CHARACTERISTICS OF THE GREEN FRACTION OF P TYPE HUMIC ACID

概要

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P type humic acid which has absorption bands near 615,570,and 450 nm due to the presence of dihydroxyperylenequinone(DHPQ)was investigated by gel-chromatography.Humic acid samples were fractionated using Sephadex G-50 as gel material and 0.1 N NaOH, with or without 1.5 M urea, as eluent.The absorption spectra of the effluent fractions were measured, and elution curves were drawn on the basis of the optical density at 600 nm. In general, the intensity of the absorption bands due to DHPQ increased with increasing fraction number, accompanied by a change in effluent color from brown, greenish brown to green. Based on the elution curves, the effluent fractions of a humic acid containing a large amount of the green fraction were divided into six groups : B_1,B_2,BG, G_1,G_2,and G_3.These fraction groups, especially the G groups and cercosporin, a dihydroxyperylenequinone pigment, were compared by absorption spectroscopy, ultrafiltration, ultimate analysis, TLC, and gel-chromatography. The green fraction was composed of a non-humic, relatively lower-molecular weight polymer containing a considerable amount of DHPQ nucleus, while the brown humic fraction still maintained the characteristic light absorption due to DHPQ.It may be tentatively concluded that the green fraction is not only a co-extracted impurity, but is also firmly associated with dark-colored humic substances.
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