Cytotoxic and anticancer agents in mucus of Galaxea fascicularis: Purification and characterization

Abstract

Various cytotoxic components derived from the mucus of the coral Galaxea fascicularis were investigated. Chromatography of the crude mucus extract through CM-Sepharose separated the components into 15 peaks, nine of which were found to express cytotoxic activity against rat liver cells. Trypan blue dye exclusion assay indicated that peaks P4, P5, and P8b induced the highest level of cytopathy in normal rat liver cells. P4 and P5 contained both protein-aceous and nonproteinaceous components and had heat-labile protease activity. The cytotoxins in P4 and P5 were nonproteinaceous. Further purification of P8b using a normal-phase silica column on HPLC yielded a nonproteinaceous and sugar-rich cytotoxin, S2. Mass spectrometry indicated S2 to be 742 Da in size. On incubation with endo-β-galactosidase, S2 lost more than 50% of its activity, suggesting that its active moiety is glycosylated. Further analysis of the carbohydrate composition revealed that S2 contained an N-linked sialylate glycan chain of NeuNAcα(2-6)Galβ(1-4)GlcNAc. Of the cancer cell lines tested with the mucus components, a vincristine-resistant murine leukemia cell (P388/VCR) was found to be most susceptible, with an LD50 of 0.3 μg/ml, thereby suggesting the potential of this coral mucus as a source of important compounds for anticancer drug screening and development.