Dimeric cyanobacterial cyclopent-4-ene-1,3-dione as selective inhibitor of Gram-positive bacteria growth: Bio-production approach and preparative isolation by HPCCC

Abstract

a b s t r a c tThe need for new antimicrobial agents is greater than ever because of the emergence of multidrug resistance in common pathogens and incidence of new infections. Cyclopent-4-ene-1,3-diones (CPDs) have been reported as a new class of compounds with promising antimicrobial and antifungal properties. Herein we report the selective antibiotic properties of nostotrebin 6, a phenolic CPD produced biotechnologically by the culture of cyanobacterium Nostoc sp. str. Lukešová 27/97. High performance countercurrent chromatography (HPCCC) combined with gel permeation chromatography (GPC) was used for the isolation of nostotrebin 6 with a relatively high 0.53 ± 0.1% yield (calculated from dried biomass) and final purity higher than 96%. Nostotrebin 6 was tested for its antimicrobial and antifungal activities by using standard micro-dilution method, and the results were expressed as minimal inhibitory concentrations (MICs). Nostotrebin 6 unequivocally inhibited the growth of Gram-positive reference (Enterococcus faecalis CCM 4224, Staphylococcus aureus CCM 4223 and Staphylococcus aureus CCM 3953) and multidrug-resistant (Staphylococcus haemolyticus A/16568, Staphylococcus aureus MRSA 4591 and Enterococcus faecium VanA 419/ana) strains. Its strongest effect was exerted against the Gram-positive bacteria with MICs ranging between 6.25 and 15.6 μg/mL. There was no effect on Gram-negative strains tested and yeasts. Our results suggest that nostotrebin 6 could serve as basic nucleus for further design of novel antibiotic agents and demonstrate that the bio-production approach based on HPCCC/GPC isolation endpoint is an efficient methodology for obtaining nostotrebin 6 in multi-gram scale. Furthermore, the presented isolation method can be easily up-scaled to process kilograms of the cyanobacterial biomass.

Nostotrebin 6 Related Cyclopentenediones and δ-Lactones with Broad Activity Spectrum Isolated from the Cultivation Medium of the Cyanobacterium Nostoc sp. CBT1153

“…biomass extract by Zelik et al in 2010. 30 Because we later isolated the compound for comparative bioactivity testing, the dereplication was also confirmed by one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) data.…”

“…Our results also confirmed published data concerning the antimicrobial activity of compound 1 against selected Gram-positive bacteria. 30 Compound 1 and the two tested derivatives were active against B. subtilis 168, E. faecium BM4147-1, and S. aureus ATCC29213, with MICs of 13 μM for compound 1, 3−13 μM for compound 6, and 50−100 μM for compound 3 (Table 3).…”

“…27 Although HPLC analysis of this extract revealed compound 1 as the main compound, several minor peaks were detected as well but not characterized at that time. 28 Compound 1 was also found to be cytotoxic and pro-apoptotic on mouse fibroblasts (BALB/c) 29 as well as antibacterial against Gram-positive bacteria (Table S1 of the Supporting Information) 30 and suggested as lead structure for drug development. 24 However, because compound 1 is a polyphenolic compound, caution might be appropriate.…”

“…24 In the case of compound 1, a protective role against biotic stress was suggested as well. 30 Our study might affirm this reasoning, as the nostotrebins/nostolactones were found to be present in the cultivation medium. Another potential ecological role of the CPDs might be protection against UV irradiation.…”

“…27,28 In addition, cytotoxicity and pro-apoptotic activity on mouse fibroblasts as well as antimicrobial activity, especially against Gram-positive bacteria, have been reported for the compound. 29,30 Often, cyanobacterial specialized metabolites show pronounced cytotoxicity, but another activity that is frequently observed for cyanobacterial non-ribosomal peptides is the inhibition of proteases. 31−36 The cathepsin L-like cysteine protease rhodesain plays an important role during human infection with Trypanosoma brucei, known as human African trypanosomiasis (HAT).…”