The allelochemicals of litchi leaf and its potential as natural herbicide in weed control

This study aimed to exploit the allelopathic potential of Litchi chinensis (Litchi) and its application as naturally occurring herbicide in the field. Aqueous leaf extracts of L. chinensis inhibited the radicle growth of test weeds. Allelopathic compounds presented in litchi leaves were identified as (-)-epicatechin, procyanidin A2, kaempferol-3-O-galactose and 4-hydroxybenzaldehyde using chromatography, mass analysis and NMR spectroscopic analysis. Field experiments in orchard and vegetable fields demonstrated that litchi leaf powder inhibited the growth of weeds including Bidens pilosa, Eleusine indica and Portulaca oleracea. Interestingly, the growth of weeds plant (Ipomoea sp.) in orchard and vegetable plant (Brassica oleracea var. alboglabra) in vegetable fields was enhanced, indicating the beneficial usage of litchi leaf in vegetable farms. Developing the natural herbicide to replace the traditional agrochemicals becomes an important subject because the use of synthetic agrochemicals has caused serious environment pollution due to their poor biodegradability. These results obtained from laboratory assays, greenhouse pots experiments and field trials concluded that the L. chinensis leaves exhibited potential as natural herbicides.