Antioxidant properties of a new antioxidative peptide from algae protein waste hydrolysate in different oxidation systems
Introduction
In the normal cells, free radicals and reactive oxygen species (ROS) can be effectively eliminated by an enzyme-mediated system such as superoxide dismutase, peroxidase, glutathione peroxidase and non-enzymatic factors such as ascorbic acid, protein. When the homeostasis between the prooxidant formation and antioxidant capacity is disrupted, whereby prooxidant formation exceeds antioxidant capacity, oxidative damage will accumulate and result in patho-physiological events. Accumulating evidence indicates that active oxygen and free radicals would attack key biological molecules such as DNA, protein, and lipid that leading to many degenerative disease conditions (Suja et al., 2004), such as cancer (Leanderson et al., 1997), gastric ulcers (Debashis et al., 1997), Alzheimer’s, arthritis and ischemic reperfusion (Vajragupta et al., 2000). To maintain the prooxidant–antioxidant balance, the removal of free radicals and ROS is probably one of the most effective defenses of a living body against various diseases (Yang et al., 2001, Butterfield et al., 2002, Fazlul and Li, 2002).
Many synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG) have been used to retard the oxidation process; however, the use of synthetic antioxidants must be under strict regulation due to potential health hazards (Park et al., 2001). The search for natural antioxidants as alternatives is therefore of great interest among researchers.
Recently, bioactive peptides from enzymatic hydrolysis of various food proteins such as soy protein, casein, whey protein, gelatin and wheat gluten have been shown to possess antioxidative activity (Elias et al., 2008). However, antioxidative peptides from marine food sources are gaining attention as new antioxidative alternatives in the last few years (Je et al., 2005, Mendis et al., 2005, Rajapakse et al., 2005, Qian et al., 2008a, Qian et al., 2008b). Chlorella vulgaris is a popular edible microalgae in Japan, so its safety is well established (Suetsuna and Chen, 2001). Presently, the commercial applications of microalgae are as nutritional supplements, natural dyes and skin care products (Spolaore et al., 2006), but there are no studies reporting the antioxidative activity of microalgae protein-derived peptides. Algae protein waste is a by-product derived from water-extraction process of microalgae, C. vulgaris during algae essence manufacturing. The underutilized algae wastes, containing above 50% protein, have low economical value to be used as animal feed. The pepsin hydrolysate from algae protein waste exhibited antioxidative activity in preliminary experiments, indicating that algae waste might become a new protein source for selection of novel antioxidative peptides. In this study, we used pepsin protease to produce biologically active hydrolysate from algae protein waste, and purified a bioactive peptide with free radical scavenging activity. We further investigated its antioxidative activity in different oxidation systems in comparison with those of synthetic antioxidant BHT and natural antioxidants Trolox, and ascorbic acid. In addition, the protective effect of the purified peptide against oxidation-induced DNA and cellular damage also was determined.
Section snippets
Materials
Algae waste, the by-product in algae essence manufacturing of Taiwan, was dried and kept at 4 °C prior to use. ABTS (2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, indoxyl-β-d-glucuronide (IBG), FeSO4 · 7H2O, lucigenin, arginine, methylglyoxal, (3-(4,5-dimethyl-2-yl)-2,5-diphenyltetrazolium bromide, fetal bovine serum (FBS) and MTT (1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan) were from Sigma Chemical Co. (St. Louis, MO, USA).
Preparation of algae protein-derived bioactive peptides
The algae protein waste hydrolysate was prepared by pepsin hydrolysis at a temperature of 50 °C for 15 h and the product yield was 48.3%. As depicted in Fig. 1, the pepsin released a mixture of extremely small peptides with high antioxidative activity against ABTS radicals (IC50 93.4 μg/ml) from algae protein, compared to no observable antioxidative effect in intact algae proteins (data not shown). The hydrolysis was necessary in order to release antioxidative peptides from an inactive, intact
Conclusion
There are numerous reports on bioactive compounds in microalgae. There are no reports to date regarding the antioxidative effect of peptides from algae protein waste. We investigated the antioxidative potency of the peptide from algae in different mechanisms of oxidation in vitro. In addition, the protective abilities of the purified peptide in oxidation-induced cell death and DNA damage were also tested. We have shown that the peptide from algae protein has a greater efficiency in scavenging
Acknowledgements
We thank National Chiao Tung University, MOE ATU Program and National Science Council, ROC, Project No. NSC-96-2313-B-005--008-MY3 for financially supporting this research.
References (35)
- et al.
Perhydroxyl radical (HOO) initiated lipid peroxidation. The role of fatty acid hydroperoxides
J. Biol. Chem.
(1991) - et al.
A new approach to assess the total antioxidant capacity using the TEAC assay
Food Chem.
(2004) - et al.
Nutritional approaches to combat oxidative stress in Alzheimer’s disease
J. Nutr. Biochem.
(2002) - et al.
Hyperoxia induces DNA damage in mammalian cells
Free Radic. Biol. Med.
(1993) - et al.
Inducible nuclear factor-κB activation contributes to chemotherapy resistance in gastric cancer
J. Am. Coll. Surg.
(2004) - et al.
Angiotensin I-converting enzyme inhibitor derived from soy protein hydrolysate and produced by using membrane reactor
Food Chem.
(2006) - et al.
Antioxidant properties of methanolic extracts from Agaricus blazei with various doses of γ-irradiation
Food Sci. Technol.
(2006) - et al.
Antioxidant activity of a peptide isolated from Alaska Pollack (Theragra chalcogramma) frame protein hydrolysate
Food Res. Int.
(2005) - et al.
Green tea polyphenols inhibits oxidant-induced DNA strand breakage in cultured lung cells
Free Radic. Biol. Med.
(1997) - et al.
Investigation of jumbo squid (Dosidicus gigas) skin gelatin peptides for their in vitro antioxidant effects
Life Sci.
(2005)