Assessment of antioxidant activity of extracts from marine algae from the Sea of Japan in vitro and in vivo

Abstract

Marine algae are a source of important biologically active substances: lipids, amino acids, phenolic compounds, polycarbohydrates, etc. Polyphenolic substances are one of the important group of constituents of marine origin with high antioxidant activity, which play an important role in the life of marine macrophytes, allowing them quickly respond to external stress by performing protective functions. At the same time, the multicomponent composition of the phenolic constituent of the extract from marine algae provides a wide spectrum of its pharmacological activity, including a regulatory effect on numerous homeostasis disorders at pathological processes in the body of humans and animals. Wherein, the available opportunities for the practical use of extracts from marine algae have not yet been depleted, and its study is a topical issue of modern science. The purpose of this study was a comparative estimation of the antioxidant activity of water alcohol extracts from thalli of brown alga - Sargassum pallidum (Turner) C. Agardh, green alga - Ulva lactuca Linnaeus, 1753, red alga - Ahnfeltia tobuchiensis (Kanno et Matsubara) on Makienko, and their impact on the indices of the endogenous antioxidant system of liver and blood in mice under experimental stress. Algae were collected in the summer time in the coastal waters of the Peter the Great Bay of the Sea of Japan. Collected algae were dried at t <50⁰С, grounded in a laboratory mill to a particle size of 0.5 - 1 mm and extracted with 70% ethanol by the repercolation method. The evaluation of the quantitative content of polyphenols in the extracts of the studied marine algae showed that most of them were found in the extract of brown alga S. pallidum (218.2 ± 20.3 mg-Eq GA/g dry extract). In the extract of the green alga U. lactuca, this characteristic was 16.2 ± 1.8 mg-Eq GA/g dry extract, and in the red alga A. tobuchiensis - 9.1 ± 1.6 mg-Eq GA/g dry extract. Wherein, the antiradical activity of the extract from the brown algae S. pallidum towards to cation radical ABTS⁺ and the alkyl peroxyl radical was significantly higher than the one of the extracts from U. lactuca and A. tobuchiensis. The experiment was carried out on white outbred male mice weighing 20-30 g, kept in standard vivarium conditions. Acute stress was modeled by vertical fixation of animals for the dorsal neck fold for 24 hours. Alcohol-free algae extracts were administered to mice as an aqueous suspension at a dose of 100 mg of total polyphenols per kg of body weight into the stomach through a tube twice: immediately before vertical fixation and 6 hours after the first introduction. Distilled water was administered to animals of the control group and the "stress" group in a volume equal to one of the administered preparations. All the attributes of stress were manifested in this model: adrenal hypertrophy, involution of the thymus and spleen, ulceration of the gastric and intestinal mucosa. Also were noted disturbances of the antioxidant defense system, which manifested in a decrease of antioxidant enzymes activity in the blood plasma, the content of reduced glutathione in liver, as well as in an increase of the malondialdehyde level in blood plasma. Under the action of the extracts in all groups of animals with stress it was observed a tendency to stabilization of the studied parameters of antioxidant protection. Wherein, these indices in mice receiving extracts from U. lactuca and A. tobuchiensis were inferior to those in the group of animals receiving S. pallidum extract. In the group of animals treated with S. pallidum extract, there were no significant differences from the control values in terms of antioxidant protection parameters. This is because the main components of the polyphenolic fractions of green and red algae are represented by monomeric flavonoids. While the brown algae contain high molecular weight phlorotannins, which exhibit higher antioxidant activity in contrast to low molecular weight polyphenolic fractions of green and red algae.

Keywords: seaweed, polyphenols, antioxidant activity, stress, mice