1 Introduction
Overweight and obesity have become global health issues and are strongly associated with coronary heart disease, hypertension, and metabolic disorders. Existing pharmaceutical hypolipidemic and hypoglycemic agents often exhibit side effects, which drives interest in safe, natural alternatives for regulating blood glucose and lipids.
Seaweeds, fruits, and vegetables are rich in active compounds with anti-inflammatory, lipid-lowering, and hypoglycemic properties. Sargassum fusiforme shows antioxidant and weight-management activity; curcumin can modulate lipid metabolism; punicalagin exhibits anti-inflammatory and lipid-lowering effects. Screening for α-glucosidase and pancreatic lipase inhibitors among these natural actives provides a foundation for developing natural auxiliary hypoglycemic and hypolipidemic formulations.
2 Materials and Methods
2.1 Materials and Reagents
Sargassum fusiforme, curcumin, punicalagin, α-glucosidase, porcine pancreatic lipase, PNPG, 4-MUO, and standard inhibitors (acarbose and orlistat) were used in this study.
2.2 Instruments
A freeze dryer, rotary evaporator, refrigerated centrifuge, constant-temperature incubator, microplate reader, and ultrapure water system were employed.
2.3 Experimental Methods
2.3.1 Preparation of Sargassum fusiforme Aqueous Extract
Hydrated seaweed was extracted at a solid–liquid ratio of 1:50, heated at 85°C for 6 h, centrifuged, and freeze-dried to obtain the aqueous extract.
2.3.2 α-Glucosidase Inhibition Assay
The PNPG colorimetric method was used to determine inhibitory activity.
2.3.3 Pancreatic Lipase Inhibition Assay
4-MUO served as the substrate, and fluorescence intensity was measured to calculate inhibition levels.
2.3.4 Single-Factor Experiments
Based on IC₅₀ ratios of the three actives (150:6:2), a range of mass ratios was selected. At 0.5 mg/mL total concentration, inhibition rates against both enzymes were determined for each ratio.
2.3.5 Response Surface Design
A three-factor, three-level RSM design evaluated the effects of the three ingredient ratios on enzyme inhibition to determine the optimal composite formula.
3 Results and Analysis
3.1 Comparison of IC₅₀ Values
Punicalagin showed the strongest inhibitory activity:
α-glucosidase: IC₅₀ = 0.420 mg/mL
Pancreatic lipase: IC₅₀ = 0.090 mg/mL
Curcumin exhibited moderate activity, whereas Sargassum fusiforme extract showed weaker inhibition (IC₅₀ = 38.22 mg/mL and 1.02 mg/mL).
The average IC₅₀ ratio was approximately 150:6:2.
3.2 Single-Factor Experiments
3.2.1 Ratio of Sargassum fusiforme Extract
Inhibition of α-glucosidase decreased with higher proportions, while pancreatic lipase inhibition peaked at a ratio of 450. The optimal ratio selected was 450.
3.2.2 Ratio of Curcumin
Inhibition of α-glucosidase was highest at a ratio of 4, and pancreatic lipase inhibition peaked at 6. The optimal curcumin ratio determined was 4.
3.2.3 Ratio of Punicalagin
Under fixed conditions (450 Sargassum: 4 curcumin), gradual increases in punicalagin allowed identification of an optimal ratio around 2, forming the basis for RSM analysis.
3.3 Response Surface Analysis and Optimization
RSM showed the influence of the three ingredients on enzyme inhibition ranked as follows:
For α-glucosidase:
curcumin > punicalagin > Sargassum extract
For pancreatic lipase:
curcumin > Sargassum extract > punicalagin
Model optimization yielded an ideal mass ratio of:
150:6:3 (Sargassum extract : curcumin : punicalagin)
Measured inhibition results were:
α-glucosidase: 47.77%
Pancreatic lipase: 74.18%
Values closely matched model predictions, confirming model reliability.
3.4 Enzyme Inhibition of the Optimized Formula
The optimized composite formula exhibited IC₅₀ values of:
0.56 mg/mL for α-glucosidase
0.210 mg/mL for pancreatic lipase
These were significantly stronger than those of Sargassum fusiforme alone, indicating a synergistic enhancement after combination.
4 Discussion
Each of the three active ingredients possesses recognized hypoglycemic and hypolipidemic effects, and the composite formula demonstrates synergistic activity. The optimized natural formulation is safe and shows strong potential for development into functional foods aimed at blood glucose and lipid regulation. However, further in vivo studies and adherence to regulatory requirements are needed for future product development.
