Aspergicin, a new antibacterial alkaloid produced by mixed fermentation of two marine-derived mangrove epiphytic fungi

Abstract

A new alkaloid designated as aspergicin (1), together with a previous secondary metabolite, neoaspergillic acid (2), and a common compound, ergosterol (3), were isolated from the mixed cultured mycelia of two marine-derived mangrove epiphytic Aspergillus sp. fungi. Extensive application of 1D and 2D NMR techniques was made to characterize the structure and to establish the 1 H and 13 C assignments of compound 1. In the antibacterial assays, both compounds 1 and 2 showed significant antibacterial activity against some selected Gram bacteria.Application of mixed fermentation was proved to contribute to the discovery of new natural products from marinederived microorganisms. To date, at least nine new biologically active compounds have been identified by mixed fermentation of marine-derived microorganisms, pestalone [1], libertellenones A-D [2], marinamides A and B [3], and emericellamides A and B [4]. Results of mixed fermentation include increased antibiotic activity in the crude extract, increased yields of previously described metabolites, increased yields of previously undetected metabolites, analogues of known metabolites resulting from combined pathways, and induction of previously unexpected pathways for bioactive constituents [5].Marine-derived mangrove fungi were proved to be an abundant resource for novel natural compounds [6,7]. As part of our ongoing search for new bioactive metabolites from mixed fermentation of marine-derived mangrove fungi from the South China Sea [3,8], two antibacterial compounds, neoaspergillic acid and kojic acid, were obtained as major secondary metabolites from the mixed fermentation liquid of two marine-derived mangrove epiphytic Aspergillus fungi, which were isolated from a rotten fruit of mangrove Avicennia marina in the South China Sea [9]. Further chemical investigations of the mixed fermentation mycelia resulted in the isolation of a new alkaloid designated as aspergicin (1), together with a previous secondary metabolite, neoaspergillic acid (2), and a commom compound, ergosterol (3). We report herein their isolation, structural elucidation, and antibacterial activities. Fig. 1. The structure and key HMBC correlations (from C to H) of compound 1.

The Berkeleylactones, Antibiotic Macrolides from Fungal Coculture

“…Tbp-5 and Mycogone rosea DSM 12973 led to the formation of new lipoaminopeptides, acremostatins A, B, and C. 16 The antibacterial alkaloid aspergicin was derived from coculture of two Aspergillus species. 17 In two separate coculture experiments, the mangrove fungi Phomopsis sp. K38 and Alternaria sp.…”

Endophytic fungi: a reservoir of antibacterials

“…Aspergicin (154) has anti-bacterial activity against S. aureus , S. epidermidis , B. subtilis , B. dysenteriae, B. proteus , and E. coli , with MICs of 62.5, 31.25 15.62, 15.62 62.5, and 31.25 μ g/mL respectively. Neoaspergillic acid (155) has antibacterial activity against S. aureus , S. epidermidis , B. subtilis , B. dysenteriae, B. proteus , and E. coli , with MICs of 0.98, 0.49, 1.95, 7.8, 7.8, and 15.62 μ g/mL respectively (Zhu et al, 2011 ).…”

Liquid Fungal Cocultivation as a Strategy to Access Bioactive Metabolites

“…Conversely, the coculture of 2 marine Aspergillus sp. fungi resulted in the production of 2 antibacterial compounds (aspergicin and neoaspergillic acid) that were active against S. aureus, S. epidermis, Bacillus subtilis, B. dysenteriae, B. proteus, and E. coli [14].…”