Potential of trans-p-coumaric acid released from Rottboellia cochinchinensis for weed control in vegetable fields

We characterized the phytotoxic allelochemicals in itchgrass (Rottboellia cochinchinensis) and assessed their phytotoxic effects on early seedling growth of Ageratum conyzoides L., Bidens pilosa L. var. radiata Sch. Biq., Echinochloa crus-galli (L.) P. Beauv. and Lactuca saliva L. The aqueous methanol extract of itchgrass inhibited the growth of A. conyzoides, B. pilosa, E. crus-galli and L. sativa. Aqueous methanol extract at 1.50 mg/mL inhibited shoot growth of L. saliva by 65.8 % than control. These results indicated that itchgrass contains growth inhibitory substances (allelochemicals), which were detrimental to target plant species. Based on electrospray ionization-mass spectrometry (ESI-MS) data and H-1 and C-13 nuclear magnetic resonance (NMR) spectra, the allelochemical isolated from the aqueous methanol extract was identified as trans-p-coumaric acid. Both isolated and the commercial trans-p-coumaric acids inhibited the growth of A. conyzoides, B. pilosa, E. crus-galli and L. saliva at > 0.08 mg/mL concentration than control, except the root growth of L. sativa. Considering the endogenous level and the inhibitory effects the trans-p-coumaric acid may be responsible for the growth inhibitory effects, of itchgrass and may play an active role in the allelopathy of itchgrass for weed control.