Tamarindus indica sub-products as potential tools for simultaneous management of diabetes and obesity†

Aiming at valorizing industrial wastes of tamarind, the present work evaluated the actions of seed, leaf and peel extracts on starch and fat absorption through starch and triglyceride tolerance tests in mice. The actions of all extracts on the α-amylase and lipase were also characterized using classical kinetic assays. All extracts inhibited starch digestion in vivo, but the seed extract was the most effective one with an ID₅₀ of 151.4 mg kg⁻¹. The mechanism behind this inhibition probably involves the pancreatic α-amylase, which was strongly inhibited by the seed extract under in vitro conditions (IC₅₀ = 13.3 μg mL⁻¹) and much less strongly by the leaf and peel extracts (IC₅₀ values in the vicinity of 400 μg mL⁻¹). The pancreatic lipase, conversely, was inhibited solely by the seed extract, with an IC₅₀ of 31.5 μg mL⁻¹. As a consequence of this property, the seed extract also inhibited triglyceride absorption, as indicated by olive oil tolerance tests, which revealed an ID₅₀ of 214.9 mg kg⁻¹. The seed extract also possessed the strongest antioxidant capacity and the highest content in phenolic groups. Chemical analyses revealed that all extracts present a great variety of phenolic compounds and that the seed extract possesses at least 5 unique compounds (ursodiol, masoprocol, lenticin, chenodeoxycolic acid and 13-keto-9Z,11E-octadecadienoic acid), which, according to docking studies, could be involved in the inhibition of both α-amylase and lipase. The overall conclusion is that the tamarind seed extract displays great potential for being used in the management of obesity and diabetes.