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Crabs of the genus Charybdis are some of the world’s most aggressive and voracious marine invasive crustaceans. They are found in a wide variety of ecosystems in the Red Sea. Their near ubiquity in diverse marine habitats, however, makes them a possible resource for novel marine-derived bioactive products. To provide an important insight into the potential for C. natator as a beneficial product, its shell methanolic extract was chromatographically analyzed for identification of potential bioactive ingredients. Additionally, two different doses, i.e. a low and a high dose, of this extract were tested for their ability to protect against copper-induced oxidative stress and proinflammatory response in adult zebrafish Danio rerio. Gene expression levels of transcripts of proinflammatory mediators, i.e. nf-κβ and tnf-α; antioxidant enzymes, i.e. sod, cat, and gpx; and lipid-metabolizing enzymes, i.e., acox1 and fasn, were determined. The results showed that C. natator shell is rich in potential bioactive metabolites, including diverse unsaturated fatty acids, alkanes, flavonoids, and phenolic acids. Most antioxidant and proinflammatory transcripts in the protected groups were restored to levels that were lower than those in the CuSO4-stressed group. The low dose showed special success in inducing these effects. Also, the low-dose-protected group showed significantly elevated acox1 and decreased fasn, suggesting the capability of crab shell extract at a low dose to assist lipolysis and inhibit lipogenesis. The abundant presence of saturated fatty acids in the shell extract can be the reason for the inadequacy of the high dose to promote the antioxidant and anti-inflammatory activities. These results suggest that there is a potential to develop therapeutic industrial uses for C. natator shell, instead of considering it as a discard. Its wealth of bioactive metabolites may contribute to the market for natural products to combat inflammatory and oxidative stress, the origin of many diseases in the modern world. [ABSTRACT FROM AUTHOR]

Red Sea organisms represent key and genuine resources for biologically active metabolites. To provide preliminary clues about the biological activities of some Red Sea invertebrates, the soft coral Sarcophyton convolutum and the crab Charybdis natator were obtained. The whole amount of the coral and the shell part of the crab were subjected to extraction to obtain bioactive metabolites. These metabolites were determined in the extracts using Gas chromatography-mass spectrometry (GC-MS). Next, zebrafish protected with these extracts were challenged with copper sulfate (CuSO4) to identify the status of total antioxidant activity in fish livers. The liver was chosen as the main organ where detoxifying and antioxidant enzymes are expressed, as reported in zebrafish and many other fish species before. The results showed that both invertebrate species possess a diverse array of biologically active ingredients, mainly fatty acids, steroid derivatives, flavonoids, sesquiterpenoids, and thiols. The main compounds found in the crab extract were 1-Heptatriacotanol, Dotriacontane, Ethyl iso-allocholate, tert-Hexadecanethiol, 11-Octadecenoic acid, Hexadecanoic acid, and Tetradecane. The analyzed fraction of soft coral extract contained mainly palmitic acid, Isochiapin B, Isooleic acid, and 7,9-Di-tert-butyl-1-oxaspiro(4,5)dec a-6,9-diene-2,8-dione. Zebrafish protected using these extracts showed differential responses. Whereas coral extract could restore the levels of Hydrogen Peroxide (H2O2) scavenging activity to levels that were similar to the negative control group, the crab shell extract seemed to have lesser effects on the same parameter. More work is recommended regarding the in-depth characterization of bioactive ingredients of these organisms using bigger fractions and also to assess further biological activities of them. [ABSTRACT FROM AUTHOR]