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.
