Utilization of Phenolic Compounds Extracted from Agro-Industrial Wastes as Natural Herbicides

Abstract

Phenolic compounds are considered one of the most important secondary metabolites categories in plant that involved in allelopathic effect. Allelopathy is a chemical interaction between plants and could be defined as the stimulatory or inhibitory effects of a plant on the growth of another plant through the release of secondary compounds. The phenolic compounds, in orange juice peel waste (ORPW), olive oil mill waste (OLMW) and mango leaves waste (MLW), were extracted, then identified and determined by HPLC. The allelopathic effect of ORPW, OLMW and MLW aqueous extracts, at successive concentrations, was examined on germination and growth of two weed species (Phalaris minor Retz. and Malva parviflora L.) in petri dishes and pots bioassays. The main detected phenolic compounds were ferulic, chrysin, sinapic, p-hydroxybenzoic, quercetin and rosmarinic in ORPW extract, vanillic, cateachin, rutin, protocatechuic and gallic in MLW extract, and gallic, p-coumaric, protocatechuic, p-hydroxybenzoic, vanillic and ferulic in OLMW extract. The aqueous extracts of ORPW recorded the highest concentration of phenolic compounds and were the most effective in inhibition the germination and growth of both weed species followed by MLW and OLMW in petri dishes and pots trails. It can be concluded that the aqueous extracts of ORPW and MLW wastes have high contents of phenolic acids and could be utilized in controlling weeds as natural herbicides.