Porphyridium aerugineum is a unicellular freshwater red microalga that synthesizes and secretes into the culture medium an extracellular polysaccharide (EPS). In this study, algal growth and polysaccharide production, as well as the antioxidant capacity and antitumor effect of Porphyridium aerugineum EPS (PaEPS), were investigated. Cultivation of the microalgae was carried out in a photobioreactor under controlled conditions. Algal growth and the amount of EPS were monitored daily. The accumulated polysaccharide was extracted and lyophilized. At the end of cultivation, the concentration of microalgal biomass and PaEPS reached 3.3 and 1.2 g L⁻¹, respectively. To examine the antioxidant capacity of PaEPS, FRAP and ABTS assays were performed. The cytotoxic activity of PaEPS was evaluated on the tumor cell lines MCF-7 (breast cancer) and HeLa (cervical adenocarcinoma) and on BJ (a non-tumor human skin fibroblast cell line), using MTT assay. The results obtained indicated that P. aerugineum polysaccharide exhibited a high ABTS radical-scavenging activity reaching up to 55%. The cytotoxic effect was best expressed in MCF-7 cells treated for 72 h with 1000 µg/mL PaEPS, where tumor cell proliferation was inhibited by more than 70%. Importantly, the PaEPS treatments did not significantly affect the viability of BJ cells. These findings promote the biotechnological production of P. aerugineum extracellular polysaccharide and reveal its potential as an anticancer and antioxidant agent for future applications.

Algal metabolites have been extensively studied as potential anticancer therapeutics. Among them, polysaccharides have attracted much attention because of their beneficial biological effects and safety. In the present research, the chemical characteristics, antitumor, and proapoptotic activities of extracellular polysaccharides (EPS) isolated from a new Bulgarian strain of the green microalga Coelastrella sp. BGV were investigated. A fast and convenient method of precipitation with cold ethanol was used to isolate EPS from the culture medium. The chemical characteristics of the isolated EPS were examined by colorimetric and spectrophotometric analyses, HPSEC-RID and HPLC-UV chromatography, and FT-IR spectroscopy. The results showed that the isolated EPS sample consists of three carbohydrate fractions with different molecular weights (11.5 × 10⁴ Da, 30.7 × 10⁴ Da, and 72.4 × 10⁴ Da, respectively) and contains 7.14 (w/w%) protein. HPLC-UV analysis revealed the presence of galactose and fucose. The total uronic acid content in the sample was 4.5 (w/w%). The IR-FT spectrum of EPS revealed the presence of various functional groups typical of a polysaccharide (or proteoglycan) composed primarily of neutral sugars. The anticancer potential of the obtained EPS was assessed using cell lines with cancerous and non-cancerous origins as in vitro experimental models. The results of the performed MTT assay showed that EPS reduced the viability of the cervical and mammary carcinoma cell lines HeLa and MCF-7, while the control non-cancer cell lines BALB/3T3 and HaCaT were less affected. The HeLa cell line showed the highest sensitivity to the effects of EPS and was therefore used for further studies of its anticancer potential. The ability of EPS to inhibit cancer cell migration was demonstrated by wound-healing (scratch) assay. The cell cycle FACS analysis indicated that the EPS treatment induced significant increases in the sub G1 cell population and decreases of the percentages of cells in the G1, S, and G2-M phases, compared to the control. The fluorescent microscopy studies performed using three different staining methods in combination with Annexin V-FITC flow cytometric analysis clearly demonstrate the ability of EPS to induce cancer cell death via the apoptosis pathway. Moreover, an altered pattern and intensity of the immunocytochemical staining for the apoptosis- and proliferation-related proteins p53, bcl2, and Ki67 was detected in EPS-treated HeLa cancer cells as compared to the untreated controls. The obtained results characterize the new local strain of green microalgae Coelastrella sp. BGV as a producer of EPS with selective antitumor activity and provide an opportunity for further studies of its pharmacological and biotechnological potential.

Green algae of the genus Coelastrella have attracted the attention of scientists due to their rich biochemical composition and potential for application in phytomedicine. The present study investigated the influence of light on the bioactive capacity of extracts from the Bulgarian strain of the green microalgae Coelastrella sp. BGV. Three LED lights were examined—red/blue (C1), blue (C2), and control white light (C3). The respective ethanol extracts were analyzed for the total content of phenolic antioxidants. The antimicrobial activity was tested using the disk-diffusion method against 10 microorganisms. The antiproliferative and cytotoxic effects on cervical carcinoma HeLa and hepatocellular carcinoma HepG2 cell lines, as well as non-tumorigenic embryonal fibroblasts BALB/3T3 control, were evaluated using a cell viability assay. The overall results highlighted blue light as a factor enhancing the antioxidant, antibacterial, and cytotoxic activities of the C2 microalgal extract. Additionally, the investigated mechanism of the antitumor activity revealed a proapoptotic effect. In contrast, the C1 extract exhibited weaker activity and selectivity, while the C3 extract was the least active but demonstrated high cytotoxic selectivity. This study could contribute to expanding knowledge about the high biological potential of green microalgae and the development of biotechnological approaches for its regulation.

Microalgae are of great importance for the production of original natural substances of interest for food, health or biotechnological applications. Mass cultures of green microalgae are used for production of carotenoids such β-carotene, astaxanthin, canthaxanthin, lutein etc. The aim of this study was to obtain an oil extract from a Bulgarian green microalga strain Coelastrella sp. BGV and to assess its anticancer and apoptogenic activity in vitro against human tumor cells HeLa by means of MTT and fluorescence microscopy analyses. The results showed that the oil extract obtained by a direct extraction using a common vegetable oil reduces proliferation and induces apoptosis in HeLa cells. In contrast to widely used organic solvents for the production of carotenoids, the applied bio-solvent (sunflower oil) can be a valuable alternative approach for the needs of the food industry. The resulting oil extract showed promising antitumor and apoptosis-inducing activity against HeLa cells in vitro and potential for future use in practice.

Clinopodium vulgare L. is a valuable medicinal plant with various beneficial effects on health. In this study, water extracts from the aerial part of the wild and in vitro cultured C. vulgare plants were obtained. The polyphenol, flavonoid content and antioxidant activity of the extracts as well as their antitumor efficiency against a panel of cell lines were analyzed. The ability of C. vulgare to inhibit cancer cell migration and induce apoptosis in the tumor cells was examined by wound healing assay and fluorescence microscopic methods. The effect of the extracts on the cell cycle progression of the tumor cells was analyzed by flow cytometry. The presented results show that the antitumor activity of the extracts from in vitro cultured plants was similar to and even exceeded that of the wild plants. The cell viability and migration assays demonstrate the selective anticancer effect of the extract and significant inhibition of cancer cell proliferation and motility. The fluorescence microscopy and cell cycle analyses indicate that the antitumor activity of the in vitro plant extract was related to both antiproliferative and proapoptotic effects. These results show that C. vulgare plants obtained by in vitro micropropagation and cultivated ex vitro are promising candidates for anticancer drug therapy.