Dose-dependent selective cytotoxicity of extracts from marine green alga, Cladophoropsis vaucheriaeformis, against mouse leukemia L1210 cells

Phytochemical screening, antioxidant potential, and cytotoxic effects of different extracts of red algae (Laurencia snyderiae) on HT29 cells

Background and purpose

Marine algae are potential renewable and sustainable sources of bioactive natural products which can be utilized in nutraceutical and pharmaceutical industries.

Experimental approach

Different extracts (methanol, chloroform, and ethyl acetate) of red algae, Laurencia snyderiae, was evaluated for their antioxidant potential, with various antioxidant assessment assays, cytotoxic properties (using MTT colorimetric assay), and phytochemical constituents (total phenolic and flavonoid contents). The GC-MS analyses of the algal methanolic extract and its apoptotic effects on the human colon carcinoma cell line (HT29) were also investigated.

Findings/Results

The total phenolic content in the methanol, chloroform, and ethyl acetate extracts of L. snyderiae was 3.6 ± 0.12, 3.2 ± 0.41, and 3.3 ± 0.35 μg/mg of gallic acid, respectively. Among different algae extracts, chloroform extract showed significantly chelating ability (IC₅₀ = 0.027 mg/mL) and reducing power activity (IC₅₀ = 0.082 mg/mL), while the highest DPPH scavenging activity (IC₅₀ = 0.058 mg/mL) exhibited in the methanol extract compared to the other extracts. The methanolic extract was found to have a higher cytotoxicity effect on colon carcinoma cells with IC₅₀ 70.2 μg/mL. The viability of the cancer cells was increased with the decrease in the concentration in different extracts. GC-MS analysis of the algal methanolic extract revealed the presence of active antitumor constituents and apoptosis-based cytotoxicity against colon cancer cells through the DNA damage was also confirmed.

Conclusion and implications

Based on these results, the red algae L. snyderiae possesses potent bioactive constituents and can use as additional resources as a natural antioxidant and antitumor agent in the pharmaceutical and nutraceutical area.

Acetylenic Aquatic Anticancer Agents and Related Compounds

Although acetylenes are common as components of terrestrial plants, it is only within the last 30 years that biologically active polyacetylenes having unusual structural features have been reported from aquatic organisms: cyanobacteria, algae, fungi, invertebrates, and other sources. Naturally occurring aquatic acetylenes are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifouling, antifungal, pesticidal, phototoxic, HIV inhibitory, and immuno-suppressive properties. There is no doubt that they are of great interest, especially for the medicinal and/or pharmaceutical industries. This review presents structures and describes cytotoxic and anticancer activities of more than 230 acetylenic metabolites isolated from aquatic organisms. With the computer program PASS some additional biological activities are also predicted, which point toward possible new applications of these compounds. This review emphasizes the role of aquatic acetylenic compounds as an important source of leads for drug discovery.

The evaluation of the genotoxic and oxidative damage potentials of Ulothrix tenuissima (Kutz.) in vitro

Several alga species are known to produce a variety of toxic metabolites that pose a threat to aquatic organisms, animals and humans. Moreover, these metabolites have been thought to cause serious diseases including certain cancers and neurodegenerative disorders. On the other hand, Ulothrix is a genus of filamentous green algae, generally found in fresh water and marine and abundantly available in some lakes and rivers of Turkey. To our best knowledge, no study has been performed to assess the genotoxic and biochemical effects of U. tenuissima on cultured human blood cells. Therefore, in order to determine clastogenic or aneugenic effects of aqueous alga extracts the micronucleus assay was carried out. Nuclear division index (NDI) in peripheral lymphocytes was also analyzed for cytotoxicity evaluations. In addition, biochemical parameters (total antioxidant capacity (TAC) and total oxidative stress (TOS)) were examined to determine oxidative effects. For this aim, we obtained heparinized blood samples from three healthy persons. The alga samples were collected from Porsuk Pond in Hasankale (Erzurum, Turkey) in summer period of the year 2010. The aqueous extracts of this species were added to cultures at different concentrations (0 to 5000 ppm) for 72 h. Our results showed that this alga did not cause any statistically important changes in the rates of studied genotoxicity endpoint. But dose-dependent alterations were observed in TAC and TOS levels and NDI rates. In conclusion, U. tenuissima was found to be non-genotoxic but caused sterility at higher concentrations due to oxidative stress.

The novel anti-Propionibacterium acnes compound, Sargafuran, found in the marine brown alga Sargassum macrocarpum

We screened extracts of 342 species of marine algae collected from Japanese coastlines for antibacterial activity against Propionibacterium acnes, and found a novel antibacterial compound, which we named Sargafuran, from the MeOH extract of the marine brown alga, Sargassum macrocarpum. Sargafuran has low cytotoxicity, and the MIC against P. acnes was 15 microg ml(-1), showing a broad antibacterial activity against Gram-positive bacteria. A time-kill study showed that Sargafuran was bactericidal and completely killed P. acnes at 4 x MIC by lysing bacterial cells. These results suggest that Sargafuran might be useful as a lead compound to develop new types of anti-P. acnes substances and new skin care cosmetics to prevent or improve acne.

