Black cumin (Nigella sativa) oleosome as a natural delivery system for curcumin: characterization, preparation, and in vitro digestive behavior

Oleosomes, also known as oil bodies (OBs), are naturally occurring colloidal particles present in edible plant seeds and nuts and possess unique functional properties. In this study, oleosomes derived from black cumin (BCO) were extracted and used as novel, natural carriers for the encapsulation of hydrophobic compounds, using curcumin as a model bioactive. An optimized extraction method achieved a satisfactory recovery yield of approximately 38%, and the physicochemical characteristics of black cumin oleosome (BCO) and its associated proteins were systematically characterized. Curcumin is an unstable bioactive compound of turmeric with high sensitivity to degradation and metabolism, which needs to be encapsulated and protected within a matrix. Curcumin was well encapsulated into BCO using a different pH-shift method, resulting in a high encapsulation efficiency of 91%, without precipitation of curcumin, which was consistent with the FT-IR results, indicating that 10 mg of curcumin was successfully encapsulated within the interior core of oleosomes. Curcumin-loaded oleosomes demonstrated improved functional performance, including enhanced antioxidant stability and emulsifying properties. In vitro gastrointestinal digestion studies revealed a cumulative curcumin release of 64% by the end of the intestinal phase, confirming the effectiveness of the pH-shift encapsulation method and the black cumin oleosome as a vehicle for delivering curcumin and increasing its bioavailability. Overall, these findings indicate that curcumin could be well encapsulated within naturally derived oleosomes via a novel pH-shift method and black cumin oleosomes are effective carriers for enhancing the delivery of hydrophobic nutraceuticals via oral routes, which shows strong potential for incorporation of oleosomes into existing food formulations or for the development of novel functional food products.