Anti-diabetic activity of phlorotannin from Eisenia bicyclis in Zebrafish, a model of type 1 and 2 diabetes

Eisenia bicyclis (Kjellman) Setchell is an edible perennial brown alga in the family Lessoniaceae and is widely distributed in the coastal area of Ulleung and Jeju islands in Korea, and in Japan [1, 2]. Previous studies on E. bicyclis, have investigated several biological activities including anti-inflammation, antioxidative, and neuroprotective effects. In continuation of our search for anti-diabetic compound from natural products, we have found that the EtOH extract of E. bicyclis has antihyperglycemic activity in the zebrafish model for type 1 and 2 diabetes. Type 1 diabetes zebrafish model was induced by alloxan, which cause pancreatic β-cell necrosis [3]. In addition, type 2 diabetes zebrafish model was induced by insulin. Exposure to excess insulin can induce insulin resistance typical of type 2 diabetes [4]. Following alloxan or insulin treatment, pancreatic islet size and fluorescence intensity were measured. The EtOH extract was consecutively partitioned with CH₂Cl₂, EtOAc and n-BuOH to give four fractions. Among these fractions, the EtOAc fraction which showed antihyperglycemic activity was subjected to activity-guided fractionation and isolation. Three phlorotannins, eckol, dieckol and phlorofucofuroeckol-A, were isolated from the EtOAc fraction. The isolated compounds revealed anti-diabetic activity for type1 and 2 in the zebrafish model.

References:

[1] Boo SM, Ko YD. Marine Plants from Korea. Seoul: Junghaeng-Sa; 2012; 119

[2] Kwon T-H et al. Antioxidant activity of various solvent fractions from Edible brown alga, Eisenia bicyclis and Its Active compounds. J Food Sci 2013; 78: C679 – 684

[3] Desgraz R et al. β-Cell regeneration: the pancreatic intrinsic faculty. Trends Endocrin Met 2011; 22: 34 – 43

[4] Yang X et al. Exposure to excess insulin (glargine) induces type 2 diabetes mellitus in mice fed on a chow diet. J Endocrinol 2014; 221: 469 – 480