Chemical constituents and their biological activities of Gymnema inodorum Decne. and Moringa oleifera Lam

Abstract

The CH [subscript 2]Cl[subscript 2] and n-BuOH crude extracts of G. inodorum and those of the roots of M. oleifera revealed a promising antioxidant and α-amylase inhibitor activities. Chromatographic separation of the CH[subscript 2]Cl[subscript 2] extract of G. inodorum led to the isolation of three known substances: a long chain alcohol, a long chain ketone and a mixture of steroids containing stigmasterol as a major component. While two known saponins, (3β,4α,16β)-16,23,28-trihydroxyolean-12-en-3-yl-β-D-glucopyranosiduroic acid and (3β,16β,22α)-16,28-dihydroxyolean-12-en-3-yl-O-β-D-glucopyranosyl-β-D-glucopyranosiduroic acid were isolated from the n-BuOH crude extract. Four known substances: a long chain alcohol, a long chain ketone, a mixture of β-sitosterol, campesterol and stigmasterol along with a mixture of triglycerides as 1,3-dilinoleoyl-2-olein, 1,3-dioleoyl-2-linolein and 1,2,3-trilinolein were isolated from the CH [subscript 2]Cl[subscript 2] crude extract of the roots of M. oleifera. In addition, five known compounds were isolated and identified as linoleic acid, isothiocyanatomethylbenzene, 1,2,3-triolein, benzamide, β-sitosteryl linoleate and β-sitosterol-3-O-β-D-glucopyranoside. All isolated substances were assayed for antioxidant, the inhibition of cholinesterase activity and α-amylase inhibitor. Only (3β,16β,22α)-16,28-dihydroxyolean-12-en-3-yl-O-β-D-glucopyranosyl-β-D-glucopyranosiduroic acid was active for radical scavenging effect on DPPH radical. The α-amylase inhibition of (3β,16β,22α)-16,28-dihydroxyolean-12-en-3-yl-O-β-D-glucopyranosyl-β-D-glucopyranosiduroic acid (38.59%) was better than that of (3β,4α,16β)-16,23,28-trihydroxyolean-12-en-3-yl-β-D-glucopyranosiduroic acid (9.80%). Moreover, benzamide isolated from the CH2Cl2 crude extract of M. oleifera roots showed the highest scavenging activity on DPPH, while β-sitosterol-3-O-β-D-glucopyranoside was found as a good inhibitor for α-amylase inhibition with IC50 of 0.326 mM. The synthetic derivatives of certain carboxamides and esters were also prepared to test for scavenging effects on DPPH radical. N-(2-hydroxylphenyl)-5-(3,4-methylenedioxyphenyl)-2E,4E-pentadieneyl amide showed highly active toward radical scavenging effect on DPPH radical with IC50 of 0.470 mM and ABTS value being similar to that of trolox revealing good potent for antioxidant activity.