Screening of in Vitro Antioxidant Activity of Seaweed, Hypnea musciformis
Seaweeds are considered as a rich source of bioactive compounds as they are able to produce a great variety of secondary metabolites characterised by a broad spectrum of biological activities including antioxidant property. However, in contrast to terrestrial plants, only a few studies have reported the antioxidant activity of seaweeds. In the present study antioxidant activities of three different solvent extracts (hexane, methanol and aqueous) of Hypnea musciformis were evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay and phosphor molybdenum reduction assay. Total Phenolic Content (TPC) was evaluated using Folin-Ciocalteu method and the total flavonoid content was determined by the aluminium chloride (AlCl3) colourimetric method. Characterisation of the crude extracts were carried out using FT-IR analysis. The highest total antioxidant activity was recorded in methanol extract (14.50±0.58 AAE/g) whereas the lowest antioxidant activity was recorded in aqueous extract (0.75±0.29). The total antioxidant activity of hexane extract was recorded as 3.20±0.231 AAE/g. Butylated hydroxytoluene (BHT) was used as positive control and total antioxidant activity was recorded as 19.50±0.58 AAE/g. The highest DPPH antioxidant activity was obtained for methanol extract (IC50=28.00±2.31 mg/L) while the lowest activity was obtained for the aqueous extract (IC50=6006.00±6.93 mg/L). Gallic acid was used as the standard and BHT was used as the positive control and IC50 values were recorded as 3.50±0.38 mg/L and 24.00±1.15 mg/L respectively. The highest TPC was exhibited in methanol extract (14.02±0.03 GAE/g) whereas the lowest was recorded in aqueous extract 0.89±0.07 GAE/g. TPC of BHT was recorded as 254.93±4.43 GAE/g. The highest TFC was recorded in methanol extract (0.0170±0.04 QE/g) and the lowest TFC was recorded in aqueous extract (0.0098±0.14 QE/g). The TFC content of the hexane extract was 0.0102±0.13 QE/g. FT-IR analysis revealed the presence of alcohols/phenols, alkanes, carboxylic acids, alkenes, aromatics and aromatic amines, aliphatic amines in methanol crude extract. The study emphasises the importance of isolating and examining individual bioactive compounds present in H. musciformis for future research as it has revealed the antioxidant activities.
Keywords: Hypnea musciformis, Antioxidant activity, DPPH