Hempseed proteins: a source of bioactive peptides

Hemp, the non-drug variety of Cannabis sativa L., is a widely cultivated plant of industrial interest as an important source of food, fiber and bioactive phytochemicals (Callaway, 2004). Hempseed, a by-product of hemp fiber production, contains over 30% oil and about 25% protein of high quality. It has potential applications in nutraceutics, since its hydrolysis can produce bioactive peptides having, for example, antioxidant, and hypotensive activity (Girgih et al., 2014). The last one is often related to the inhibition of angiotensin I converting enzyme (ACE), the main enzyme involved in human blood pressure control pathway through renin-angiotensin system. Some ACE inhibitory peptides have been already identified in hempseed protein hydrolysates obtained with pepsin and pancreatin (Girgih et al., 2014). In this work, hempseed protein isolate, prepared from defatted hempseed meals by alkaline solubilization/acid precipitation, was subjected to extensive chemical hydrolysis under acid conditions (6M HCl). The resulting hydrolysate was fractionated by reverse-phase preparative HPLC and single fractions were tested for ACE-inhibition activity (Boschin et al., 2014). LC-MS and mono- and bi-dimensional NMR analysis of the most promising ones led to the identification of a number of potential bioactive peptides composed of three-five residues. In order to determine the actual amino acid sequences responsible for the observed enzyme inhibitory properties, such peptides will be prepared by solid-phase synthesis, taking also into account the primary sequence of hemp seed protein, and further tested for ACE-inhibitory activity.