Fish lipids have aroused intensive clinical interest due to the pharmacological activities against various diseases, the consumption of which prevents human chronic inflammatory, cardiovascular diseases and cancer. Although studies have been devoted to analyzing and explaining the role of fish lipids against various degenerative diseases, further studies are still needed and the types of fishes involved remain limited.
Silver carp (Hypophthalmichthys molitrix), as one of the main freshwater fish species in China, contributes 3,713,922 tons in 2011. However, over half of total fishery products are being discarded as inedible by-products every year. Traditionally considered physically and intelligently nutritious and beneficial, fish brain, as a derivative though, is popular in China and is thus of industrial interest nowadays. The advantages of fish brain stem from the high content and quality of lipids which, however, has seldom been accessed regarding health issues.
Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphocholine), which is key in atherosclerosis development, is also an extremely potent aggregating agent participating in the inflammatory development of plaque and the blockage of blood vessels that finally lead to coronary heart disease. Many foodstuffs contain molecules that inhibit the activity of PAF as PAF antagonists that are nutritionally valuable because they prevent platelets aggregation in arteries and atheromatosis generation simultaneously. Previous researches have revealed that lipids extracted from wild haddock and coley exhibited PAF-inhibiting activities.
Many foods primarily deteriorate because of microbes that give rise to the loss of quality and safety, on which people worldwide are concerning more because foodborne diseases are subject to outbreak due to pathogenic and spoilage microorganisms in foods. In addition, both Gram-positive and Gram-negative bacteria evoke a state of shock that is characterized by cardiovascular collapse. Numerous bacteria are able to produce PAF. For instance, PAF can be synthesized by being stimulated with Staphylococcus aureus toxins or it can be released by Escherichia coli. Given that PAF is an initial trigger in atherosclerosis, foodstuffs, which exert antibacterial activities, suppress the production of PAF, and therefore play a positive role in preventing atherosclerosis. Previous studies have demonstrated the lipids extracted from red shrimp brain, marine sponge, sea bass and gilthead sea bream exerted antibacterial activities[10, 12, 13]. Besides, antimicrobial agents have been prepared from the lipids of marine fishes.
Free radicals are engaged in the development of cardiovascular disease, cancer, liver disease and other chronic and inflammatory diseases based on oxidative damages, the scavenging of which therefore has been spotlighted. It has previously been reported that smokers displayed enhanced antioxidant capacity after being administered with fish oil which is associated with the reduced susceptibility of myocytes to injury-inducing reactive oxygen species upon dietary supplementation.
In the present study, the lipid fractions of silver carp brain were tested for their biological activities concerning platelet aggregation induction or PAF-induced platelet aggregation inhibition. The antibacterial activities of the lipids against E. coli, S. aureus, Shigella dysenteriae, Salmonella typhi and Listeria monocytogenes were examined. Moreover, their radical-scavenging effects were determined by utilizing 2,2-diphenyl-1-picrylhydrazyl (DPPH). The results may assist to explain the pharmacological activities of fish lipids against various diseases. Furthermore, the results may shed light on the commercial and industrial utilization of silver carp brain lipids as eligible bioactive ones.