Marine natural products were the secondary metabolites of marine organisms with highly diversified structural features and varied bioactivities. It has been shown that marine-derived microorganisms were a rich source of unique chemical entities, and the algae-derived fungi remained to be less investigated so far. In this study, a number of fungal strains were isolated from marine algae collected from northeastern coast of Taiwan. In the preliminary antimicrobial screening against bacteria and fungi, including Escherichia coli DH5, Staphylococcus aureus YC981, Candida albicans SC5314, and Cryptococcus neoformans H99, the ethyl acetate extracts of liquid (potato dextrose broth) and solid (brown rice) fermented products of Acremonium sp. NTU492 isolated from the red alga Mastophora rosea were found to exhibit significant growth inhibitory activity against C. albicans and C. neoformans. Thus, a series of bioassay-guided fractionation and separation was undertaken, which has led to the isolation and identification of 13 compounds including 7 new compounds, namely acrepeptins A‒E (1‒5) and acremonisins A and B (6 and 7), along with previously reported 8-deoxy-trichothecin (8), cyclo[L-alanyl-L-threonyl-(2S)-2-hydroxy-3-methylbutanoyl-L-isoleucyl-(2S)-2-hydroxy-3-methylbutanoyl] (9), β-alanine, N-[N-[N-[N-[1-(2-hydroxy-4-methyl-1-oxopentyl)-L-prolyl]-L-isoleucyl]-N-methyl-L-valyl]-N-methyl-L-alanyl] (10), guangomide A (11), guangomide B (12), and brefeldin A (13). Their structures were elucidated by spectral analysis and compared with literatures [1, 2]. Of these, 8 exhibited significant antimicrobial activities against C. albicans and C. neoformans with MIC values of 2 and 0.5 μ
g/mL, respectively.
References
[1] Boot CM, Tenney K, Valeriote FA, Crews P. J Nat Prod 2006; 69: 83‒92.
[2] Boot CM, Amagata T, Tenney K, Compton JE, Pietraszkiewicz H, Valeriote FA, Crews P. Tetrahedron 2007; 63: 9903–9914.