Green water-dispersible coarse powder nano-formulation for allelopathic leaf extract of Mikania micrantha Kunth ex H.B.K. in controlling the rice weed Echinochloa colona (L.) Link

Abstract

Plant extracts originated from an exotic species, Mikania micrantha Kunth ex H.B.K. have shown appreciable phytoinhibitory activities against a rice weed, Echinocloa colona (L.) Link. In spite of that, the glutinous extracts exhibit poor physicochemical properties preventing it from delivering efficiently and for ease of application. This research study aimed to formulate the leaf extract of M. micrantha with pre-emulsions and lignocellulosic coarse powder for the sake of ameliorated bioefficacy of the extract via nano-delivery system and improved product handling. Three pre-emulsions were developed using rapeseed oil methyl esters (ROME) and disparate bisurfactant mixtures including polyalkoxylated fatty alcohol (PAFA)-alkyl sulfonate (AS), PAFA-cocamidopropyl betaine (CB) and PAFA-alkyl polyglucosides (APG). The pre-emulsions were incorporated with leaf extracts containing the phenolic allelochemicals. The pre-emulsified extracts were loaded onto mercerized lignocellulose by solvent percolation and evaporation (SPE) technique produced the formulated water-dispersible coarse powders, WDP-F1, WDP-F2 and WDP-F3. A non-formulated extract was prepared into water-dispersible powder, WDP-EX for quality control. The results show greater water absorption by the formulated powders in prolonged duration of 7 days exerted the release of higher total amount of phenolic compounds (63.66–86.52%) than the phenolics amount released from the non-formulated powder (41.98%). Transmission electron microscopy (TEM) revealed the formulated extracts exhibited particles release in regular patterns from three dimensional networks and gigantic vesicles, unlike the non-formulated extract liberated uneven particles from disordered aggregates. The particles released from the formulated powders displayed low mean sizes (87.56–103.27 nm) in monodisperse range (PDI = 0.180–0.203). In opposition, non-formulated particles indicated larger mean size (423.93 nm) and polydisperse (PDI = 0.550). In the glasshouse study, the formulated powders promoted significantly higher inhibitions of germination, shoot height, fresh weight and dry weight of E. colona than non-formulated powder and non-treated weedy control. Moreover, the paddy seedling growth and grain yield treated with the formulated powders were statistically equivalent (p = 0.05) to treated with a commercial formulation, Satunil® and weed-free non-treated control. These valuable outcomes genuinely reflected the inspirational use of green water-dispersible coarse powder in the formulation of natural products in fostering the sustainable development of crop protection products.