Allelopathic effect of the ethanol extract and fractions of the aerial parts of Lippia alba (Verbenaceae)

Lippia alba, belonging to the Verbenaceae family, is one of the most commonly utilized medicinal plants in folk medicine. The allelopathic activity was assessed using seeds of Lactuca sativa (lettuce) and Allium cepa (onion) by assessing the growth of the radicle and hypocotyl. The tests showed allelopathic efficiency in inhibiting the growth of lettuce and onion seeds. The best results for allelopathic activity were presented by the dichloromethane (DCM) fraction of the fresh plant, which inhibited radicle (23.04–100% lettuce and 64.17–66.36% onion) and hypocotyl (16.77–100% lettuce and 65.10–69.43% onion) formation, and as well as the DCM fraction of the dry plant, which also inhibited radicle (30.74–82.83% lettuce and 63.50–93.67% onion) and hypocotyl (24.12–70% lettuce and 69.07–79.95% onion) formation. Based on these results, it was found that the aerial parts of L. alba are rich in bioactive substances, suggesting the possibility of using of L. alba as a natural herbicide.