Methanol Extracts of Helianthus annuus and Bambusa vulgaris Leaves Exert Herbicidal Effects on Two Selected Weeds in vitro

Abstract

Weed control using synthetic herbicides often poses adverse consequences for the environment and human health. The integration of bioherbicides into weed management strategies has recently been introduced as an alternative. Helianthus annuus and Bambusa vulgaris have been reported to exhibit allelopathic effects on other plants. This study elucidated the phytochemicals in the methanol leaf extracts of H. annuus and B. vulgaris and evaluated their in vitro herbicidal effects on two weeds. Helianthus annuus leaf methanol extract (HALME) and Bambusa vulgaris leaf methanol extract (BVLME) were subjected to Gas Chromatography-Flame Ionization Detection (GC-FID) and High-Performance Liquid Chromatography (HPLC) for compound analysis. The in vitro effects of HALME and BVLME were tested on the activities of superoxide dismutase (SOD), catalase, glutathione-S-transferase (GST), acetolactate synthase (ALS), thioesterase and Photosystems I and II in fresh leaf extracts of Tridax procumbens and Alternanthera sessilis weeds. The GC-FID identified Cinnamic Acid, Heliannone A, Kukukanin B, Paniculoside A, Helikauranoside A and Niranthin in HALME, and p-Coumaric acid, Iso-orientin, Luteolin, and 8-C-Glycosylapigenin in BVLME. The HPLC measured Heliannone A, Kukukanin B, Paniculoside A and Helikauranoside A in HALME, and Luteolin and 8-C-Glycosylapigenin in BVLME. Both HALME and BVLME significantly (p < 0.05) reduced SOD, catalase and GST activities in T. procumbens and A. sessilis, with effects comparable to those of glufosinate and glyphosate. BVLME, glufosinate, glyphosate and their combination significantly (p < 0.05) reduced ALS activity in A. sessilis and T. procumbens and thioesterase activity in A. sessilis relative to the control. Both extracts also reduced photosystems I and II activities in the weed extracts. These findings indicate that the tested leaf extracts influence multiple biochemical processes associated with weed metabolism and stress responses, supporting further evaluation of their herbicidal potential under whole-plant and field conditions.