title: Two compounds from allelopathic rice accession and their inhibitory activity on weeds and fungal pathogens.
abstract: A flavone (5,7,4'-trihydroxy-3',5'-dimethoxyflavone), a cyclohexenone (3-isopropyl-5-acetoxycyclohexene-2-one-1) and a liquid mixture of low polarity, containing long-chain and cyclic hydrocarbons, were isolated from leaves of allelopathic rice accession PI 312777 using column chromatography. Their structures and constituents were identified by means of HR-MS, NMR and GC/MS analyses, respectively. Bioassays showed that both the flavone and cyclohexenone significantly inhibited the growth of weeds Echinochloa crus-galli, Cyperus difformis and Cyperus iris, and the spore germination of fungal pathogens Pyricularia oryzae and Rhizoctonia solani at all tested concentrations. Moreover, the combination of the inactive mixture of low polarity and the active flavone or cyclohexenone significantly enhanced the inhibitory activities on weed growth. In addition, the two compounds and the mixture of low polarity from the leaves of PI312777 did not inhibit the rice growth at the same concentrations. It was also established that both compounds could be released into the soil, and was especially induced by E. crus-galli. The results suggest that 5,7,4'-trihydroxy-3',5'-dimethoxyflavone and 3-isopropyl- 5-acetoxycyclohexene-2-one-1 may act as allelochemicals participating in the defense of rice against weeds and pathogens.
authors.affiliation: Institute of Tropical and Subtropical Ecology, South China Agricultural University, Guangzhou, China. chkong@scau.edu.cn
authors.forename: Chuihua
authors.initials: C
authors.lastname: Kong
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Xu
authors.forename: Bin
authors.initials: B
authors.lastname: Zhou
authors.forename: Fei
authors.initials: F
authors.lastname: Hu
authors.forename: Chaoxian
authors.initials: C
authors.lastname: Zhang
authors.forename: Maoxin
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000383:Agriculture; D003512:Cyclohexanones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005659:Fungicides, Industrial / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006540:Herbicides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D020082:Magnaporthe / Q000187:drug effects / Q000502:physiology; D015394:Molecular Structure; D012275:Oryza / Q000737:chemistry* / Q000254:growth & development; D010572:Pest Control, Biological; D018515:Plant Leaves / Q000737:chemistry; D012232:Rhizoctonia / Q000187:drug effects / Q000502:physiology; D012987:Soil / Q000032:analysis; D013172:Spores, Fungal / Q000187:drug effects / Q000502:physiology
chemical_list: D003512:Cyclohexanones; D005419:Flavonoids; D005659:Fungicides, Industrial; D006540:Herbicides; D012987:Soil; C017769:tricin