A chlorophyll c2 analogue from the marine brown alga Eisenia bicyclis inactivates the infectious hematopoietic necrosis virus, a fish rhabdovirus

We screened in vitro antiviral activity against a salmonid pathogenic virus, infectious hematopoietic necrosis virus (IHNV), from the extracts of a total of 342 species of marine algae collected from the Japanese coastline. The anti-IHNV activity was found primarily in MeOH extracts, and the extract from one marine brown alga in particular, Eisenia bicyclis, showed high anti-IHNV activity. The anti-IHNV compound was isolated and purified as MC15 from the E. bicyclis extract, and the chemical structure was determined by several spectrometric analyses. The antiviral compound was proved to be a chlorophyll c2 derivative lacking the metal ion Mg(2+). MC15 showed similar antiviral activity against other salmonid enveloped viruses such as Paralichthys olivaceus virus and Oncorhynchus masou virus, and stability against any pH and temperatures up to 100 degrees C. No cytotoxicity was observed at up to 5 microg/ml. The antiviral mechanism of MC15 appears to be direct inactivation of the viral particles. A time course study showed that the inactivation of IHNV was completed within 40 min when 200 PFU of IHNV was reacted with MC15 at 800 ng/ml.

Prevention of aflatoxin B1-initiated hepatotoxicity in rat by marine algae extracts

Chemoprevention by extracts of Laurencia obtusa (E1) and Caulerpa prolifera (E2) collected from the Egyptian coast of the Red Sea against aflatoxin B(1) (AFB(1))-initiated hepatotoxicity in female Sprague-Dawley rats has been studied. Animals were fed aflatoxin-contaminated diet (3 mg kg(-1) diet) for 6 days then treated orally with pure aflatoxin B(1) (AFB(1)) (200 microg kg(-1) b.w.) for 4 days either in combination with or before E1 or E2 administration (50 mg kg(-1) b.w.). AFB(1) resulted in a signicant increase in serum alpha fetoprotein, carcinoembryonic antigen, tumor necrosis factor alpha, nitric oxide, interleukin-1alpha, procollagen III and lipid peroxidation level in the liver. It caused a signicant decrease in food intake, body weight, serum leptin, the activities of glutathione peroxidase, superoxide dismutase and DNA and RNA concentrations in the liver. Cotreatment with AFB(1) and E1 or E2 resulted in an obvious improvement in all tested parameters. Noteworthy, E2 was more effective than E1 in the protection against AFB(1)-induced hepatotoxicity.

Inhibitory action of marine algae extracts on the Trypanosoma cruzi dihydroorotate dehydrogenase activity and on the protozoan growth in mammalian cells

Trypanosoma cruzi, the causative agent of Chagas' disease, replicates in mammalian cells and relies on the de novo pyrimidine biosynthetic pathway that supplies essential precursors for nucleic acid synthesis. The protozoan dihydroorotate dehydrogenase (DHOD), the fourth enzyme of the pathway catalyzing production of orotate from dihydroorotate, markedly differs from the human enzyme. This study was thus aimed to search for potent inhibitors against T. cruzi DHOD activity, and a number of methanol extracts prepared from green, brown, and red algae were assayed. The extracts from two brown algae, Fucus evanescens and Pelvetia babingtonii, yielded 59 and 58% decrease in the recombinant DHOD activity, respectively, at the concentration of 50 microg/ml. Inhibition by these extracts was noncompetitive with respect to dihydroorotate, with apparent Ki values of 35.3+/-5.9 and 10.3+/-4.4 microg/ml, respectively. Further, in an in vitro T. cruzi-HeLa cell infection system, ethanol-reconstituted F. evanescens and P. babingtonii extracts at the concentration of 1 microg/ml, respectively, decreased significantly the infection rate of host cells and the average parasite number per infected cell. These results imply that F. evanescens and P. babingtonii contain inhibitor(s) against the T. cruzi DHOD activity and against the protozoan infection and proliferation in mammalian cells. Identification of inhibitor(s) in these two brown algae and further screening of other marine algae may facilitate the discovery of new, anti-trypanosomal lead compounds.

Growth-inhibitory effects of the red alga Gelidium amansii on cultured cells

The objective of this study was to investigate the effects of Gelidium amansii, an edible red agar cultivated off the northeast coast of Taiwan, on the growth of two lines of cancer cells, murine hepatoma (Hepa-1) and human leukemia (HL-60) cells, as well as a normal cell line, murine embryo fibroblast cells (NIH-3T3). The potential role of G. amansii on the induction of apoptosis was also examined. The results indicated that all extracts from G. amansii, including phosphate-buffered saline (PBS) and methanol extracts from dried algae as well as the dimethyl sulfoxide (DMSO) extract from freeze-dried G. amansii agar, inhibited the growth of Hepa-1 and NIH-3T3 cells, but not the growth of HL-60 cells. Annexin V-positive cells were observed in methanol and DMSO extract-treated, but not PBS extract-treated Hepa-1 and NIH-3T3 cells, suggesting that the lipid-soluble extracts of G. amansii induced apoptosis. In summary, extracts of G. amansii from various preparations exhibited antiproliferative effects on Hepa-1 and NIH-3T3 cells, and apoptosis may play a role in the methanol and DMSO extract-induced inhibitory effects. However, the antiproliferative effects of PBS extracts was not through apoptosis. Moreover, the growth-inhibitory effects of G. amansii were not specific to cancer cells.