Vimala Balasubramaniam¹*, Mohd Fairunizal Mohd Noh¹, Amin Ismail²
1. Nutrition, Metabolism & Cardiovascular Research Centre, Institute for Medical Research (IMR), National Institutes of Health (NIH), Ministry of Health Malaysia, Level 3, Block C7, No.1 Jalan Setia Murni U13, Setia Alam, 40170 Shah Alam, Selangor, Malaysia
2. Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
*Corresponding author: Vimala Balasubramaniam.
CITATION: Balasubramaniam, V., Mohd Noh, M. F., & Ismail, A. (2025). In vitro inhibition of carbohydrate-hydrolysing enzymes by Malaysian seaweed extracts: role of extraction solvent and active fractions. International Medical Research Journal, 11(2). https://doi.org/https://doi.org/10.63719/imrj.2025.11.02.001
ABSTRACT
Marine macroalgae or seaweeds, traditionally consumed in coastal regions, are rich in bioactive compounds with potential therapeutic benefits. This study investigated the inhibitory effects of ethanolic and methanolic extracts from three locally available edible seaweeds, namely Eucheuma denticulatum, Sargassum polycystum, and Caulerpa lentillifera, against α-amylase and α-glucosidase, key enzymes involved in postprandial glucose regulation in type 2 diabetes mellitus. Crude extracts were prepared using ethanol or methanol (1:20 w/v, 24 h maceration with stirring at room temperature), followed by in vitro enzyme assays using porcine pancreatic α-amylase and yeast α-glucosidase. Among the methanolic extracts, E. denticulatum exhibited the highest α-amylase inhibition (50% at 10 mg/mL), while the ethanolic extract inhibited 67%. S. polycystum and C. lentillifera showed moderate to low inhibition across both solvent extractions. The half maximal inhibitory concentration (IC₅₀) of ethanolic E. denticulatum extract was 1.99 mg/mL, indicating a potent inhibitory effect. Further fractionation of the ethanolic extract revealed that the ethyl acetate fraction had the strongest α-amylase inhibitory activity (49%), followed by acetone (42%) and hexane (36%), though all were lower than the crude extracts, suggesting possible synergistic interactions among the bioactive constituents. In contrast, none of the seaweed extracts exhibited notable α-glucosidase inhibition. These findings highlight the importance of solvent selection in extracting bioactive compounds and support the potential application of E. denticulatum, particularly its semi-polar constituents, as a promising candidate for functional food or nutraceutical applications that help regulate carbohydrate metabolism.
KEYWORDS: Malaysian seaweed, α-amylase inhibition, α-glucosidase inhibition, Eucheuma denticulatum, diabetes management
