Isolation and Identification of Two Potent Phytotoxic Substances from Afzelia xylocarpa for Controlling Weeds

Abstract

Phytotoxic substances released from plants are considered eco-friendly alternatives for controlling weeds in agricultural production. In this study, the leaves of Afzelia xylocarpa (Kurz) Craib. were investigated for biological activity, and their active substances were determined. Extracts of A. xylocarpa leaf exhibited concentration-dependent phytotoxic activity against the seedling length of Lepidium sativum L., Medicago sativa L., Phleum pratense L., and Echinochloa crus-galli (L.) P. Beauv. Bioassay-guided fractionation of the A. xylocarpa leaf extracts led to isolating and identifying two compounds: vanillic acid and trans-ferulic acid. Both compounds were applied to four model plants using different concentrations. The results showed both compounds significantly inhibited the model plants’ seedling length in a species-dependent manner (p < 0.05). The phytotoxic effects of trans-ferulic acid (IC50 = 0.42 to 2.43 mM) on the model plants were much greater than that of vanillic acid (IC50 = 0.73 to 3.17 mM) and P. pratense was the most sensitive to both compounds. In addition, the application of an equimolar (0.3 mM) mixture of vanillic acid and trans-ferulic acid showed the synergistic effects of the phytotoxic activity against the root length of P. pratense and L. sativum. These results suggest that the leaves of A. xylocarpa and its phytotoxic compounds could be used as a natural source of herbicides.

Allelopathic Activity of a Novel Compound, 5,6-Dihydrogen-11α-O-acetyl-12β-O-tigloyl-17β-marsdenin, and a Known Steroidal Glycoside from the Leaves of Marsdenia tenacissima (Roxb.) Moon

“…In addition, the I 50 values of the shoot and root growth of the two test plants varied, indicating that the inhibitory activity of the M. tenacissima extracts was species-dependent (Table 1). Similar results of concentration-and species-dependent inhibitory activity for extracts of Garcinia xanthochymus, Nephrolepis cordifolia, Albizia richardiana, Clerodendrum indicum, and Afzelia xylocarpa have also been reported [31][32][33][34][35]. Thus, the growth inhibitory activity of the M. tenacissima leaf extracts against the tested plants suggests that its leaf extracts may contain allelopathic substances.…”

“…Clerodendrum indicum, and Afzelia xylocarpa have also been reported [31][32][33][34][35]. Thus, the growth inhibitory activity of the M. tenacissima leaf extracts against the tested plants suggests that its leaf extracts may contain allelopathic substances.…”

Secondary Metabolites and Their Applications

“…were investigated as a natural source of herbicides. Krumsri et al [12] have identified vanillic acid and trans ferulic acid as the major bioactive compounds, both being responsible for the phytotoxic activity of Afzelia xylocarpa. The concentration of those compounds and differences in the sensitivity of the plant models are key to their phytotoxic action.…”