Phenolic compounds in NaOH extracts of UK soils and their contribution to antioxidant capacity

摘要

Antioxidants are released during the extraction of soils with NaOH, which also releases phenolic compounds from plant and soil material. This raises the possibility that phenolics are important contributors to the antioxidant capacity (AOC) of soils.Both the AOCs and the concentrations of 12 phenolic compounds were measured in NaOH extracts of a range of UK soils. Samples of surface and subsurface horizons were taken from 24 sites representing the major soil types (brown soils, gleys, podzols, peatsand lithomorphic soils). The internal standards method was used to quantify the phenolics, which were detected by gas chromatography. The AOC of the extracts was measured using the ABTS free radical method. There were differences in the phenolic distributions extracted from soils with different land uses/plant inputs, as well as differences between surface and subsurface samples. A linear relationship was found between the AOCs of the extracts and the sum of the phenolic compounds. The AOCs of the individual phenolic compounds were also measured. The calculated contribution of the individual phenolics to the AOC of the extracts was small and less than 10% of the total AOC in all cases. Thus the measured phenolic compounds were not important contributors to the AOCs, and other unidentified antioxidant compounds were probably present.