Bio-Evaluation of Two Red Seaweeds for Their Cytotoxic and Antioxidant Activities In Vitro

Abstract

This article evaluates the cytotoxic and antioxidant activities of the seaweeds Amphiroa fragilissima and Asparigopsis taxiformis methanolic extracts in-vitro. The aim of this study was to test the selected red seaweed extracts for their cytotoxic activity by Brine shrimp lethality assay and antioxidant properties by in-vitro free radical scavenging assays such as, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, reducing power assay, and metal ion chelating assay. Also, the total phenolic content (TPC) of the seaweed extracts was also determined. In the brine shrimp lethality test, A. fragilissima and A. taxiformis demonstrated mild cytotoxic activity of 53.33 ± 2.58 and 58.33 ± 2.58 % at the highest concentration of 0.5mg/ml and 24 h incubation time. The total phenolic content of both the seaweed extracts were expressed as mg gallic acid equivalent (GAE)/ gram dry seaweed extract and consecutively decreased as follows: A. taxiformis (8.521 ± 0.284) > A. fragilissima (8.220 ± 0.214). Percent DPPH radical scavenging activities of the two studied red seaweed extracts were dose dependant and was highest in the extract of A. fragilissima (IC50 2.89 ± 0.061 mg/ml) when compared to A. taxiformis (IC50 3.38 ± 0.042 mg/ml), although none showed comparable activity to the standard ascorbic acid (ICM50 0.07 ± 0.002 mg/ml). Reducing power in seaweed methanolic extracts at all concentrations of 0.1, 0.5 and 1.0 and 2.0 mg/ml decreased in the order of BHT > A. fragilissima > A. taxiformis. The metal ion chelating efficacy was the highest in A. fragilissima (IC501.27 ± 0.018 mg/ml) followed by A. taxiformis (IC50 2.37 ± 0.172 mg/ml), respectively. The present study exemplifies that the methanolic extracts of Amphiroa fragilissima and Asparigopsis taxiformis have notable cytotoxic and antioxidant activities in in-vitro assay systems.