Antitrypanosomal and opioid receptor activity of Mussaenda Luteola's secondary metabolites

Five new secondary metabolites; heinsiagenin A-3-O-α-L-rhamnopyranosyl(1→2)-O-β-D-glucopyranosyl (1→4)-O-β-D-glucopyranoside (1), heinsiagenin A-3-O-[α-L-rhamnopyranosyl(1→2)-O-β-D-glucopyranosyl (1→2)]-O-β-D-glucopyranosyl (1→4)-O-β-D-glucopyranoside (2), N-(2S,3R,4R-3-methyl-4-pentanolid-2yl)-18-hydroxylansta-8(9), 22E,24E-trien-27-amide-3-O-[α-L-rhamnopyranosyl(1→2)-O-β-D-glucopyranosyl (1→2)]-O-β-D-glucopyranosyl (1→4)-O-β-D-glucopyranoside (3), iridoid glucoside; (5α, 9α)-8-epiloganin (4), and 6-oxy-10-methoxy strictosamine (5) were isolated from the aerial part of Mussaenda luteola (Rubiaceae) along with 5α-carboxystrictosidine (6), (7α)-morroniside, (7β) 7-O-methyl morroniside and apigenin 7-O-neohesperidoside. Compounds 1 and 2 showed good activity in Mu opioid receptor binding assay with 65.9 and 61% inhibition, respectively. Compounds 2 and 6 showed antitrypanosomal activity against Trypanosoma brucei with IC₅₀ and IC₉₀ values of 3.08 and 4.27 µg/mL, respectively for 2 and 7.90 and 9.56 µg/mL, respectively for 6 (using difluoromethylornithine as a positive control with IC₅₀ and IC₉₀ values of 3.586 and 8.089 µg/mL, respectively for 2 and 8.169 and 14.419 µg/mL, respectively for 6).