Antibacterial Properties of Marine Sponges from Mauritius Waters

Purpose: To investigate the antimicrobial activity of crude and fractionated extracts of Biemna tubulosa and Stylissa spp. thriving in Trou aux Biches lagoon, North East Mauritius.Methods: Crude extracts (methanol: dichloromethane 1:1) and fractions of Biemna tubulosa and Stylissa spp (hexane, ethyl acetate and butanol) were tested against some bacterial organisms, namely, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis, using broth microdilution assay. The extracts were screened for the presence of compounds that could be responsible for bioactivity.Results: Preliminary chemical screening revealed the presence of tannins, saponins, terpenes, alkaloids and phenols. The hexane fraction of Stylissa spp. and the ethyl actetate and butanol extracts of Biemna tubulosa were more active than the control antibiotic. Maximum antimicrobial activity was noted for the butanol fraction of Biemna tubulosa with minimum inhibitory concentration (MIC) of 0.091 mg/ml against E. coli. The hexane soluble fraction of Stylissa spp. was more active with MIC of 0.125 mg/ml against S. aureus and E. coli and 0.250 mg/ml against E. faecalis.Conclusion: The broad spectrum antibacterial activity of these sponges seemed to be due to the presence of sesterterpenes and triterpenes, alkaloids and tannins detected in the extract fractions. This is probably the first report on the antimicrobial activity of Biemna tubulosa and Stylissa spp. from Mauritius waters.Keywords: Biemna tubulosa, Stylissa spp., Antibacterial activity, Marine sponges, MIC

Antibacterial and antibiotic potentiating activities of tropical marine sponge extracts

Increasing prevalence of antibiotic resistance has led research to focus on discovering new antimicrobial agents derived from the marine biome. Although ample studies have investigated sponges for their bioactive metabolites with promising prospects in drug discovery, the potentiating effects of sponge extracts on antibiotics still remains to be expounded. The present study aimed to investigate the antibacterial capacity of seven tropical sponges collected from Mauritian waters and their modulatory effect in association with three conventional antibiotics namely chloramphenicol, ampicillin and tetracycline. Disc diffusion assay was used to determine the inhibition zone diameter (IZD) of the sponge total crude extracts (CE), hexane (HF), ethyl acetate (EAF) and aqueous (AF) fractions against nine standard bacterial isolates whereas broth microdilution method was used to determine their minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs) and antibiotic potentiating activity of the most active sponge extract. MIC values of the sponge extracts ranged from 0.039 to 1.25 mg/mL. Extracts from Neopetrosia exigua rich in beta-sitosterol and cholesterol displayed the widest activity spectrum against the 9 tested bacterial isolates whilst the best antibacterial profile was observed by its EAF particularly against Staphylococcus aureus and Bacillus cereus with MIC and MBC values of 0.039 mg/mL and 0.078 mg/mL, respectively. The greatest antibiotic potentiating effect was obtained with the EAF of N. exigua (MIC/2) and ampicillin combination against S. aureus. These findings suggest that the antibacterial properties of the tested marine sponge extracts may provide an alternative and complementary strategy to manage bacterial infections

Mauritian Endemic Medicinal Plant Extracts Induce G2/M Phase Cell Cycle Arrest and Growth Inhibition of Oesophageal Squamous Cell Carcinoma in Vitro

Terrestrial plants have contributed massively to the development of modern oncologic drugs. Despite the wide acceptance of Mauritian endemic flowering plants in traditional medicine, scientific evidence of their chemotherapeutic potential is lacking. This study aimed to evaluate the in vitro tumor cytotoxicity of leaf extracts from five Mauritian endemic medicinal plants, namely Acalypha integrifolia Willd (Euphorbiaceae), Labourdonnaisia glauca Bojer (Sapotaceae), Dombeya acutangula Cav. subsp. rosea Friedmann (Malvaceae), Gaertnera psychotrioides (DC.) Baker (Rubiaceae), and Eugenia tinifolia Lam (Myrtaceae). The cytotoxicities of the extracts were determined against six human cancer cell lines, including cervical adenocarcinoma, colorectal carcinoma, oesophageal adenocarcinoma, and oesophageal squamous cell carcinoma. The potent extracts were further investigated using cell cycle analysis and reverse phase protein array (RPPA) analysis. The antioxidant properties and polyphenolic profile of the potent extracts were also evaluated. Gas chromatography mass spectrometry (GC-MS) analyses revealed the presence of (+)-catechin and gallocatechin in E. tinifolia and L. glauca, while gallic acid was detected in A. integrifolia. L. glauca, A. integrifolia, and E. tinifolia were highly selective towards human oesophageal squamous cell carcinoma (KYSE-30) cells. L. glauca and E. tinifolia arrested KYSE30 cells in the G2/M phase, in a concentration-dependent manner. RPPA analysis indicated that the extracts may partly exert their tumor growth-inhibitory activity by upregulating the intracellular level of 5′AMP-activated kinase (AMPK). The findings highlight the potent antiproliferative activity of three Mauritian endemic leaf extracts against oesophageal squamous cell carcinoma and calls for further investigation into their chemotherapeutic application

Target analysis for the adipokinetic hormone of 'Daphnia'

Members of the red pigment-concentrating hormone (RPCH)/adipokinetic hormone (AKH) peptide family are involved in many physiological, developmental and behavioral processes in insects, and pigment translocation in decapod crustaceans. In the branchiopod Daphnia pulex, a preprohormone for RPCH/AKH is encoded in the genome and the mature peptide, Dappu-RPCH (pQVNFSTSW-amide) is predicted from the preprohormone. Here, we have developed a method to measure the peptide in hemolymph of Daphnia. It uses reversed-phase liquid chromatography and high-resolution mass spectrometry of the singly- and the doubly-charged peptide ions, respectively, and their gas phase fragmentation for target identification. Pilot studies were conducted with synthetic Dappu-RPCH and the method was sensitive at the low fmol level without biological matrix. When hemolymph samples were however spiked with known amounts of the synthetic peptide, much less peptide was recovered and detected. Thus far, with our method of peptide purification, the endogenous peptide was not detectable in hemolymph of Daphnia where AKH titres of 1 fmol/µl hemolymph are expected.Die Mitglieder der Familie des rotes-Pigment-konzentrierenden (RPCH) / adipokinetischen Hormons sind in viele physiologische und Verhaltens-Prozesse von Insekten sowie die Pigment-Translokation in Zehnfußkrebsen involviert. Im Genom des Kiemenfußkrebses Daphnia pulex ist ein Preprohormon für RPCH/AKH kodiert, nach dem das voll ausgebildete Peptid, Dappu-RPCH (pQVNFSTSW-amide), vorausgesagt wird. Wir haben eine Methode entwickelt, um das Peptid in der Hämolymphe von Daphnia nachzuweisen. Sie verwendet Umkehrphasen-Flüssigchromatographie und hochauflösende Massenspektrometrie des einfach und des zweifach geladenen Peptidions und deren Gasphasenfragmentierung zur Target-Identifizierung. Pilotstudien wurden mit synthetischem Dappu-RPCH durchgeführt. Die Methode war empfindlich auf dem niedrigen fmol-Level ohne biologische Matrix. Wurde jedoch die Hämolymphe mit bekannten Mengen des synthetischen Peptids versetzt, wurde viel weniger Peptid gemessen. Mit unserer bisherigen Methode zur Peptidreinigung konnte daher noch kein endogenes Peptid in der Hämolymphe von Daphnia bestimmt werden, wo AKH-Titer von 1 fmol/µl erwartet werden