Enhanced extraction of ashwagandha antioxidants using response surface methodology and their stabilization in O/W emulsions: A study with reference to glucose modulation

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This study investigated the optimization of extraction conditions for formulating oil-in-water (O/W) emulsions to encapsulate ashwagandha, with a focus on enhanced antioxidant activity and glucose-modulatory potential. The Box-Behnken design using response surface methodology was employed to evaluate four independent variables with different levels, including stirring time (10-30 min), temperature (40-60°C), ultrasonication power (50-90%), and ashwagandha to oil ratio (1-10% (w/w)). The extract prepared with optimized extraction conditions was used to formulate O/W emulsions with varying concentrations of decaglycerol monolaurate (5, 7, and 10% (w/w)) as a hydrophilic emulsifier. The fitted models generated for all responses were statistically significant ( p < 0.05) with a non-significant lack of fit ( p > 0.05). The TPC ranged from 53.76 to 146.28 mg GAE/g, TFC ranged from 3.96 to 85.83 mg QE/g, DPPH ranged from 20.93 to 74.17%, FRAP ranged from 53.49 to 172.49 mg TE/g, and ABTS ranged from 34.51% to 108.63%. Optimization of these extraction parameters yields the optimal conditions: 24 min of stirring, 45°C, 90% ultrasonication power, and a 10% (w/w) ashwagandha-to-oil ratio. Furthermore, in subsequent biological evaluation, the optimized extract demonstrated significant in vitro enzyme inhibition, with 77% α-amylase and 67.7% α-glucosidase inhibition, suggesting its carbohydrate-hydrolyzing modulation potential. The 7% (w/w) decaglycerol monolaurate was identified as optimal for superior stability and significant biological activity. The volume mean diameter ( d 4,3 ) was 0.6 μm with a span factor of 0.598, indicating a uniform and stable droplet distribution. Further testing confirmed that the O/W emulsions remained stable across various pH levels with no phase separation. It remained sensitive to salt stress and showed significant time-dependent degradation during the 30-day storage study. These findings provide valuable information in designing nutritional products aimed at glucose modulation.