Stability of phenolic acids and the effect on weed control activity

Abstract

Phenolic acid is a very important class of allelochemicals with allelopathic weed control activity. In this study, three benzoic acid derivatives (syringic, 4-hydroxybenzoic, and vanillic acids), three cinnamic acid derivatives (cinnamic, 4-hydroxycinnamic, and ferulic acids) were tested, and high-performance liquid chromatography was used to conduct a dynamic analysis on the changes in the concentration of phenolic acids in a bioassay based on the initial concentration and test time. The results showed that the concentration of individual phenolic acids and a solution of mixed phenolic acids decreased to a certain extent irrespective of environment, i.e., bioassay (4-7 days) or a ricegrowing environment, and a significant decrease in concentration was measured after 48 h. Based on the above results, the laboratory bioassay was conducted using a fresh solution of phenolic acids every 48 h. The results showed that the instability of phenolic acid could affect its weed control activity, and this effect was more significant for high concentrations of phenolic acids. On the other hand, changing the solution did not have a significant impact on the weed control activity of phenolic acids in the natural environment (pH 6.50), in which allelopathic rice release phenolic acids. These results reveal the instability of phenolic acids could significantly reduce the inhibition rate on the growth index for receptor plants in an indoor bioassay.

Phytotoxic effects of volatile and water soluble chemicals of Artemisia herba-alba

“…In addition, it could be possible that there were very small amounts of certain compounds belonging to other chemical classes (e.g., terpenes) in the aqueous extract (Weidenhamer et al, 1993), which might have also inhibitory effects. On the other hand, pure compounds in the mixture probably degrade faster than they do in the aqueous extract (Li et al, 2015).…”

The allelopathic properties of decomposing buckwheat residues are not directly related to phenolic compounds in soil

“…The content of phenols in the soil is known to decrease due to their instability caused by chemical processes in the soil and metabolic processes in microorganisms (Zhang et al 2010, Li et al 2015. Decaying plant residues can regulate the soil microbial community as well as chemical and physical properties of the soil, which may indirectly affect the growth of weeds (Javaid 2007).…”

“…After measuring the shoot and main root length in the 7-day old barnyardgrass seedlings, they were then placed in beakers containing 200 mL of solution of the tested compound or water (control). Due to the instability of phenolic compounds in water solution (Roger et al 1999, Li et al 2015, after 2 days of the experiment, the plants were transferred to beakers containing freshly prepared solutions of the compounds. An increase in root and shoot length (elongation) of barnyardgrass seedlings was determined after 2 and 5 days of exposure to solution of phenolic compounds.…”

“…They can interact with cell membranes, alter ion fluxes, hydraulic conductivity of roots, and nutrient uptake (Einhellig 2004). Blum and Gerig (2005) concluded that the level of individual phenolic compounds is insufficient to inhibit plant growth, but rather their mixture or composition with other compounds.The concentration of phenolics in soil decreased due to their instability, and it has a great impact on their potential allelopathic properties (Li et al 2015).…”

“…The concentration of phenolics in soil decreased due to their instability, and it has a great impact on their potential allelopathic properties (Li et al 2015).…”