Isolation and identification of chemical constituents of the aerial parts of Astragalus complanatus and their antibacterial activities

For the comprehensive utilization of medicinal plant Astragalus complanatus, the chemical constituents of its the non-meidcinal parts and their antibacterial activities were investigated preliminarily. Seven compounds were isolated by using silica gel and LH-20 gel chromatography, and their antibacterial activities against 8 species of bacteria were evaulated. After spectrometric analysis, the obtained compounds were identified as β-sitosterol (1) , β-sitostenone (2) , lawsaritol A (3) , 8-epidioxy-5α,8α-ergosta-6,22E-dien-3β-ol (4) , 3′,7-dihydroxy-2′,4′-dimethoxyisoflavan (5) , D-1-O-methyl inositol (6) and complanatuside (7) . All of the above compounds were isolated from the aerial parts of A. complanatus for the first time. Compound 5 showed inhibition effect on Bacillus cereus, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Erwinia carotovora, Pseudomonas syringae pv. actinidiae and Ralstonia solanacearum, and the MIC values of compound 5 against three species of plant pathogenic bacteria, including P. syringae, R. solanacearum and E. carotovora, were 37.5, 18.8 and 75 μg/mL, respectively. To our best knowledge, this is the first report about the inhibition effect of 5 on plant pathogenic bacteria.