Development and assessment of stable formulations containing two herbal antimicrobials: Allium sativum L. and Eruca sativa miller seed oils.

Context: Garlic oil and Eruca oil have been reported to have excellent antimicrobial activity. However, the exact knowledge of their required hydrophilic-lipophilic balance (rHLB) values to facilitate their emulsification are still not reported in the literature.

Objective: The objective of this study is to determine rHLB values of Garlic and Eruca oils to formulate an elegant stable cream formulation enriched with both oils.

Materials And Methods: Emulsions of both oils were prepared by the bottle method using water, Tween 80 and Span 80. Formulated emulsions were evaluated for creaming index (CI), droplet size, and turbidity to determine rHLB. Utilizing determined rHLB, creams were formulated using a combination of two surfactants, Span 60:Brij 58 (1:2.333) at three different concentrations (2, 4, and 6%).

Results: rHLB of Garlic oil and Eruca oil was determined to be 7.92 ± 0.27 and 9.76 ± 0.32, respectively. Stable cream (F1) developed with 2% surfactant blend showed elegant rheological properties, the best antimicrobial activity against Staphyococcus aureus ATCC29737, Escherichia coli ATCC25299 S. aureus (MRSA), Malassezia fufur AUMC No. 5173 with no skin irritation. In addition, its texture parameters and pH were found to be consistent over 12 months at 25 ± 1 °C and 60% relative humidity.

Discussion: The lowest CI, smallest droplet size, and highest turbidity were obtained at the optimum surfactant concentration in the prepared emulsions. Increasing surfactant blend concentration in cream formulations leads to increasing viscosity and consequently decreasing antimicrobial activity.

Conclusion: Determination of the rHLB of Garlic and Eruca oils allows the ease of preparation of stable, consistent, and non-irritant cream.