Allelopathic potential and identification of two allelopathic substances in Eleocharis atropurpurea

Eleocharis atropurpurea is an annual weed and distributed widely in pantropical and subtropical regions. Yet, there have been no studies on the allelopathy of E. atropurpurea. Therefore, we investigated the allelopathic potential of E. atropurpurea to identify allelopathic substances from it. The aqueous methanolic extracts of E. atropurpurea showed an inhibitory effect on the seedling growth of lettuce, rapeseed, barnyard grass and foxtail fescue. Inhibition was species- and concentration-dependent. Two substances, syringaldehyde and acetosyringone, were isolated by using chromatography and using spectroscopy their structures were determined. Syringaldehyde and acetosyringone inhibited the shoot and root growth of cress and barnyard grass at concentrations greater than 3.0 mM except shoot growth of barnyard grass by acetosyringone. Concentration and seedling growth of cress and barnyard grass displayed a negative correlation. The I ₅₀ values of syringaldehyde and acetosyringone for the shoot and root growth of cress were 1.67 and 1.61 mM, and 1.49, and 1.29 mM, respectively, whereas for the shoot and root growth of barnyard grass the values were 4.09 and 2.41 mM, and 4.54 and 1.92 mM, respectively. Therefore, it is suggested that these compounds may contribute to the inhibitory effects of E. atropurpurea.