Study of antimicrobial, antioxidant and chromatographic profiling of gills and carapaces extracts of mud crab, scylla serrata

This research focused on screening for antimicrobial and antioxidant activities from S.serrata gills and carapaces. The experimental steps started with tissue extraction in ethyl acetate and water. The extracts were subsequently assayed for antimicrobial properties toward human pathogenic bacteria and yeasts. Whereas for antioxidant property, the extracts were tested with ABTS, DPPH and FRAP scavenging activity assays. The chemical profile and toxicity of each extract was also determined. For the result, in antimicrobial assays, there was no activity recorded in all eight extracts on selected human pathogenic microbes. Whereas for antioxidant activity, aqueous extracts showed significant degree of antioxidant activity in ABTS (IC50 of 111.93 to 975.78
µg/ml), DPPH (IC100 of 3336.50 to 3913.39 µg/ml) and FRAP assays [91.57 to 171.65 TE (mg of Trolox/mg of extract)]. For stability test, all extracts showed slight decrement of antioxidant activity at temperature higher than 80°C, with 1.56% to 15.06% decrement. While for pH stability, all extracts showed significant decrement of antioxidant activity as the pH dropped lower than pH 7. In TPC, aqueous extracts showed significant amount of phenolic content with 51.00 to 58.84 GE (mg of gallic acid/mg of extract), compared to ethyl acetate extracts with 15.54 to 47.41 GE (mg of gallic acid/mg of extract).In protein content assay, ethyl acetate extracts were determined with considerably higher protein contents than the protein content of aqueous extracts. In chromatographic profiling with TLC analysis, the absence of flavonoid was confirmed in all S.serrata extracts. In iodine staining, ethyl acetate extracts were determined with three to four major organic components, while aqueous extracts were observed with two major organic components. Whereas in HPLC analysis, the presence of astaxanthin, a xanthophyll carotenoid, was confirmed in all four aqueous S.serrata extracts. Gills extract were recorded with slightly higher content of astaxanthin, compared to carapace extracts. Lastly for BSLT, all aqueous extracts were determined to be non-toxic (LC50 of 1219.93 to 2797.96 µg/ml) while ethyl acetate gills extract were determined to be toxic (LC50 642.00 to 886.36 µg/ml). As a conclusion, this research concluded that S.serrata gills and carapace extracts carry promising potential of antioxidant property, with notable stability toward heat exposure. Unfortunately, both extracts do not contain antimicrobial property toward selected human pathogenic microbes.