Antioxidant activity of Gracilaria edulis(Rhodophyseae) in Sri Lanka

Abstract

In recently marine seaweeds especially Gracilaria edulis are used to produce new drugs and healthy delicious low calorie foods such as jelly, jams, puddings, and soup which are known as primary source of secondary metabolite and to be used as natural antioxidants and antimicrobials. The purpose of this study was determined the antioxidant activity of G.edulis. Methanol extract of G.edulis were prepared in different concentrations such as 5, 10, 15, 20, 25 and 30 µg/ml. The antioxidant activity of G.edulis was determined by hydrogen peroxide scavenging assays in absorbance at 230 nm. In 30µg/ml methanol extract of G.edulis was shown the highest total antioxidant activity (p<0.05) while compared with other G.edulis sample concentration. Steady state antioxidant and free radical scavenging activities of methanol extract of G.edulis were exhibited at its 15ug/ml. In IBM SPSS package 2010, chi squared test and Paired T-Test were clearly illustrated the absorbance, inhibition or percentage scavenging of hydrogen peroxide depend on the concentration of the G.edulis methanol extract. These two statistical tests did tell about the difference between the concentration of the methanol extract of the G.edulis (p<0.05) and antioxidant activity. While methanol extract of G.edulis concentration increase, Hydrogen peroxide absorbance was decreased, the inhibition or percentage scavenging of hydrogen peroxide was increased and antioxidant activity was also increased. The antioxidant activity of G.edulis

methanol extract were determined and compared with other aromatic compounds such

were 2, 4 dinitro phenyl hydrazine and Aniline derivatives. H₂O₂ Scavenging activity assay was used to analyze the antioxidant activity to all investigated series concentration compounds. Aniline compounds were more active than other tested aromatic compounds. Antioxidant activity of these tested compounds depends on presence of active groups and its Position and number. OH and NH₂ was highly active their presence in ortho followed by para and meta. NH₂ electron donor substitution group transfer its electron to free radical source becoming itself a radical cation. Therefore it gives positive effect to H₂O₂ scavenging activity and antioxidant activity and had lower IP value. NO₂ groups are electron withdrawing group which groups were negative effects to H₂O₂ scavenging activity antioxidant activity. Absorbance were highly in 2, 4 dinitro aniline followed by 2, 4 dinitro phenyl hydrazine, aniline and G.edulis due to the H₂O₂ scavenging activity. Hence antioxidant activity or H₂O₂ scavenging activity was highly in G.edulis, followed by aniline, 2,4 dinitro phenyl hydrazine and 2,4 dinitro aniline. Finally G.edulis sample was recorded prominent antioxidant activity. This study is used in future for product development incorporation of dried seaweed G. edulis into bakery Products.