Chlorella ethanol extract induced phase II enzyme through NFE2L2 (nuclear factor [erythroid-derived] 2-like 2, NRF2) activation and protected ethanol-induced hepatoxicity.

In this study, we investigated the hepatoprotective effects of ethanol extracts from Chlorella vulgaris (CH) on animals. We measured its effect on the quinone reductase (QR) activity in Hepa1c1c7 cells, finding that CH induced a significantly higher QR activity in these cells. We isolated the active fraction (CH F4-2) from CH using chromatography methods. CH F4-2 may activate cellular antioxidant enzymes through upregulation of the Nrf2 pathway in hepatocarcinoma cells with CH F4-2 (25.0-200 µg/mL) for 48 h. Furthermore, CH F4-2 increased the expression of NQO1 [ NAD(P)H: quinone oxidoreductase, also known as QR], heme oxygenase-1, and glutathione-S-transferase P. Moreover, we found that ethanol-induced hepatic pathological changes-elevations in glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, γ-glutamyltransferase, and lactate dehydrogenase-were significantly decreased. The inhibitory effect of CH on alcohol-induced liver injury was associated with the suppression of alcohol-induced increases in intestinal permeability. The ethanol extract from CH was found to induce QR activation, making it a potentially good candidate for a hepatoprotection agent.

Characterization of bioactive peptides obtained from marine invertebrates.

Bioactive peptides as products of hydrolysis of diverse marine invertebrate (shellfish, crustacean, rotifer, etc.) proteins are the focus of current research. After much research on these muscles and by-products, some biologically active peptides were identified and applied to useful compounds for human utilization. This chapter reviews bioactive peptides from marine invertebrates in regarding to their bioactivities. Additionally, specific characteristics of antihypertensive, anti-Alzheimer, antioxidant, antimicrobial peptide enzymatic production, methods to evaluate bioactivity capacity, bioavailability, and safety concerns of peptides are reviewed.

Angiotensin I converting enzyme inhibitory peptide extracted from freshwater zooplankton.

In this study, hydrolysates obtained from the freshwater rotifer Brachionus calyciflonus were investigated for angiotensin I converting enzyme (ACE) inhibitory peptides. Freshwater rotifer protein was hydrolyzed using six separate enzymes in a batch reactor. The peptic hydrolysate had the highest ACE inhibitory activity compared to the other hydrolysates. The highest ACE inhibitory peptide was separated using Sephadex G-25 column chromatography and high-performance liquid chromatography on a C18 column. The 50% inhibitory concentration (IC(50)) value of purified ACE inhibitory peptide was 40.01 microg/mL. ACE inhibitory peptide was identified as being seven amino acid residues of Ala-Gln-Gly-Glu-Arg-His-Arg by N-terminal amino acid sequence analysis. The IC(50) value of purified ACE inhibitory peptide was 47.1 microM, and Lineweaver-Burk plots suggested that the peptide purified from rotifer protein acts as a competitive inhibitor against ACE. The results of this study suggest that peptides derived from freshwater rotifers may be beneficial as antihypertension compounds in functional foods or as pharmaceuticals.

Purification and antioxidant properties of bigeye tuna (Thunnus obesus) dark muscle peptide on free radical-mediated oxidative systems.

To produce bioactive peptides from by-products of fish processing, bigeye tuna dark muscle was hydrolyzed using various enzymes (alcalase, alpha-chymotrypsin, neutrase, papain, pepsin, and trypsin), and the hydrolysates were evaluated for antioxidant activity. Considering the results of degree of hydrolysis and antioxidant activities, peptic hydrolysate was used for further studies to identify a potent antioxidant peptide. Antioxidant peptide was purified using consecutive chromatographic methods and was identified as being H-Leu-Asn-Leu-Pro-Thr-Ala-Val-Tyr-Met-Val-Thr-OH (MW 1,222 Da) by quantitative time-of-flight electrospray ionization mass spectrometry. Purified antioxidant peptide from bigeye tuna dark muscle (APTDM) was investigated for its antioxidant activities using both free radical scavenging effects and polyunsaturated fatty acid (PUFA) peroxidation inhibitory activity. The results showed that APTDM effectively quenched with low 50% inhibitory concentration values compared to vitamin C as a positive control against four different free radicals: 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, superoxide, and alkyl radical. APTDM also inhibited PUFA peroxidation in a linoleic acid emulsion system, and the activity was similar to that of alpha-tocopherol. We further investigated its antioxidant activities on cellular systems, and the results showed that APTDM significantly scavenged cellular radicals and enhanced the viability of tert-butyl hydroperoxide-induced cytotoxicity. These results indicate that APTDM or a peptide fraction containing APTDM would be a beneficial ingredient for functional food and/or pharmaceuticals.

