The green macroalgae, Enteromorpha compressa (Linnaeus) Nees, Ulva lactuca, and E. linza, were seasonally collected from Abu Qir bay at Alexandria (Mediterranean Sea) This work aimed to investigate the seasonal environmental conditions, controlling the green algal growth, predominance, or disappearance and determining antioxidant activity. The freshly collected selected alga (E. compressa) was subjected to pigment analysis (chlorophyll and carotenoids) essential oil and antioxidant enzyme determination (ascorbate oxidase and catalase). The air-dried ground alga was extracted with ethanol (crude extract) then sequentially fractionated by organic solvents of increasing polarity (petroleum ether, chloroform, ethyl acetate, and water). Antioxidant activity of all extracts was assayed using different methods (total antioxidant, DPPH [2, 2 diphenyl-1-picrylhydrazyl], ABTS [2, 2 azino-bis ethylbenzthiazoline-6-sulfonic acid], and reducing power, and β-carotene linoleic acid bleaching methods). The results indicated that the antioxidant activity was concentration and time dependent. Ethyl acetate fraction demonstrated higher antioxidant activity against DPPH method (82.80%) compared to the synthetic standard butylated hydroxyl toluene (BHT, 88.5%). However, the crude ethanolic extract, pet ether, chloroform fractions recorded lower to moderate antioxidant activities (49.0, 66.0, and 78.0%, resp.). Using chromatographic and spectroscopic analyses, an active compound was separated and identified from the promising ethyl acetate fraction.

Background Chlorella vulgaris is a microalga potentially used for pharmaceutical, animal feed, food supplement, aquaculture and cosmetics. The current study aims to study the antioxidant and prooxidant effect of Chlorella vulgaris cultivated under various conc. of copper ions. Methods The axenic green microalgal culture of Chlorella vulgaris was subjected to copper stress conditions (0.00, 0.079, 0.158, 0.316 and 0.632 mg/L). The growth rate was measured at OD680 nm and by dry weight (DW). Moreover, the Antioxidant activity against DPPH and ABTS radical, pigments and phytochemical compounds of the crude extracts (methylene chloride: Methanol, 1:1) were evaluated. The promising Cu crude extract (0.316 mg/L) further fractionated into twenty-one fractions by silica gel column chromatography using hexane, chloroform and ethyl acetate as a mobile phase. Results The obtained results reported that nine out of these fractions exhibited more than 50% antioxidant activity and anticancer activity against Hela cancer cell lines. Based on IC50, fraction No. 7 was found to be the most effective fraction possessing a significant increase in both antioxidant and anticancer potency. Separation of active compound (s) in fraction No 7 was performed using precoated silica gel plates (TLC F254) with ethyl acetate: hexane (9:1 v/v) as mobile phase. Confirmation of active compound separation was achieved by two-dimensional TLC and visualization of the separated compound by UV lamp. The complete identification of the separated active compound was performed by UV- Vis- spectrophotometric absorption, IR, MS, H1-NMRT C13-NMR. The isolated compound ((2E,7R,11R)-3,7,11,15-Tetramethyl-2-hexadecenol) have high antioxidant activity with IC50 (10.59 μg/ml) against DPPH radical assay and comparable to the capacities of the positive controls, Butylated hydroxy toluene [BHT] (IC50 11.2 μg/ml) and Vitamin C (IC50 12.9 μg/ml). Furthermore, pure isolated compound exhibited a potent anticancer activity against Hela cell line with IC50 (4.38 μg/ml) compared to Doxorubicin (DOX) as synthetic drug (13.3 μg/ml). In addition, the interaction of the pure compound with Hela cancer cell line and gene expression were evaluated. Conclusions The authors recommend cultivation of Chlorella vulgaris in large scale under various stress conditions for use the crude extracts and semi purified fractions for making a pharmaco-economic value in Egypt and other countries.

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The aim of this work was to determine the biochemical compounds and evaluate the biological activities of Chlorella vulgaris cultivated under a biotic stress condition (various Zinc and Cupper conc.). The growth rate was recorded as well as determination of active compounds, pigments and defense enzymes, in addition to the biological activities as antioxidant, antimicrobial and anticancer. The obtained results revealed that, higher copper concentrations [0.632 mg /L (Cu)] showed an inhibitory effect to growth while 1.76 mg /L (Zn) enhanced growth which reached its maximum at 25 th day of cultivation. Furthermore, combination of 0.88mg/L (Zn) and 0.316mg /L (Cu) induced an increase in growth rate, catalase, tannins, lipid peroxidation and glutathione-S-transferase and a decrease in flavonoids, phenolic content, protein and antioxidant activity. Also, the results of antioxidant activity showed that, elevation of Zn conc. induced an augmentation of antioxidant activity either by DPPH(2, 2 diphenyl-1-picrylhydrazyl) or ABTS (2, 2'-azino-bis ethylbenzthiazoline-6-sulfonic acid), with maximum activity at 0.88 mg/L Zinc conc. (89.91%) even exceeded those of control (85.62%). While more elevated Zn conc. (1.76 mg/L) induced lower activity when compared with synthetic antioxidant standard (Butylated hydroxyl toluene, BHT). Concerning antimicrobial activity, Gram +ve bacteria, Staphylococcusaureus recorded moderate activity in sulfur-contained extract. Cytotoxicity of three cancer cell lines was inversely proportional to extracts conc. used, where the higher conc. (500µg/ml) showed the lowest cell viability of the tested cell lines which ranged from 22.06 to 69.89%. 0.316 mg/L (Cu) of conc. 500 µg/ml recorded the lowest

