Evaluation of Proximate Composition, Antioxidant Properties, and Phylogenetic Analysis of Two Edible Seaweeds
Rathinam Raja, Shanmugam Hemaiswarya, S. Sridhar, A. Arun, Venkatesan Ganesan, Elumalai Sanniyasi, Isabel S. Carvalho
Abstract
The present study was evaluated for the proximate composition (moisture, carbohydrate, protein, and lipid contents) of two seaweeds Gracilaria corticata (Rhodophyceaen) and Halimeda opuntia (Chlorophycean). Phylogenetic analysis based on the SSU (small subunit) rRNA ascertained their molecular identification. The results showed that the carbohydrate (5.72 ± 0.05 g/100 g), protein (42.38 ± 0.08 g/100 g), and total lipids (10.09 ± 0.06 g/100 g) are elevated in G. corticata when compared to H. opuntia. H. opuntia had a protein content of 3.51 ± 0.072 g/100 g and higher moisture content (95 ± 0.45 g/100 g). The methanolic extracts of G. corticata and H. opuntia were used to examine the antioxidants (viz. TPC, TFC, DPPH, and FRAP) and antidiabetic (α-glucosidase) properties. The antioxidant results of the methanolic extract of G.corticata exhibited a higher amount of phenolic compounds (13.37 ± 0.01 mg GAE/g dry wt.) compared to H. opuntia. But in the case of flavonoids, H.opuntia contained a slightly higher amount of quercetin equivalent 9.56 ± 0.26 mg/g dry wt. In FRAP, H.opuntia showed an elevated level (62.02 mg TE/g dry wt). DPPH scavenging activity in the seaweed extracts were recorded in the following order: H.opuntia and G.corticata. The amino acid content of H.opuntia was 0.097 ± 0.56 (mg/g) and 0.086 ± 0.42 (mg/g) was recorded in G.corticata.