Free radical scavenging activity of a novel antioxidative peptide isolated from in vitro gastrointestinal digests of Mytilus coruscus.

A low-molecular-weight peptide with potent antioxidative activity was obtained from Mytilus coruscus muscle protein using an in vitro gastrointestinal digestion system. The potent antioxidant peptide, which was identified as Leu-Val-Gly-Asp-Glu-Gln-Ala-Val-Pro-Ala-Val-Cys-Val-Pro (1.59 kDa), exhibited higher protective activity against polyunsaturated fatty acid (PUFA) peroxidation than the native antioxidants, ascorbic acid and alpha-tocopherol. In a free radical scavenging assay using electron spin resonance spectroscopy, hydroxyl radical formation was quenched by 75.04% in the presence of M. coruscus peptide (50 microg/mL), which was similar to ascorbic acid. In addition, the purified peptide could also quench super-oxide and carbon-centered radicals, but those activities were weaker than for ascorbic acid. This study showed that the low-molecular-weight peptide released from in vitro gastrointestinal digestion of mussel exhibited potent antioxidant potential by inhibiting the formation of reactive oxygen species formed by the peroxidation of PUFAs.

Phlorotannins in Ecklonia cava extract inhibit matrix metalloproteinase activity.

Matrix metalloproteinase (MMP) inhibitors have been identified as potential therapeutic candidates for metastasis, arthritis, chronic inflammation and wrinkle formation. For the first time here we report a detailed study on the inhibitory effects of phlorotannins in brown algae, Ecklonia cava (EC) on MMP activities in cultured human cell lines. A novel gelatin digestion assay could visualize complete inhibition of bacterial collagenase-1 activity at 20 microg/ml of EC extract during preliminary screening studies. Sensitive fluorometric assay revealed that EC extract can specifically inhibit both MMP-2 and MMP-9 activities significantly (P < 0.001) at 10 microg/ml. In addition, artificially induced activities of MMP-2 and MMP-9 in human dermal fibroblasts and HT1080 cells were inhibited by EC extract in a more or less similar manner to the positive control doxycycline. Even though the expression levels of MMPs differ from one cell type to the other, gelatin zymography clearly revealed that both MMP expression and activity in cells can be inhibited by EC extract. More interestingly, EC extract did not exert any cytotoxic effect even at 100 microg/ml anticipating its potential use as a safe MMP inhibitor.

Purification and in vitro antioxidative effects of giant squid muscle peptides on free radical-mediated oxidative systems.

Low molecular weight peptides obtained from ultrafiltration (UF) of giant squid (Dosidicus gigas) muscle protein were studied for their antioxidative effects in different in vitro oxidative systems. The most potent two peptides, Asn-Ala-Asp-Phe-Gly-Leu-Asn-Gly-Leu-Glu-Gly-Leu-Ala (1307 Da) and Asn-Gly-Leu-Glu-Gly-Leu-Lys (747 Da), exhibited their antioxidant potential to act as chain-breaking antioxidants by inhibiting radical-mediated peroxidation of linoleic acid, and their activities were closer to highly active synthetic antioxidant, butylated hydroxytoluene. Addition of these peptides could enhance the viability of cytotoxic embryonic lung fibroblasts significantly (P<.05) at a low concentration of 50 microg/ml, and it was presumed due to the suppression of radical-induced oxidation of membrane lipids. Electron spin trapping studies revealed that the peptides were potent scavengers of free radicals in the order of carbon-centered (IC(50) 396.04 and 304.67 microM), hydroxyl (IC(50) 497.32 and 428.54 microM) and superoxide radicals (IC(50) 669.34 and 573.83 microM). Even though the exact molecular mechanism for scavenging of free radicals was unclear, unusually high hydrophobic amino acid composition (more than 75%) of giant squid muscle peptides was presumed to be involved in the observed activities.