Characteristics of Polyphenolic Content in Brown Algae of the Pacific Coast of Russia

Water and ethanol brown macroalgal extracts of nine species of Laminariales and four species of Fucales of the Pacific coast of Russia were investigated. It has been shown that brown algae species of Agarum, Thalassiophyllum, Fucus and Cystoseira can be a source of the polyphenolic compounds with antioxidant activity. Phenolic content in the ethanol algal extracts (Undaria pinnatifida, Arthrothamnus bifidus, Thalassiophyllum clathrus and Agarum turneri) was 1.1–3.5 times higher than in the water extracts. In Sargassum pallidum and Kjellmaniella crassifolia, the total polyphenolic content was 2.1 and 1.6 times higher, respectively, in water extracts than in ethanol extracts. The maximum radical scavenging activity has been detected in Agarum turneri ethanol extracts (38.8 mg ascorbic acid/g and 2506.8 µmol Trolox equiv/g dry algae). Phlorotannin content varies from 16.8 μg/g dry sample of Costaria costata to 2763.2 μg/g dry sample of Agarum turneri. It is found the content of polyphenolic compounds in brown algae is determined mainly by their species-specificity and by their belonging to the genus. The presence of major phenols in the extract of Thalassiophyllum clathrus, such as phenolic acid (gallic acid), hydroxycinnamic acids (caffeic acid, chlorogenic acid, coumaric acid) and flavonols (kaempferol, quercetin) has been established.

In Vitro Anticancer and Radiosensitizing Activities of Phlorethols from the Brown Alga Costaria costata

The anticancer and radiosensitizing effects of high-molecular-weight phlorethols CcPh (Mw = 2520 Da) isolated from the brown algae of Costaria costata on human colorectal carcinoma HCT 116 and HT-29 cells were investigated. Phlorethols CcPh possessed cytotoxic activity against HT-29 (IC50 = 92 μg/mL) and HCT 116 (IC50 = 94 μg/mL) cells. CcPh at non-toxic concentrations inhibited the colony formation in colon cancer cells and significantly enhanced their sensitivity to low non-toxic X-ray irradiation. The combinatory effect of radiation and CcPh was synergistic (Combination index < 0.7). Algal phlorethols might be prospective candidates as radiosensitizers to improve the scheme of radiotherapy.