Antioxidant, anti-inflammatory, and antibacterial activities of a 70% ethanol-Symphyocladia linearis extract

Abstract

Research on the potential biological activity of red alga Symphyocladia spp. has been limited to Symphyocladia latiuscula, which is widely used as a food ingredient in Korea. Here, we examined the biological activity of another species, Symphyocladia linearis, which is found in Korea and was reported as a new species in 2013. The aim of this study was to evaluate the antioxidant, anti-inflammatory, and antibacterial properties of a 70% ethanol extract of S. linearis. Antioxidant activity, which was evaluated using radical scavenging assays, revealed half maximal inhibitory concentration values for 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) of 34.57 and 11.70 μg/mL algal extract, respectively. Anti-inflammatory activity of the S. linearis ethanolic extract was evaluated using RAW 264.7 cells by measuring the inhibition of lipopolysaccharide-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production. The potential cytotoxicity of NO and PGE2 was first examined, confirming no toxicity at concentrations ranging from 10-100 μg/mL. NO production was inhibited 61.1% and 78.0% at 50 and 100 μg/mL S. linearis extract, respectively; and PGE2 production was inhibited 69.1%, 83.2%, and 94.8% at 25, 50, and 100 μg/mL S. linearis extract, respectively. Thus, the S. linearis extract showed very strong efficacy against PGE2 production. The cellular production of reactive oxygen species, measured using 2′,7′-dichlorofluorescin diacetate fluorescence, was inhibited 48.8% by the addition of 100 μg/mL S. linearis extract. Antibacterial activity was evaluated using the disc diffusion method and minimum inhibitory concentration (MIC). S. linearis was effective only against gram-positive bacteria, exhibiting antibacterial activity against Staphylococcus aureus with a MIC of 256 μg/mL extract and against Bacillus cereus with a MIC of 1,024 μg/mL extract. Based on these results, we infer that a 70% ethanolic extract of S. linearis possesses strong anti-inflammatory properties, and therefore has the potential to be used in the prevention and treatment of inflammatory and immune diseases.