Diabetes mellitus (DM) is becoming increasingly prominent, posing a serious threat to human health. Its prevalence is rising every year, and often affects young people. In the past few decades, research on marine algae has been recognized as a major field of drug discovery. Seaweed active substances, including algal polysaccharides, algal polyphenols, algal unsaturated fatty acids, and algal dietary fiber, have unique biological activities. This article reviews the effects and mechanisms of the types, structures, and compositions of seaweed on inhibiting glucose and lipid metabolism disorders, with a focus on the inhibitory effect of active substances on blood glucose reduction. The aim is to provide a basis for the development of seaweed active substance hypoglycemic drugs.

Oxidative stress is related to cellular damages and aging. Bioactive peptides have the potential to be a useful functional ingredient, although Bangia fuscopurpurea (red alga), a dense protein source, has not yet been exploited as a source of antioxidant peptide. The aim of the study was to prepare, isolate, and characterize antioxidant peptide of B. fuscopurpurea and assess their protection against oxidative stress in vitro, in HepG2 cells, and in Caenorhabditis elegans. Protein of B. fuscopurpurea was subjected to hydrolysis with papain and purification of the hydrolysate was performed through multi-step chromatography and ultrafiltration. The LC-MS/MS identified peptides, which were synthesized and screened. Two new peptides, YPCW and GYPYK, were discovered and both of them had strong antioxidant properties in vitro, with the ABTS radical scavenging IC₅₀ of 2.52 ± 0.37 µg/mL and ORAC of 5187 ± 78 µmol TE/g. Both peptides in H₂O₂-induced HepG2 cells significantly decreased the intracellular ROS and MDA and inhibited the activity of antioxidant enzymes (SOD, CAT, and GSH-Px). Moreover, YPCW and GYPYK increased the survival of C. elegans during oxidative stress and the similar response, altering antioxidant enzyme activities in vivo and MDA levels. These findings indicate that peptides obtained through B. fuscopurpurea can be useful as antioxidant agents, and they can be considered as a possible new active ingredient of functional foods or pharmaceuticals to counteract oxidative stress.