In vitro antioxidant, antibacterial, cytotoxic, and epigenetic screening of crude extract and fractions of the marine sponge Neopetrosia exigua from Mauritius waters

Abstract

The marine sponge Neopetrosia exigua is known as a goldmine of novel compounds, yet its pharmacological activities remain poorly characterised. Herein, this study investigates the bioactivities of N. exigua collected from Mauritius waters. The crude extract (dichloromethane: methanol), hexane, ethyl acetate and aqueous fractions obtained from N. exigua were subjected to in vitro antioxidant assays. Their antibacterial activities were evaluated using the broth microdilution method to determine the minimum inhibitory concentration (MIC). The cytotoxic and epigenetic activities were further screened using the MTT assay and a cell-based image system that measures de-repression of a silenced Green Fluorescent Protein (GFP) reporter gene, respectively. Higher antioxidant activity was recorded for the ethyl acetate fraction as demonstrated by its significant ferric reducing antioxidant power, radical scavenging, and metal chelating activities relative to control (p < 0.05). The best antibacterial profile was presented by the ethyl acetate fraction against Cutibacterium acnes (MIC: 0.039 mg/ml), Streptococcus mutans (MIC: 0.078 mg/ml) and Mycobacterium smegmatis (MIC: 0.313 mg/ml). Similarly, the fraction displayed significant cytotoxicity against the human liposarcoma SW872 cells with IC50 value of 44.34 ± 2.64 µg/ml and GFP re-activation capacity of 43.79 ± 3.19% (p < 0.05). This work conveys interesting data on the antioxidant, antimicrobial, and anticancer properties of N. exigua. In particular, this study indicates the promising potential of N. exigua as a reservoir of epigenetically active agents that can modulate transcription of silenced genes involved in carcinogenesis. Hence, further investigations to isolate the active constituents is actively warranted.