalool 3-O-β-D-glucopyranoside (10), 9-O-α-L-rhamnopyranosyl-4-hydroxy-cinnamic acid (11), apigenin (12), acacetin-7-O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside (13), mimengoside C (14), buddlejasaponin Ia (15), and buddejasaponin I (16) were isolated from a methanol extract of the aerial parts of Buddleja macrostachya Benth. Their chemical structures were elucidated by extensive spectroscopic analyses, including MS and NMR spectra as well as by comparison with the data reported in the literature. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test showed that compounds 3 and 7-9 possess significant scavenging capacity, with SC₅₀ values ranging from 6.9-19.6 μM. Compound 8 was shown to have potent inhibitory effect against the release of malondialdehyde (MDA) - the major product of the cellular lipid peroxidation, with IC₅₀ value of 2.3 μM. Compounds 12 and 16 significantly inhibited nitrite production in LPS-stimulated BV2 microglia, with IC₅₀ values of 14.2 and 11.4 μM, respectively. Furthermore, compound 16 showed cytotoxicity toward three human cancer cell lines, including SK-LU-1, MCF7, HepG2, with IC₅₀ values in the range of 6.5-8.0 μM.