Antibacterial diterpenes and their fatty acid conjugates from rice leaves

Abstract Six structurally oryzalide-related compounds, oryzadione ( 1 ), 2 , 3 , 4 , 5 and 6 , were isolated from a neutral fraction of the extract of healthy leaves using a bacterial leaf blight-resistant cultivar of a rice plant, “Norin-27”, as a group of antimicrobial substances. Their structures were determined by spectroscopic studies to be kaurane analogues and kaurane analogues conjugated with fatty acids, i.e., 1 : ent -15,16-epoxy-kauran-2,3-dione (enol form: ent -15,16-epoxy-2-hydroxy-kauran-1-en-3-one), 2 : ent -15,16-epoxy-3β-hydroxy-kauran-2-one, 3 : ent -15,16-epoxy-3-oxa-kauran-2-one, 4 : ent -15,16-epoxy-3β-myristoyloxy-kauran-2-one, 5 : ent -15,16-epoxy-3α-palmitoyloxy-kauran-2-one, and 6 : ent -15,16-epoxy-2β-palmitoyloxy-kauran-2-one.