Comparative Profiling of Organic Acids, Phenolics, and Tocopherols in Freshwater and Marine Crabs: Effects of Solvent Systems and Habitat

Crabs are shellfish found worldwide, with shells rich in essential macro- and microelements, including potassium, phosphorus, calcium, magnesium, copper, iron, manganese, and zinc. Their shells also contain chitin, chitosan, carotenoids, and selenium, which are reported to have antimicrobial, anticancer, and non-toxic properties. Crab samples were collected from a freshwater river in Mosul, Iraq, and from the Persian Gulf. After washing, cleaning, and removal of internal organs, the samples were dried and sterilized at 150 °C for 2 h, then ground into powder. Extracts were prepared from both freshwater and marine crabs using four solvents in the following sequence: water, methanol, hot water solution, and a methanol-water mixture (1:1, v/v). The yield of the extracts was then comparatively evaluated according to the solvent used. The aim of this study was to identify bioactive components—phenolic compounds, organic acids, and tocopherols—using high-performance liquid chromatography (HPLC). Analyses detected 11 phenolic compounds, nine organic acids, and four tocopherols. The dominant phenolic was p-hydroxybenzoic acid, the primary organic acid was succinic acid, and α-tocopherol was most common in methanol-water extracts. The results highlight that the choice of solvent is crucial for maximizing the extraction of bioactive compounds.