PURIFICATION AND IDENTIFICATION OF SORGOLEONE AND ITS QUANTIFICATION IN SORGHUM (Sorghum bicolor L. Moench) GENOTYPES

Isolation, characterization and quantification of potential allelopathic compounds are fundamental for determination of their single biological activity or with other compounds. This work aimed to purify and to identify the main substance in hydrophobic extracts of sorghum roots, and to determine the production variability and purity of the quinone sorgoleone in sorghum genotypes. Roots of 41 sorghum genotypes were immersed in dichloromethane solution contaminated with acetic acid for the obtention of total hydrophobic extracts and its concentration in dry matter. The extracts of five sorghum genotypes (RS 11, 741, BR 601, HYC 42 and BR 304) were purified by column (CC) chromatography and analyzed by magnetic resonance of protons spectroscopy (NMR-H) and high performance liquid chromatography (HPLC). The sorgoleone, in its oxidized form {2 hidroxi-5-metoxi-3-[(8'z, 11'z)-penta-deca -8', 11', 14'-trien-1-il]-p-benzoquinone} constitutes the main component (73 to 82%) in extracts. The production of hydrophobic extracts in 100 roots ranged from 0.35 mg to 2.98 mg while its concentration in dry mater from 5.26 mg. g(-1) to 27.5 mg. g(-1). The amount of hydrophobic extracts produced by 41 sorghum genotypes followed the Gauss distribution, with the majority of genotypes producing the intermediary amount of the compounds reported above.