Bioactive indole alkaloids from Croton echioides

Abstract

Bioguided fractionation of a hydroethanolic extract from the stem bark of Croton echioides Baill. led to isolation of the new indole alkaloid N-trans-feruloyl-3,5-dihydroxyindolin-2-one as a stereoisomeric mixture and the known alkaloids N-trans-p-coumaroyl-tryptamine, N-trans-p-coumaroyl-5-hydroxytryptamine, N-trans-4-methoxy-cinnamoyl-5-hydroxytryptamine, N-transferuloyl-5-hydroxytryptamine (moschamine), from the ethyl acetate fraction. The flavonoids 3-o-methyl kaempferol, 3-o-methyl quercetin, 3,7-di-o-methyl quercetin and 3,3′-di-o-methyl quercetin, together with the benzoic acid derivatives 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzoic acid were also isolated. Alkaloids and the flavonoids showed strong antioxidant properties in vitro radical scavenging assay (2,2-diphenyl-1-picrylhydrazyl, DPPH), with IC50 values ranging from 9.2 to 17.5 μmol L-1, lower than those of the positive control Trolox (IC50 = 17.9 μmol L-1). Alkaloids showed cytotoxic activity against the HCT-116 human cancer cell line, with IC50 values ranging from 86.8 to 210.7 μmol L-1. Compound N-trans-4-methoxy-cinnamoyl-5-hydroxytryptamine was the most active, with an IC50 value of 86.8 μmol L-1.