en Biotechnology Biotechnology پژوهشي Orginal research papers <i><span lang="TR" style="font-size:11.0pt"><span style="background:white"><span calibri="" style="font-family:"><span style="color:black">Chlorella</span></span></span></span></i><span lang="TR" style="font-size:11.0pt"><span style="background:white"><span calibri="" style="font-family:"><span style="color:black">, a green microalga, is valued in food and medicine for its high nutritional and functional properties. Reactive oxygen species can cause oxidation reactions linked to cardiovascular diseases, degenerative conditions, and cancer. However, bioactive compounds and carotenoids in microalgae can help to alleviate certain disease symptoms by protecting tissues. Polysaccharides from <i>C. vulgaris</i> were extracted using a hot water method and their antioxidant activity was evaluated through the DPPH radical scavenging method and reducing power. The impact on the death rate of mouse colon cancer cells (CT-26) was also assessed using the 2, 5-diphenyl-2H-tetrazolium bromide (MTT) method. The analysis showed that <i>C. vulgaris</i> contained 19.08&plusmn;0.09 w/v % polysaccharides and yielded about 5% of its dry weight. The extracted polysaccharides demonstrated antioxidant activity with the highest DPPH inhibition and reducing power, measuring 91.15% and 0.781% at 6 mg/mL, respectively. BHA at 0.031 mg/mL exhibited DPPH scavenging (39.78%) and reduced the power (3.65%). The polysaccharides also showed cytotoxic effects, specifically against CT-26 cells with an IC50 value of 481.53&mu;g/mL after 48 h. These findings suggest that polysaccharides from <i>C. vulgaris</i> may possess potential cytotoxic properties against tumor cell lines.</span></span></span></span> Cytotoxicity, Polysaccharides, Chlorella vulgaris, Biochemical compounds 969 981 http://jifro.ir/browse.php?a_code=A-10-4108-2&slc_lang=en&sid=1 Z. Yaghoubzadeh za_yaghoub@yahoo.com 100319475328460056875 100319475328460056875 Yes Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO) R. Safari safari1353@gmail.com 100319475328460056876 100319475328460056876 No Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO)