Chavibetol: Major and Potent Phytotoxin in Betel (Piper betle L.) Leaf Essential Oil.

Abstract

Many essential oils and their constituting volatile organic compounds are known to be phytotoxic and potential bioherbicides. This study aims to investigate the phytotoxicity of propenylbenzene-rich essential oils and identify active molecule(s) therein. Five commercially available propenylbenzene-rich oils were screened, of which betel (Piper betle L.) oil was identified as a potent natural phytotoxin. It dose-dependently inhibited the wheatgrass (Triticum aestivum) seed germination and growth in water and agar medium with half maximal inhibitory concentration (IC50 ) in the range 23.2-122.7 μg/mL. Phytotoxicity-guided fractionation and purification revealed chavibetol as the major and most potent phytotoxic constituent of betel oil, followed by chavibetol acetate. The structure-activity relationship study involving twelve propenylbenzenes indicated the structural and positional importance of aromatic substitutions for the activity. Further, phytotoxic efficacy of chavibetol was established against wheatgrass germination and growth in water (IC50 15.8-53.4 μg/mL), agar (IC50 34.4-53.6 μg/mL) and aerial (IC50 1.7-4.5 mg/L) media with more pronounced effect on the radicle. Also, in open phytojar, it efficiently inhibited the growth of 3-7 days old bermudagrass (Cynodon dactylon) seedlings when sprayed directly (IC50 2.3-3.4 mg/jar) or supplemented in agar (IC50 116.6-139.1 μg/mL). The growth of pre-germinated green amaranth (Amaranthus viridis) was inhibited more effectively in both the application modes (1.2-1.4 mg/jar and IC50 26.8-31.4 μg/mL respectively). The study concluded betel oil as a potent phytotoxic herbal extract and its major constituent chavibetol as a promising volatile phytotoxin for the future management of weeds in their early phase of emergence. This article is protected by copyright. All rights reserved.