In vitro antioxidant activity, phenolic content and profile of Cystoseira barbata from Romanian Black Sea

The Romanian Black Sea has abundant seaweed resources, but little effort has been done to screen their biological potential. The aim of the present study was to assess the in vitro antioxidant activity, phenolic content and profile of Cystoseira barbata (Stackhouse) C. Agardh, Cystoseiraceae, a brown alga inhabiting the costal line of Romanian Black Sea. The 70% acetone extract from C. barbata was investigated by HPLC-DAD-ESI-MSⁿ. Total phenolic content was determined by Folin-Ciocalteu method. The antioxidant activity was assessed using four methods (2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical cation scavenging assay, reducing power and 15-lipoxygenase inhibition assay); gallic acid and caffeic acid were used as positive controls. Several phlorotannins (fucodiphloroethol, fucophloroethols with six, seven and eight phloroglucinol units with [M+H]⁺ at m/z 499, 747, 871 and 995, respectively) were tentatively identified on the basis of their characteristic MS fragmentation pattern. A total phenolic content of 236.03 ± 1.20 mg gallic acid equivalents/g extract was determined. In all antioxidant assays, the activity of the extract increased significantly in a concentration dependent manner. The EC₅₀ values in the DPPH, ABTS and reducing power assays were 88.5 ± 0.3, 13.9 ± 0.2 and 17.6 ± 0.0 µg/mL, respectively. The extract showed high 15-lipoxygenase inhibition capacity (EC₅₀= 47.3 ± 1.5 µg/mL), when compared with positive controls (EC₅₀= 39.0 ± 0.7 µg/mL for gallic acid and 25.5 µg/mL for caffeic acid). The remarkable antioxidant activity of C. barbata suggests its potential use in the food and pharmaceutical industries.

Acknowledgments: This paper was published under the frame of European Social Found, Human Resources Development Operational Programme 2007 – 2013, project no. POSDRU/159/1.5/136893.