Antimicrobial and antioxidant properties of the crude peptide extracts of Galatea paradoxa and Patella rustica

Borquaye et al. SpringerPlus (2015) 4:500 DOI 10.1186/s40064-015-1266-2 Open Access RESEARCH Antimicrobial and antioxidant properties of the crude peptide extracts of Galatea paradoxa and Patella rustica Lawrence Sheringham Borquaye*, Godfred Darko, Edward Ocansey and Emmanuel Ankomah Abstract This study evaluated the antimicrobial and antioxidant activities of crude peptide extracted from Galatea paradoxa (G. paradoxa) and Patella rustica (P. rustica). The extracts were tested against eight strains of bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, Enterococcus feacalis, Klebseilla pneumoniae, Streptococcus pneumoniae, Pseudomonas aeruginosa) and one strain of fungi (Candida albicans) using agar well diffusion and broth dilution assays. The extracts from G. paradoxa demonstrated a high degree of activity against the bacteria strains but were inactive towards the fungus. P. rustica, however, showed a markedly higher antifungal activity but little antibacterial effect. The minimum inhibitory concentrations (MIC) of the extracts determined by the broth tube dilution assay were 17 mg/mL of G. paradoxa against the entire spectrum of microorganisms tested except for C. albicans which was 20 mg/mL. The MIC of the extracts of P. rustica was 13 mg/mL against all the strains of microorganisms tested except for E. feacalis (17 mg/mL), K. pneumoniae (17 mg/mL) and C. albicans (13 mg/mL). Antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed scavenging ability on the DPPH radical was 56.77 % at 0.39 mg/ mL for G. paradoxa and 79.77 % at 0.39 mg/mL for P. rustica. The study indicates that the crude peptide extracts from the two molluscs have promising antimicrobial and antioxidant activities that can be harnessed as leads for potential bioactive compounds. Keywords: Bacteria, Fungi, Bioactive compounds, Marine molluscs, Freshwater molluscs Background In recent years, there have been a rise in infectious disease cases all over the world. The emergence and/or reemergence of some of these infectious diseases such as the deadly Ebola viral disease (EVD) have had crippling economic and social impacts in countries affected. This, coupled to the fact that drug resistant pathogens are evolving at a much faster rate than new drugs are being discovered, has heightened the need to search for new classes of antimicrobial agents. The indiscriminate use of drugs to manage infectious diseases have not helped the situation. Many scientists and research programs are therefore prospecting for new antimicrobial agents from plants and animal sources. *Correspondence: Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana Marine invertebrates have proven to be rich sources of bioactive compounds with activities ranging from antimicrobial to antitumor (Martins et al. 2014; Leal et al. 2012; Thakur et al. 2005). Due to the fact that they exhibit broad spectrum antimicrobial activity, possess selective toxicities and are less prone to microbial resistance, antimicrobial peptides represent an exciting class of bioactive compounds that could potentially provide major reprieve for mankind in the efforts to curb/control infections. Because marine invertebrates rely solely on innate immune mechanisms for defense, they represent a potentially rich source for pharmacologically useful antimicrobial peptides (Otero-González et al. 2010). Ghana possess a coastline of about 550 km with different types of aquatic habitat ranging from deep sea hydrothermal vent to intertidal regions. In addition, a number of freshwater habitats can be found all over the country. These aquatic habitats are home to a wide variety of invertebrates © 2015 Borquaye et al. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Borquaye et al. SpringerPlus (2015) 4:500 Page 2 of 6 Table 1 Zone of Inhibition (mm) of extracts of Galatea paradoxa and Patella rustica against test microorganisms Galatea paradoxa E. coli S. aureus B. subtilis S. typhi E. feacalis C. albicans K. pneumoniae S. pneumoniae P. aeruginosa 19.7 ± 0.6 20.0 ± 0.0 20.3 ± 0.6 15.3 ± 0.6 16.0 ± 1.0 0.0 ± 0.0 Patella rustica 0.0 ± 0.0 36.3 ± 1.2 3.0 ± 0.0 14.7 ± 0.6 2.0 ± 0.6 19.0 ± 1.0 2.0 ± 1.0 35.3 ± 0.6 15.0 ± 1.0 34.7 ± 0.6 37.0 ± 1.0 14.7 ± 0.6 16.7 ± 1.15 20.3 ± 1.5 2.3 ± 1.15 20.3 ± 0.6 Positive control (ciprofloxacin) 41.0 ± 2.0 35.0 ± 0.0 0.0 ± 0.00 Values reported as mean ± standard deviation. Mean of three experiments 15.0 ± 1.7 35.3 ± 1.2 Negative control (25 % ACN/0.1 % TFA) – – – – – – – – – Zone in mm indicates the distance from the border of the disc to the edge of the clear zone ACN acetonitrile, TFA trifluoroacetic acid (Ministry of Environment and Science 2002). Research geared towards the isolation of bioactive compounds from organisms thriving in these areas remain largely unexplored. Rather, a lot of attention has being focused on the terrestrial environment with most works dedicated to plant secondary metabolites (Adotey et al. 2012; Asomaning et al. 1999). This paper reports on the antimicrobial and antioxidant activities of the crude peptide extracts of two molluscs, Galatea paradoxa (G. paradoxa) and Patella rustica (P. rustica) obtained from the sea and a freshwater in Ghana respectively. G. paradoxa is a bivalve mollusc which belongs to the family Donacidae and is normally constrained to some few rivers in West Africa such as the River Volta in Ghana (Adjei-Boateng et al. 2012; Obirikorang et al. 2013). P. rustica is a gastropod belonging to the family Patellidae and can be found on rocky sea shorelines. Peptides from these two molluscs were extracted and tested against nine pathogenic microbes. The antioxidant activities of these extracts were also investigated. Results and discussion Antimicrobial activity In this work, the crude peptides from G. paradoxa and P. rustica were extracted via cold acetone precipitation. Following lyophilization, the crude peptide extracts were reconstituted in 25 % ACN in 0.1 % TFA and used for the antimicrobial assay. Results are summarized in Table 1. Crude peptide extracts from G. paradoxa was observed to possess a high bactericidal activity with the highest zone of inhibition of 19.5 mm recorded against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Streptococcus pneumoniae and Pseudomonas aeruginosa. E. feacalis exhibited an inhibition zone of 16 mm while Salmonella typhi and Klebseilla pneumoniae recorded 15 mm. Extracts from G. paradoxa however failed to inhibit the growth of the fungus Candida albicans. P. rustica crud (...truncated)