## 3 Metabolomics Applied to Marine Organisms in Cancer Studies
### Structure Elucidation of Bioactive Molecules from Algae
It is worth observing that the particular attention paid to some brown algae is due to the production and storage of a sulphated polysaccharide called Fucoidan, which is well known as a promising compound to be applied for cancer treatment. Among various species of brown algae, one of the best known is _Cladosiphon okamurans_, an edible alga that is commonly cultured in Japan. This alga largely produces an accessory pigment named fucoxanthin, which is mainly metabolised and transformed into fucoxanthin by the digestive enzymes of the gastrointestinal tracts of consumers. Both compounds are well known and studied because they exert an anti-proliferative effect [118]. [PERSON] et al. [119] extracted fucoxanthin and fucoxanthinol by the seaweed _C. okamuranus_ using HPLC and MS. The results showed potentially anti-osteosarcoma properties, which appear to be at least partially attributable to the inhibition of Akt and AP-1 signal pathwaysin human and mouse osteosarcoma cancer cell lines (Saos-2, MNNG/HOS, 143B and LM8). In addition, various sulphated compounds extracted from algal biomasses have aroused interest for their biotechnological applications. In particular, [PERSON] et al. [120] demonstrated the activity of three sulphated polysaccharides extracted by _U. fascita_ (UFP), _Gloiopeltis funcata_ (GFP) and _Sargassum henslouianum_ (SHP). The polysaccharides were extracted after ultrasonic disruption applying Radial Flow Chromatography (RFC) separation and then tested on MKN45 (gastric cancer) and DLD (intestinal cancer) cell lines. After incubating with those three extracts for 24 h at different concentrations (from 0.125 to 1.00 mg/mL), the inhibitive effects on MKN45 cancer cells were observed. In particular, SHP exhibited the strongest cytotoxic effect, with a growth inhibition percentage of almost 50% at the concentration of 1.00 mg/mL. In contrast, all samples showed low percentages of growth inhibition on DLD cancer cells, at all concentrations. After the aforementioned works, dealing with various macroalgae, hereafter we explore studies focused on the use of microalgae as a source of anti-cancer compounds. The study of [PERSON] et al. [121] investigated the effectiveness of \({}^{1}\)H-NMR and MS metabolomic approaches to record the variation of metabolites naturally present in the dinoflagellate _Amphidinium carterae_ in a long-term culture. Specifically, among other compounds of interest, as fatty acids and carotenoids, they focused on the amphidinol family and their content variation in relationship to different levels of daily irradiance and nutrients in anf/2 medium. Three concentrations of methanolic extract (10, 30, and 100 ug/mL) were tested on four cancer cell lines: namely A549, HT29, MDA-MB-231 and PSN-1, showing a high antiproliferative activity against all four tumor cell lines (80%). Similarly, other studies investigated the chemical composition of the extracts of various microalgae along with their anticancer effects. [PERSON] et al. [122] analysed a crude extract of _Isochrysis galbana_ through \({}^{1}\)H-NMR and GC-MS and tested its cytotoxic effect on four cell lines: chronic myelogenous leukemia K562, human acute T lymphoblastic leukaemia MOLT-4, human Caucasian histiocytic lymphoma U937, Caucasian promylocytic leukemia HL60 and human Burkitt's lymphoma Raji cancer cells, showing the highest cytotoxicity (about 24.07%) at a concentration of 500 ug/mL against Raji cells. An interesting approach to the assay of natural products against cancer cell lines was reported by [PERSON] et al. [123]. They tested crude extracts of two microalgae (_Chlorella protthecoides_ and _Nannochloropsis oculata_) against A172 (brain glioblastoma) and HCT116 cell lines.