# Anticancer Effects of Seaweed-Derived Bioactive Compounds
## 3 Seaweed Polysaccharide
For instance, fucoidan is a long-chained sulfated polysaccharide that is widely isolated from different seaweed species, such as _Undaria pinnatifida_, _Laminaria japonica_, and _Fucus vesicusus_[18]. In particular, the dry weight of _Sargassum spon_. and _Focus_ sp. contained 8% to 12% fucoidan polysaccharides. The complex sulfated polysaccharides of fucoidan are also composed primarily of sulfated L-fucose and a small amount of glucose, mannose, xylose, and rhamn [19]. Highly sulfated polysaccharide fractions isolated from _Sagassum pallidum_, specifically SP1, SP2, and SP3, showed potent cytotoxic activity in various cancer cell lines, such as A549 (lung adenocarcinoma), HepG2 (hepatocellular carcinoma), and MGC-803 (gastric cancer) cells [20]. The anticancer activities of the SP fractions correlated with sulfate content. These results indicate that the high sulfate content and lower molecular weight of SP are more advantageous for its anticancer activity. Sulfated polysaccharides isolated from _Dicytopteris delicatula_ and _Dicytopteris polyodioides_ exhibited anticancer activity in HeLa (60-70%) and RPMI-7951 (28%) cancer cells [21; 22]. The authors investigated the precise mechanisms underlying these anticancer activities, including tumor angiogenesis, modulation of the immune system, arrest of the cell cycle, and apoptosis [23]. Fucoidan (3) isolated from _Sargassum hornery_, _Eclonia cava_, and _Costaria costata_ also showed anti-tumor potential, inhibiting colony formation in melanoma (SK-MEL-28 cells) and colon cancer cells (DLD-1 cells) [24]. In this report, it was difficult to correlate the chemical structure of fucoidan (3) and its anticancer activity. Several reports indicate that sulfate content is correlated with anticancer activity [25]; however, their results do not show a correlation between chemical structure and activity. [PERSON] and colleagues reported that low- and high-molecular-weight fucoidans isolated from the brown seaweed _Undaria pinnatifida_ were structurally modified by adding a sulfate group synthetically. In stomach AGS cancer cells, the anticancer activity of oversulfated fucoidan was examined. Results showed that a low molecular fraction (<30 kDa) was more potent than the >30 kDa fraction [26]. Fucoidan, laminarin, and alginate (2) isolated from _Coccophora langs-dorfii_ were tested for their anticancer activity against SK-ML-5 and SK-ML-28 melanoma  
Figure 1: Structures of seaweed polysaccharides. cells. The isolated compounds accounted for 28% and 76% of these two melanoma cells, respectively. However, the compounds showed weak activity toward breast cancer cells (MDA-MB-231) [27]. To date, polysaccharides and sulfated polysaccharides have been demonstrated to exhibit significant anticancer activity against various in vitro cancer cell models. Laminarin (**1**) from the _Laminaria difitata_ showed anticancer effects against ovarian cells by inducing apoptosis signaling and endoplasmic reticulum (ER) stress, reactive oxygen species (ROS) generation, and altering the ER-mitochondria axis [28]. Laminarin (**1**) also induced apoptosis via the ErbB signaling pathway in colon cancer cells [29]. In addition, ascophyllan extracted from _Ascophyllum nodosum_ inhibited U937 lymphoma growth by inducing DNA fragmentation and eventually apoptosis.