Hemp Seed Hull Powder: A Sustainable Source of Bioavailable Micronutrients and Phytochemicals with Inhibitory Activity Against α-Amylase and α-Glucosidase

Hemp seed hulls are a by-product of hemp seed dehulling and may serve as a valuable functional powdered food ingredient. To date, hemp hulls studies focus on total phenolic content, α-amylase inhibition, and gut microbiota. To revalorize the powder, a comprehensive understanding of the gastrointestinal metabolism of its individual nutrients and plant metabolites, as well as of its potential to modulate other digestive enzymes, such as α-glucosidase, is required. This study assessed the suitability of hemp seed hull powder as a food ingredient by evaluating in vitro digestion and microbial metabolism (in vitro) of its nutrients and phytochemicals, as well as its potential to inhibit α-amylase and α-glucosidase activities. Minerals, potassium (76.29%), phosphorus (73.11%), and magnesium (64.11%) showed the highest bioaccessibility following in vitro digestion. In vitro digestion led to an increase in bound phytochemical levels. Salicylic acid was the most abundant metabolite available for absorption in the small intestine. Insoluble non-starch polysaccharide (NSP) content was positively associated with propionate and butyrate following microbial fermentation. Indole-3-pyruvic acid, phenylacetic acid, which are beneficial metabolites, increased during microbial fermentation of hemp seed hull powder. In addition, compared to the control, the hemp seed hull powder resulted in higher phenol and lower levels of the deleterious metabolite, p-cresol. The hemp seed hull powder extract (free phytochemicals) exhibited lower inhibitory potential against α-amylase (p < 0.01) but greater inhibitory potential against α-glucosidase compared with acarbose. These results strongly support the importance of hemp seed hull powder as a sustainable ingredient for functional food applications.