Aqueous Extract from Leaves of Ludwigia hyssopifolia (G. Don) Exell as Potential Bioherbicide.

Ludwigia hyssopifolia (G. Don) Exell, one of the serious weeds in some rice-producing countries, was studied to determine its allelopathic potential based on the effects of aqueous extracts of its tissues (leaves, roots and stem) on seedling growth of selected weeds and rice. Major phenolic compound of its leaves was also isolated and characterized.

L. hyssopifolia aqueous leaf extract had significant inhibition on shoot growth and biomass accumulation of weeds (Amaranthus spinosus L., Dactyloctenium aegyptium L., Cyperus iria L.) while maintaining less adverse effects on rice (crop) compared to other aqueous extracts of roots and stem. Phytochemical screening showed that phenols, tannins, flavonoids, terpenoids, saponins and coumarins are found in its leaf aqueous extract. Folin-Ciocalteu method revealed that its leaves contain 26.66 ± 0.30 mg GAE g^-1 leaf. The extract was then acid-hydrolyzed to liberate the phenolics (25 mg phenolics g^-1 leaves). The major compound was isolated via preparative TLC using formic acid-ethyl acetate-n-hexane (0.05:4:6) solvent system. It had maximum UV absorbance at 272 nm while its FT-IR spectrum revealed phenol, carboxylic acid and ether functionalities. This also had similar chromatographic mobility when run together with syringic acid in two-dimensional paper chromatography and thin layer chromatography.

L. hyssopifolia has potential allelopathic activity and its leaf aqueous extract showed the highest phytotoxic activity (P≤0.05) indicating its potential as bioherbicide. The most probable identity of the major phenolic compound is syringic acid. This article is protected by copyright. All rights reserved.