Potential of siphonaxanthin, a green algal carotenoid, to prevent obesity and related diseases.

The increasing prevalence of obesity and its related diseases, including diabetes mellitus and metabolic dysfunction-associated fatty liver disease, has become a significant social problem. These diseases are believed to be preventable through healthy diet and exercise habits, and the investigation of food ingredients that are useful for prevention of these diseases is actively ongoing. Carotenoids are the major lipophilic pigments responsible for yellow-to-red colors in our diet, and the ingestion of certain carotenoids has been reported to prevent obesity. For example, β-carotene suppresses adipogenic differentiation of mouse preadipocyte line 3T3-L1 through its provitamin A activity. Fucoxanthin, a carotenoid found in brown algae, also has the similar effect via a different mechanism and is used as an active ingredient in foods with functional claims in Japan. In contrast, siphonaxanthin, a carotenoid found in some green algae such as Caulerpa lentillifera (commonly known as sea grape), exhibited stronger biological activities than other carotenoids in cell-based studies; it significantly suppressed adipogenic differentiation of 3T3-L1 cells even at low concentrations where β-carotene and fucoxanthin did not show inhibitory effects. However, its practical applications have not yet been realized. This review summarizes the studies on the anti-obesity effects of carotenoids and discusses the potential of siphonaxanthin as a novel functional food ingredient.