We have isolated a new nitrobenzoyloxy-substituted sesquiterpene, insulicolide A (1), from the chemically unexplored fungus Aspergillus insulicola. Low temperature X-ray crystallography established that 1 is the 6-p-nitrobenzoate of 6â,9R,14-trihydroxycinnamolide (Figure 1). A. insulicola is one of the few known marine aspergilli2 and has been accepted as a distinct species by several authors.3-5 It is related to the ascomycete genus Petromyces in the Eurotiales.Five strains of A. insulicola were isolated from marine sources, collected in the Bahamas in 1993. The strains were fermented on two or three different media: CYA (yeast extract 5 g/L, sucrose 30 g/L), YES (yeast extract 20 g/L, sucrose 150 g/L), and SB (potato starch 75 g/L, soybean meal 40 g/L, sea salts 40 g/L), and the mycelia and media were extracted with EtOAc. The neurotoxin asteltoxin6 and 1 were isolated by liquid chromatography of extracts from two strains grown on CYA. The metabolite production of the five strains of A. insulicola was compared by HPLC diode-array analysis. Production of 1 and asteltoxin was shown to be dependent on medium but not on the origin of the fungi. Formation of 1 was established from the cultures on CYA and SB, but only in very small amounts or not at all on YES medium. Asteltoxin was detected only on CYA and SB media.HPLC diode-array analyses of extracts of several terrestrial isolates of the same species of fungus7 were compared with those of marine isolates. According to these analyses, penicillic acid,8 4-hydroxymellein,9 xanthomegnin,10 viomellein,11 vioxanthin,12 asteltoxin,6 and some unknown compounds are consistently expressed by A. insulicola. One of the major compounds has now been isolated and named insulicolide A (1). According to HPLC analysis, 1 was also produced by terrestrial isolates of A. bridgeri and some isolates of A. sclerotiorum, but not by any other species related to the genus Petromyces (Aspergillus subgenus Circumdati section Circumdati, formerly the Aspergillus ochraceus group). Insulicolide A is thus a good chemotaxonomic marker for the three species (details to be reported elsewhere).The tricyclic sesquiterpene skeleton in 1 has not previously been thoroughly characterized by X-ray.13