Chemical analysis and biological activities of methanol extracts from Astragalus gombiformis Pomel (Fabaceae)

In the present study, wild Astragalus gombiformis Pomel extracts were tested for their biological activities and phenolic amounts. Antibacterial activity of this species against various bacteria was tested by the paper disk agar diffusion method and determination of the minimal inhibitor concentration. DPPH and ABTS assays were used to evaluate the antioxidant activity of methanol extracts. These extracts were also chemically investigated by spectrophotometric and HPLC analysis. For DPPH test, inhibitor concentrations 50% were 473.33±64.29 and 626.66±64.29µg/ml, respectively, for aerial part and roots methanol extracts. Ascorbic acid, used as positive control, showed an inhibitor concentration 50% of 7.36±0.70µg/ml. ABTS test showed that roots and aerial part extracts contain respectively, 47.13±0.05 and 79.81±1.31µmoles of Trolox equivalents per g of dry plant material weight. Chemical investigation showed that total polyphenols and flavonoids were three folds higher in aerial part methanolic extracts. The antioxidant potential seems to be correlated to the phenolic contents. Five among the tested extracts exhibited diameter of inhibition zone equal or above 12mm and with a minimal inhibitor concentration ranging between 233 and 1250µg/ml. However, no insecticidal effect of aerial part extracts was shown against Culex pipiens. It appears that both roots and aerial part of A. gombiformis extracts possess antioxidant and antibacterial effects and should be more studied for identification of active compounds.

Keywords: Astragalus gombiformis, Antibacterial, insecticidal, Antioxidant, phenolic amounts