Distribution of different forms ofp-hydroxybenzoic, vanillic,p-coumaric and ferulic acids in forest soil

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Abstract
We studied the isolation of the three different forms, A, B and C, in which p-hydroxybenzoic, vanillic, p-coumaric and ferulic acids exist in forest soil as well as their relative distributions by gas liquid chromatography. Form A is designated as the free form, which was isolated with hot ethyl acetate by repeated refluxing and is significant for allelopathic studies. Form B is a combined form, which was extractable with hot ethyl acetate. Form C is another combined form, which was unextractable with hot ethyl acetate but could be isolated with hot 2 m NaOH by repeated extraction. The latter form appears to be bound to the soil matrix and not to move easily in the soil environment. The relative distributions of p-hydroxybenzoic acid in the A, B and C forms were 4, 4 and 92%, respectively; those of vanillic acid were 3, 5 and 92%, respectively; those of p-coumaric acid were 2, 41 and 57%, respectively; and those of ferulic acid were 1, 35 and 63%, respectively. A brief comparison with previous data for a peat soil is also given.