A New Chlorinated Tetralone from Co-Culture of Insect-Pathogenic Beauveria bassiana and Phytopathogenic Nigrospora oryzae

In this study, the co-culture of Nigrospora oryzae and Beauveria bassiana , the pathogenic endophytes in the seeds of Dendrobium officinale , were examined for their antagonistic relationship by the production of metabolite. One new chlorotetralone ( 1 ) and five known compounds, murranoic acid A ( 2 ), 9,12,13-trihydroxy-10-octadecenoic acid ( 3 ), 3,3′-methylenebis(4-hydroxy-6-methyl-2 H -pyran-2-one) ( 4 ), sclerin ( 5 ), and (4S)-4,6,8-trihydroxy-3,4-dihydro-1(2 H )-naphthalen-1-one ( 6 ), were isolated. Compounds 1 – 5 showed antifungal activity against B. bassiana with MICs of 256, 128, 2, 32, and 64 μg/mL, and N. oryzae with MICs of 64, 256, 256, 256, and 64 μg/mL. Compound 4 showed significant antifungal activity against co-culture of B. bassiana and N. oryzae with MIC at 1 μg/mL.