The objective of the present study is to determine the antioxidant and anticancer activities of Nostoc linckia extracts cultivated under heavy metal stress conditions (0.44, 0.88, and 1.76 mg/L for zinc and 0.158, 0.316, 0.632 mg/L for copper). Phycobiliprotein, phenolic compounds, flavonoids, and tannins were measured. Active ingredients of extracts were evaluated by GC-mass spectroscopy. The obtained results revealed that higher zinc and copper concentrations showed growth inhibition while 0.22 mg/L (Zn) and 0.079 mg/L (Cu) enhanced growth, reaching its maximum on the 25th day. Increases in catalase, lipids peroxidation, and antioxidants, as well as tannins and flavonoids, have been induced by integration of 0.88 mg/L (Zn) and 0.316 mg/L (Cu). Elevation of Zn concentration induced augmentation of antioxidant activity of crude extract (DPPH or ABTS), with superior activity at 0.44 mg/L zinc concentration (81.22%). The anticancer activity of Nostoc linckia extract (0.44 mg/L Zn) tested against four cancer cell lines: A549, Hela, HCT 116, and MCF-7. The extract at 500 µg/mL appeared the lowest cell viability of tested cell lines. The promising extract (0.44 mg/L Zn) recorded the lowest cell viability of 25.57% in cervical cell line, 29.74% in breast cell line, 33.10% in lung cell line and 34.53% in the colon cell line. The antioxidant active extract showed significant stability against pH with attributed increase in antioxidant activity in the range between 8–12. The extract can be used effectively as a natural antioxidant and anticancer after progressive testing.

The current work aims to investigate the effect of abiotic stresses (nitrogen (N) and sulfur (S) [0.0 g/l, 1.5 g/l, 3 g/l, 6 g/l, and 12 g/l N and 0.0 g/l, 0.07 g/l, 0.15 g/l, 0.3 g/l, and 0.6 g/l S] and their combination [0.3 g/l S + 6 g/l N]) of axenic culture of Nostoc linckia on the production of secondary metabolites which induce different biological activities. Growth rate was measured by dry weight (DW) and optical density (OD) 550 nm . Additionally, phytochemical compounds, defense enzymes as well as antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(ethylbenzthiazoline-6-sulfonic acid) (ABTS ·+ ) radical assays of crude extracts (methylene chloride:methanol, 1:1) were evaluated. Based on antioxidant activity, four promising extracts were subjected to different biological activities such as anticancer, antimicrobial, and antiviral activities. The obtained results revealed that supplementation of external nitrogen source in the form of sodium nitrate was found to increase the total phycobiliprotein content by fivefold. Also, nitrogen depletion provoked significantly highest quantities of phenolic and flavonoid content and this has effects on biological activities of Nostoc linckia . Moreover, 0.3 g/l S was found to be the most effective extract exhibiting a significant increase in antioxidant activity based on DPPH and ABTS assays, respectively (88.18 ± 0.64% and 84.20 ± 1.01%). Furthermore, it recorded anticancer activity against HCT 116 cell line with IC 50 of 155 μg/ml. Moreover, this extract possessed a noticeable antibacterial potency (21.0 ± 1.0 as mm inhibition zone against Staphylococcus aureus and 19.3 ± 0.6 against Streptococcus mutans ). In addition, its antiviral activity against H 5 N 1 virus as a percentage of inhibition was 50% and 63.6% at a concentration of 7 μg/ml and 28 μg/ml, respectively, with cytotoxicity less than 7 μg/μl. GC-MS analysis recorded the presence of bioactive compounds exhibiting different biological activities. Therefore, the obtained results can represent valuable bioactive compounds with variable biological potencies.

In this study, the effects of combined stress factors involving light intensity and salinity (NaCl, MgCl2, CaCl2, and their combinations) on the two-stage cultivation of Chlorella vulgaris for simultaneous production of biomass and high-value products, were investigated. The two-stage strategies comprised a 25-day vegetative stage in BG11 medium, followed by a 15-day combined stress stage. During salt stress conditions, the addition of 15 g L−1 CaCl2 or 7.5 g L−1 MgCl2 / 7.5 g L−1 CaCl2 mixture with 140 µmol m−2 s−1 light intensity significantly promoted the growth of C. vulgaris achieving maximum biomass productivity of 50.50 ± 0.50 and 50.25 ± 3.25 mg L−1 d−1, respectively. Cultivation of C. vulgaris in a medium containing 7.5 g L−1 NaCl/ 7.5 g L−1 CaCl2 had remarkably increased the lipid content (31.15 ± 1.18%) and lipid productivity (14.55 ± 1.48 mg L−1 d−1). The saturated fatty acids (SFAs) at 39.52–59.29%, monounsaturated fatty acids (MUFAs) at 27.16–35.47%, and polyunsaturated fatty acids (PUFAs) at 7.18–29.97%, were obtained with palmitic (C16:0), oleic (C18:1), stearic (C18:0), and linolenic (C18:3) acids as predominant fatty acids. Cultures supplemented with 5 g L−1 NaCl / 5 g L−1 MgCl2 / 5 g L−1 CaCl2 and high light intensity exposure attained consistently high carbohydrate content (52.71 ± 2.50%). The combination of 7.5 g L−1 NaCl / 7.5 g L−1 MgCl2 also resulted in a marked increase in the protein content (35.32 ± 2.20%) and total carotenoids (0.31 ± 0.03 μg mL−1) as compared to the Controls. The highest antioxidant activity (86.16%) was achieved with a 7.5 g L−1 NaCl / 7.5 g L−1 CaCl2 combination in the growth stage. The antioxidant activities were attributed to the presence of phenolics, flavonoids, and tannins due to the stressed conditions. One of the key benefits of using a combined stress strategy in this study is that if one factor has a low impact on enhancing target metabolites, other factors can compensate.