Chemical profile, antioxidant activities and allelopathic potential of liquid waste from germinated brown rice

We examined the liquid waste of germinated brown rice (Oryza sativa L.) (GBR) fortotal phenols, flavonoids and antioxidant and allelopathic activities. The butanol extract showedthe strongest antioxidant activity, while the ethyl acetate extract exhibited maximal inhibition ongermination and growth of radish (Raphanus sativus L.). Total flavonoid content was reverselyproportional to allelopathic level (r2=0.63), whilst antioxidant activities showed negligiblecoefficient correlations. Analysis of GC-MS (gas chromatography mass spectrometry) revealedthe presence of many putative constituents, of which 1-propene-1,2,3-tricarboxylic acid, tributylester was the principal compound in butanol, acetate and hexane extracts. There were 18, 6, 12 and3 compounds putatively identified in butanol, ethyl acetate, hexane and aqueous extracts,respectively. In the butanol extract, 2,3-dihydro-benzofuran, phenyl ester carbamic acid,2-methoxy-phenol, 3,4-diol-1,5-heptadiene, 1-(2-hydroxy-5-methylphenyl)-ethanone and methylester-3- (4-hydroxyphenyl)-2- propenoic acid were the predominant substances. In the ethylacetate extract, methyl ester-hexadecanoic acid and methyl ester-9-octadecenoic acid and bis(2-ethylhexyl) ester-hexanedioic acid were the dominant compounds. In the hexane extract,methyl ester-hexadecanoic, n-hexadecanoic acid, methyl ester-9-octadecenoic acid,10-hydroxy-methyl ester-hexadecanoic acid and E-2-((hex-3-enyloxy) carbonyl) benzoic acidpodocarpan-12ß-ol were the major constituents. There were three key substances observed in theaqueous extract, including acoradien, ß-cis-caryophyllene and monoethanoamine. The compoundsidentified in the liquid waste of GBR production might be potential for weed management.