Compounds from the pods of Astragalus armatus with antioxidant, anticholinesterase, antibacterial and phagocytic activities.

CONTEXT: The phytochemical study and biological activities of Astragalus armatus Willd. subsp. numidicus (Fabaceae) pods, an endemic shrub of Maghreb, are reported.

OBJECTIVE

This study isolates the secondary metabolites and determines the bioactivities of Astragalus armatus pods.

MATERIALS AND

METHODS

The chloroform, ethyl acetate and n-butanol extracts of hydro-ethanolic extracts were studied. Antioxidant activity was investigated using DPPH and ABTS radical scavenging, CUPRAC and ferrous chelating assays at concentrations ranging from 3 to 200 μg/mL. Anticholinesterase activity was determined against acetylcholinesterase and butyrylcholinesterase enzymes at 50, 100 and 200 μg/mL. Antibacterial activity was performed according to minimum inhibitory concentration (MIC) method. Carbon clearance method in albino mice was used for the phagocytic activity at concentrations 50, 70 and 100 mg/kg body weight. Spectroscopic techniques were used to elucidate the compounds.

RESULTS

Ethyl acetate extract afforded a flavonoid (1) while the n-butanol extract gave four flavonoids (2-5), a cyclitol (6) and a cycloartane-type saponin (7). The ethyl acetate extract exhibited highest antioxidant activity in DPPH (IC50: 67.90 ± 0.57 μg/mL), ABTS (IC50: 11.30 ± 0.09 μg/mL) and CUPRAC (A0.50: 50.60 ± 0.9 μg/mL) assays. The chloroform extract exhibited the best antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, each with 80 μg/mL MIC values. The n-butanol extract enhanced phagocytic activity.

DISCUSSION AND

CONCLUSION

Isorhamnetin (1), isorhamnetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-galactopyranoside (2), isorhamnetin-3-O-β-d-apiofuranosyl-(1 → 2)-[α-l-rhamnopyranosyl-(1 → 6)]-β-d-galactopyranoside (3), kaempferol-3-O-(2,6-di-O-α-l-rhamnopyranosyl)-β-d-galactopyranoside (4), kaempferol-3-O-(2,6-di-O-α-l-rhamnopyranosyl)-β-d-glucopyranoside (5), pinitol (6) and cyclomacroside D (7) were isolated whereas 1, 2, 6 and 7 are reported for the first time from A. armatus.