Formulation of a stable water-in-oil nanoemulsion rich in anti-diabetic components of the roselle extract for controlled release

Abstract

Hibiscus sabdariffa Linn. (Roselle) is a good source of the anti-diabetic agents like cyanidin-3-sambubioside, delphinidin-3-sambubioside, and delphinidin-3-glucoside. However, their rapid degradation nullifies their maximal dosage delivery to the human body to adequately impart their therapeutic benefits. Hence, this work aimed to improve the absorption of anti-diabetic components in the Hibiscus sabdariffa Linn (roselle) extract through oral consumption of a w/o nanoemulsion prepared using an integrated low-energy phase inversion and high-energy ultrahomogenization method. The water-in-oil nanoemulsions (w/o) were screened to identify the optimal condition for preparing stable nanoemulsions with the lowest mean droplet size (MDS) of < 150 nm. The best nanoemulsion composition yielded a MDS and polydispersity index of 133.6 nm and 0.165, respectively. The low conductivity (5 µScm-1) alongside the absence of phase separation under an accelerated stability study (centrifugal force and freeze–thaw cycles) and storage (4, 25, and 40 °C) for up to 71 days verified the w/o nanoemulsion’s identity and its shelf-life stability. The abovementioned data collectively verified the stability of the roselle extract w/o nanoemulsion. The first two-hour in vitro release study showed the liberation of 85% and 60% of the bioactive ingredients at pH 6.8 and pH 2.5, respectively. The latter’s nonlinear release kinetics indicated a longer residence time that supported a more gradual release of the active ingredients. This is the first report detailing the preparation of an orally consumed roselle extract w/o nanoemulsion as an anti-diabetic agent. The formulated w/o nanoemulsion was suitable for the gradual release of the anti-diabetic agents through the simulated gastrointestinal tract.