Phytotoxicity of Vulpia residues:: II.: Separation, identification, and quantitation of allelochemicals from Vulpia myuros

Phytotoxicity-based extraction and fractionation were employed to separate and purify the allelochemicals from an aqueous extract of vulpia (Vulpia myuros) residues. Further analyses, identification, and quantitation of these allelochemicals were conducted by gas chromatography-mass spectrometry on the most toxic fraction. Twenty-one compounds were identified in the ether Fraction from the vulpia residue aqueous extract. They were catechol, hydroquinone, 3,4-dimethoxyphenol, pyrogallol, coniferyl alcohol, and benzoic, succinic, hydrocinnamic, salicylic, protocatechuic, vanillic, gentisic, syringic, p-hydroxybenzoic, alpha-hydroxybenzenepropanoic, p-hydroxyphenylacetic, p-hydroxybenzenepropanoic, hydroferulic, p-coumaric, hydrocaffeic, and ferulic acids. A chromatographic internal standard method with multiple-point calibration graphs was used to quantify the identified compounds. Quantities in the vulpia residues ranged from 1.36 to 81.0 mu g/g dry residue, in total accounting for 0.05% of the dry weight residue. The combined syringic and hydroferulic acids were present in the largest amount, 140.11 mu g/g residue. Vanillic, succinic, p-hydroxybenzenepropanoic, and salicylic acids were next in amount, ranging from 37.24 to 81.24 mu g/g residue. Catechol, hydrocinnamic acid, and hydroquinone were present in the smallest quantities, ranging from 1.36 to 1.82 mu g/g residue. The remainder of the compounds were intermediate in amount, ranging from 2.33 to 18.1 mu g/g residue.