Analysis of Phytochemical Content and Bioactive Properties of Kappaphycus alvarezii Methanolic Extract

Abstract

Seaweeds are one of the important living resources of the marine environment. Kappaphycus alvarezii, a marine red seaweed, is primarily grown in Sri Lanka and has been reported to contain valuable bioactive compounds; however, its importance remains unknown. The bioactive properties, including antioxidant, antidiabetic, antiinflammatory, and antibacterial activities of 70% methanolic extract of K. alvarezii were investigated using an in vitro method. K. alvarezii powder was extracted using 70% methanol (1:10) and freeze-dried. The yield of the methanolic extract was 22.16 ± 0.49%. Total phenolic and flavonoid contents were 0.99 ± 0.03 mg gallic acid equivalents/g of extract and 0.40 ± 0.06 mg rutin equivalents/g of extract, respectively. The crude extract showed antioxidant activities, including 2,2-diphenyl-1- picrylhydrazyl (DPPH) scavenging activity (IC50: 10.48 ± 0.22 mg/mL), total antioxidant (3.16 ± 0.06 mg ascorbic acid equivalents/g extract), reducing ability (1.67 ± 0.02 mg ascorbic acid equivalents/g extract), and H2O2 scavenging activity (IC50:2.06 ± 0.07 mg/mL). The antidiabetic potential was assessed by inhibiting alpha-amylase activity, with an IC50 value of 16.40 ± 0.72 mg/mL. Antioxidant and antidiabetic activities increased significantly with increasing concentration, indicating a dosedependent response. It showed anti-inflammatory activities, including inhibition of bovine serum albumin denaturation (50.00 ± 3.72%), trypsin inhibition (24.33 ± 0.84%), and heat-induced haemolysis (22.62 ± 1.09%) at 1 mg/mL and antimicrobial potential with inhibition zones at 250 mg/mL and 500 mg/mL concentration against Staphylococcus aureus (8.50 ± 0.71 mm and 10.50 ± 0.71 mm), Bacillus subtilis (10.50 ± 0.71 mm and 13.50 ± 0.71 mm), and Escherichia coli (8.50 ± 0.35 mm and 11.25 ± 0.35 mm), respectively. However, no activity against Salmonella enterica. Results demonstrated that methanolic K. alvarezii extract could be used as a potential source of bioactivity and may have great importance as a therapeutic agent in the food and pharmaceutical industries.