Laboratory and Field Evaluation of the Phytotoxic Activity of <i>Sapindus mukorossi</i> Gaertn Pulp Extract and Identification of a Phytotoxic Substance

• Main Authors: Ziyang Dai, Jin Wang, Xiaojiang Ma, Jia Sun, Feng Tang
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Molecules
• Subjects: <i>Sapindus mukorossi</i>; saponin; phytotoxic activity; root growth inhibition; phytotoxic substance; weed control
• Online Access: https://www.mdpi.com/1420-3049/26/5/1318

Interest in finding plant-based herbicides to supplement synthesized herbicides is increasing. Although the extract of <i>Sapindus mukorossi</i> Gaertn has been reported to have herbicidal activity, little is known about phytotoxic substances and their efficacy of weed control in the field. To identify phytotoxic substances, the bioassay-guided fractionation by column chromatography and high-speed counter-current chromatography (HSCCC) was carried out. The phytotoxic activity assay, performed by the agar medium method, showed that the 70% ethanol fraction exhibited strong root growth inhibition against <i>Trifolium pratense</i> with an 50% inhibitory concentration (IC₅₀) value of 35.13 mg/L. An active compound was isolated from the 70% ethanol fraction and identified as hederagenin 3-<i><span style="font-variant: small-caps;">o</span></i>-<i>β</i>-D-xylopyranosyl-(1→3)-α-<span style="font-variant: small-caps;">l</span>-rhamnopyranosyl-(1→2)-α-<span style="font-variant: small-caps;">l</span>-arabinopyranoside (Compound A). Compound A had an IC₅₀ value of 16.64 mg/L. Finally, a new formulation was prepared based on the 70% ethanol fraction, which exhibited good efficacy against broadleaf weeds in a carrot field. The fresh weight control efficacy was 78.7% by 45 days after treatment at the dose of 1500 g a. i./ha. Hence, the extract of <i>S. mukorossi</i> pulp could be a promising supplement to the synthesized herbicides. Furthermore, compound A from <i>S. mukorossi</i> may be responsible for its phytotoxic activity.