Chemical constituents of marine mangrove-derived endophytic fungus Alternaria tenuissima EN-192

A chemical investigation of the ethyl acetate extract of the fermentation broth of Alternaria tenuissima EN-192, an endophytic fungus obtained from the stems of the marine mangrove plant Rhizophora stylosa , resulted in the isolation of nine known secondary metabolites, including four indole-diterpenoids: penijanthine A ( 1 ), paspaline ( 2 ), paspalinine ( 3 ), and penitrem A ( 4 ); three tricycloalternarene derivatives: tricycloalternarene 3a ( 5 ), tricycloalternarene 1b ( 6 ), and tricycloalternarene 2b ( 7 ); and two alternariol congeners: djalonensone ( 8 ) and alternariol ( 9 ). The chemical structures of these metabolites were characterized through a combination of detailed spectroscopic analyses and their comparison with reports from the literature. The inhibitory activities of each isolated compound against four bacteria were evaluated and compounds 5 and 8 displayed moderate activity against the aquaculture pathogenic bacterium Vibrio anguillarum , with inhibition zone diameters of 8 and 9 mm, respectively, at 100 μg/disk. To the best of our knowledge, this is the first report on the secondary metabolites of mangrove-derived A lternaria tenuissima and also the first report of the isolation of indole-diterpenoids from fungal genus A lternaria .