Diterpenoids with herbicidal and antifungal activities from hulls of rice (Oryza sativa)

Abstract Diterpenoids are the main secondary metabolites of plants and with a range of biological activities. In the present study, 7 compounds were isolated from the hulls of rice ( Oryza sativa L.). Among them, 3 diterpenoids are new namely, 3,20-epoxy-3 α -hydroxy- 8,11,13-abietatrie-7-one ( 1 ), 4,6-epoxy-3 β -hydroxy-9 β -pimara-7,15-diene ( 2 ) and 2-(( E )-3- (4-hydroxy-3-methoxyphenyl) allylidene) momilactone A ( 3 ). While, 4 terpenoids are known, namely momilactone A ( 4 ), momilactone B ( 5 ), ent-7-oxo-kaur-15-en-18-oic acid ( 6 ) and orizaterpenoid ( 7 ) . The structures of these diterpenoids were elucidated using 1D and 2D NMR in combination with ESI-MS and HR-EI-MS. Furthermore, all isolated compounds displayed antifungal activities against four crop pathogenic fungi Magnaporthe grisea , Rhizoctonia solani , Blumeria graminearum and Fusarium oxysporum , and phytotoxicity against paddy weed Echinochloa crusgalli . The results suggested that rice could produce plenty of secondary metabolites to defense against weeds and pathogens.