JOURNAL OF MEDICINAL FOOD J Med Food 13 (5) 2010, 1232–1239 # Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition DOI: 10.1089=jmf.2010.1124
The Antioxidant Properties of Ethanol Extracts and Their Solvent-Partitioned Fractions from Various Green Seaweeds MyoungLae Cho,1 Il-Jun Kang,2 Moo-Ho Won,3 Hyi-Seung Lee,4 and SangGuan You1 1
Department of Marine Food Science and Technology, Gangneung-Wonju National University, Gangneung, Gangwon; 2 Department of Food Science and Nutrition; 3Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chuncheon; and 4Marine Natural Products Laboratory, Korea Ocean Research and Development Institute, Ansan, Republic of Korea ABSTRACT The antioxidant activities of the ethanol (EtOH) extracts from the green seaweeds Enteromorpha compressa, Capsosiphon fulvescens, Chaetomorpha moniligera, and Ulva pertusa, as well as their solvent-partitioned fractions, were investigated, and their antioxidant activities were correlated with total phenolic and flavonoid contents. The EtOH extracts and their solvent-partitioned fractions showed 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH ) radical scavenging activities with strong reducing ability. The most effective antioxidant properties were observed from the EtOH extracts of E. compressa and C. fulvescens. Among the solvent-partitioned fractions obtained with n-hexane, chloroform (CF), and ethyl acetate, the CF fractions from E. compressa and C. fulvescens exhibited higher radical scavenging activities and stronger reducing ability than other fractions. The OH radical scavenging capacity and reducing power of these fractions were comparable to those of a positive control, a-tocopherol, at concentrations of 0.06–1.0 mg=mL. Total phenolic contents showed little correlation (r2 ¼ 0.22–0.42) with the antioxidant properties; however, significant correlation (r2 ¼ 0.73–0.96) was observed with flavonoid contents, implying that the flavonoid constituents contribute substantially to the antioxidant properties of the extracts. The overall results suggested that the green seaweeds (E. compressa and C. fulvescens), especially their CF fractions, could be good sources of natural antioxidants and of highly beneficial ingredients for healthcare products, such as nutraceuticals, supplements, and cosmeceuticals. KEY WORDS: antioxidant 2,2-diphenyl-1-picrylhydrazyl flavonoid content green seaweed hydroxyl radical reducing power
Marine resources have attracted attention in the search for bioactive compounds that may be used for new medicinal and functional food ingredients. Approximately 8,000 species of marine algae have been identified and grouped into different classes, including brown, red, and green seaweeds. Recently, brown and red seaweeds have been reported to be rich sources of antioxidants, such as phylopheophylin in Eisenia bicyclis, phlorotannins in Sargassum kjellamanianum, fucoxanthin in Hijikia fusiformis, and chlorophyll analogs in Porphyra yezoensi.9–12 It has also been suggested that the antioxidant activity of the extract from the brown seaweed Sargassum pallidum might be related with its phenolic substrates, phlorotannins.13 Ganesan et al.14 also reported a relationship between the antioxidant activity and total phenolic content of extracts from various red seaweeds. Conversely, in a study of extracts from the brown seaweed Sargassum siliquastrum the total phenolic content of the extracts was not correlated with antioxidant activity.15 These results imply that not only the total phenolic content, but also other constituents, might affect the antioxidant activity of extracts from marine algae. Yet, despite extensive research on the antioxidant potential of extracts from
INTRODUCTION
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eactive oxygen species (ROS), such as hydroxyl (OH ), superoxide, and peroxyl radicals, are generated in living organisms during metabolism.1,2 Excessive amounts of ROS may be a primary cause of biomolecular oxidation, which may contribute to various diseases, such as cancer, stroke, and diabetes, as well as the degenerative processes associated with aging.3–6 The negative effects of oxidative stress have been mitigated by some antioxidants, such as tert-butylated hydroxyanisole, tert-butylated hydroxytoluene, and propyl gallate; however, these synthetic antioxidants were found to be toxic and carcinogenic in animal models.7,8 Thus, safety concerns about synthetic antioxidants have led to an increasing interest in the development of safe and inexpensive supplements of natural origin. Manuscript received 30 March 2010. Revision accepted 17 June 2010. Address correspondence to: SangGuan You, Department of Marine Food Science and Technology, Gangneung-Wonju National University, Gangneung, Gangwon, 210-702, Republic of Korea, E-mail:
[email protected]
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ANTIOXIDANT ACTIVITIES OF GREEN SEAWEEDS
various types of algae, few studies have evaluated the antioxidant compounds in green seaweeds, which are ubiquitous, easily cultivated, and important natural resources.16 In addition, little information is available on the relationships between the active compounds and antioxidant activity of green seaweeds. The objective of this study, therefore, was to determine the antioxidant activity of the ethanol extracts and their various solvent-partitioned fractions from four different green seaweeds, including Enteromorpha compressa, Capsosiphon fulvescens, Chaetomorpha moniligera, and Ulva pertusa. The antioxidant activities of the extracts and solvent-partitioned fractions were correlated with the total phenolic and flavonoid contents. MATERIALS AND METHODS Materials Four green seaweeds (E. compressa, C. fulvescens, C. moniligera, and U. pertusa) were collected from the coast of Gangneung, Gangwon Province, Republic of Korea in March 2009. The seaweeds were washed with distilled water and air-dried at 608C. The dried seaweeds were milled with a blender, passed through a sieve (clearance,
