Isolation and Characterization of Antifungal Metabolites from the -Associated Fungus .

Two biosynthetically related new metabolites, eucalyptacid A () and eucalactam B (), along with six known compounds (-), eugenitol (), cytosporone C (), 4-hydroxyphenethyl alcohol (), 1-(4-hydroxyphenyl)ethane-1,2-diol (), -(2-hydroxy-2-phenylethyl)acetamide (), and phomopene (), were isolated from the solid rice cultures of the endophytic fungus KY-9 that had been isolated from . Also, two further new derivatives (, ) were prepared from . The structures were elucidated by exhaustive analysis of NMR and ESIMS data and chemical methods such as Marfey's protocol. Compound was identified as a rare polyketide fatty acid, (8)-3,5,11-trihydroxy-2,10,12-trimethyltetradecenoic acid, and was determined to be the first cyclic depsipeptide containing the same fatty acid unit as and a Gly-Gly-Thr tripeptide chain. Its N-terminal end is N-acylated by an 11-hydroxy fatty acid with a branch alkyl chain of 14:1. The 11-hydroxyl group connects to the carboxylic group of the C-terminal amino acid to form a 22-membered lactone ring. A hypothetical biosynthetic pathway for the new polyketides is proposed. The isolated compounds were assayed for their inhibition against four plant pathogenic fungi, , , , and . Compounds , , , and exhibited antifungal activities against , with minimal inhibitory concentration (MIC) values from 6.25 to 50 μM. Thus, strain KY-9 represents an untapped source for the development of biological control agents to prevent the infection of pathogenic fungus .