Isolation and Identification of Plant-Growth Inhibitory Constituents from Polygonum chinense Linn and Evaluation of Their Bioherbicidal Potential

Abstract

Polygonum chinense Linn. is a medicinal and invasive plant that belongs to the family Polygonaceae. The pharmacological activities and phytochemical constituents of Polygonum chinense are well reported, but the allelopathic effects and potent allelopathic substances of P. chinense remain to be investigated. Hence, this experiment was conducted to separate and characterize potentially allelopathic substances from an extract of the Polygonum chinense plant. The Polygonum chinense plant extracts highly suppressed the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crusgalli (L.) P. Beauv.), and timothy grass (Phleum pratense L.) seedlings in a species- and concentration-dependent way. Two active substances were separated using a series of purification procedures and determined through spectral analysis as (-)-3-hydroxy-β-ionone and (-)-3-hydroxy-7,8-dihydro-β-ionone. These two compounds significantly suppressed the seedling growth of Lepidium sativum (cress) at concentrations of 0.01 and 1 mM, respectively. The extract concentrations necessary for 50% growth inhibition (I₅₀ values) of the cress hypocotyls and roots were 0.05 and 0.07 mM for (-)-3-hydroxy-β-ionone, respectively, and 0.42 and 1.29 mM for (-)-3-hydroxy-7,8-β-ionone, respectively. These findings suggest that these two compounds are in charge of the inhibitory effects of the Polygonum chinense extract and may serve as weed control agents.

Keywords: (−)-3-hydroxy-7,8-β-ionone; (−)-3-hydroxy-β-ionone; Polygonum chinense; allelopathic substances.

Figure 1

Effect of Polygonum chinense plant extracts treated with different concentrations of 0.001, 0.003, 0.01, 0.03, 0.1, and 0.3 mg D.W. equivalent extract/mL (D.W.: dry weight) on the hypocotyls/coleoptiles and the root length of four test plant species. The means ± SE from six replications with 10 seedlings per replication (n = 60) for each determination are shown. *** represents a statistically significant difference between the control and the treatment: p < 0.001 (post hoc Tukey’s test).

Figure 2

Effect of Polygonum chinense plant extracts on the hypocotyls/coleoptiles and root length of four test plant species at different extract concentrations after 48 h of treatment. (D.W.: dry weight).

Figure 3

The chemical structures of the characterized allelopathic substances from Polygonum chinense extracts of Compound 1, (−)-3-hydroxy-β-ionone (A) and Compound 2, (−)-3-hydroxy-7,8-dihydro-β-ionone (B).

Figure 4

(A) Effects of (−)-3-hydroxy-β-ionone on the seedling growth of cress (Lepidium sativum) and (B) I₅₀ values. The means ± SE from three replications with 10 seedlings per replication (n = 30) for each determination are shown. *, and *** represent statistically significant differences between the control and the treatment: p < 0.05, p < 0.001 (post hoc Tukey’s test).

Figure 5

(A) Effects of (−)-3-hydroxy-7,8-dihydro-β-ionone on the seedling growth of cress (Lepidium sativum) and (B) I₅₀ values. The means ± SE from 3 replications with 10 seedlings per replication (n = 30) for each determination are shown. *, **, and *** represent a significant difference between the control and the treatment: p < 0.05, p < 0.01, p < 0.001 (post hoc Tukey’s test).