Formulation, Optimization, and Evaluation of Nigella sativa Nanoemulsion for Diabetes Mellitus

Abstract

Background: Therapeutic potential of polyherbal formulations is often limited by poor solubility and bioavailability. This study aimed to develop and optimize a Polyherbal Nanoemulsion using the spontaneous emulsification method to enhance drug encapsulation and improve release characteristics.
Methods: Box-Behnken Design (BBD) was employed to optimize critical formulation parameters, including Black Seed Oil concentration, Smix ratio, and aqueous phase volume. The nanoemulsion was characterized for particle size, encapsulation efficiency, and in vitro drug release, In vitro anti-diabetic activity was evaluated using α-amylase and α-glucosidase inhibition assays to compare the efficacy of the nanoemulsion with a standard drug (Acarbose). ANOVA and response surface analysis were conducted to assess the impact of formulation variables. Predicted and experimental values were compared to validate the optimization model.
Results: Optimized formulation exhibited an encapsulation efficiency of 93.83 ± 1.4, particle size of 183.14 ± 0.8 nm, and cumulative drug release of 79.76 ± 1.7 closely matching the predicted values (176.5 nm, 92.9%, and 77.8%, respectively). Encapsulation efficiency ranged between 83.9%–93.2%, while particle size varied from 176–224 nm. In vitro release studies confirmed an improved drug release profile, with 3D surface response and ANOVA analysis highlighting the significant influence of formulation factors on nanoemulsion properties. In vitro anti-diabetic studies showed that the Polyherbal Nanoemulsion exhibited α-amylase inhibition of 72.5 ± 2.1% and α-glucosidase inhibition of 68.9 ± 1.8%, demonstrating comparable efficacy to Acarbose (80.2 ± 1.5% and 76.4 ± 1.2%, respectively).
Conclusion: Polyherbal Nanoemulsion demonstrated enhanced encapsulation efficiency and improved drug release compared to conventional formulations. The strong correlation between predicted and experimental values validates the optimization approach, indicating that this nanoemulsion system is a promising strategy for improving the bioavailability of polyherbal formulations.