Development and Characterization of Ksheerabala Oil Nanoemulgel: A Novel Approach for Topical Ayurvedic Medicine

Herbal and Ayurvedic formulations continue to attract scientific attention due to their long-standing therapeutic use and potential for safe, holistic treatment. Ksheerabala oil is a classical medicated preparation known for its anti-inflammatory and neuroprotective benefits, yet its topical application is limited by poor skin permeation, greasiness, instability, and low patient acceptability. These drawbacks reduce its effectiveness in delivering actives to the target site.

Novel drug delivery systems, particularly nanoemulgels, offer a promising solution to enhance topical delivery of traditional oils. Nanoemulgels combine the high solubilization and improved skin penetration of nanoemulsions with the favorable spreadability and non-greasy nature of hydrogels. Such systems can enhance permeation, stability, aesthetic appeal, and overall therapeutic performance. (Figure 1).

The present study focuses on developing and characterizing a nanoemulgel of Ksheerabala oil through systematic formulation and evaluation, including physicochemical analysis, in-vitro permeation using Franz diffusion cells, and stability testing. This work aims to modernize a traditional Ayurvedic medicine and support its integration into evidence-based topical drug delivery.

EXPERIMENTAL:

MATERIAL USED

Ksheerabala oil was procured from a certified Ayurvedic pharmacy (Sumveds, India) and stored in amber glass containers to prevent photodegradation. Tween 80, polyethylene glycol (PEG 400), Carbopol 940, triethanolamine (TEA), and preservatives (methylparaben and propylparaben) were of pharmaceutical grade. All other chemicals and solvents were analytical grade. Purified water (Type I) was used throughout the study.

INSTRUMENTS USED

An analytical balance (Essae Vibra) was used for precise weighing, and pH was measured using a digital pH meter (Eutech). A probe sonicator (Vibra-Cell), magnetic stirrer (Remi), and vortex mixer (Spinix) assisted in formulation processing. An ultracentrifuge (Remi) was used for sample separation. Viscosity was evaluated using a Brookfield viscometer, and FTIR analysis was performed on a Shimadzu spectrophotometer. Globule size, PDI, and zeta potential were measured using a Malvern Zetasizer, and permeation studies were conducted using a Franz diffusion cell system.

Physicochemical Evaluation of Ksheerabala Oil

Acid value, saponification value, and ester value were determined using standard titrimetric methods. Acid value was measured by titration of the oil sample with 0.1 N KOH using phenolphthalein as an indicator. Saponification value was determined by refluxing the oil with ethanolic KOH followed by back-titration with HCl. Ester value was calculated as the difference between the saponification and acid values.

Construction of Pseudo-Ternary Phase Diagrams

To identify the self-emulsifying region, pseudo-ternary phase diagrams were constructed using Ksheerabala oil (oil phase), Tween 80 (surfactant), PEG 400 (co-surfactant), and water. Surfactant–co-surfactant mixtures (Smix) were prepared in ratios of 1:1, 1:2, 1:3, 2:1, and 3:1 (v/v). For each Smix ratio, oil and Smix were mixed in varying proportions and titrated with water under gentle stirring. Transparent and stable nanoemulsion regions were visually identified and plotted using TernaryPlot software.

Preparation of Nanoemulsion

An optimized composition from the nanoemulsion region was selected. The oil phase (Ksheerabala oil + Smix) was gradually added to the aqueous phase under magnetic stirring (1000–1500 rpm, 30–40 min) to form a coarse emulsion. The mixture was subjected to probe sonication (20 kHz, 10–15 min) to reduce droplet size and obtain a transparent nanoemulsion. Formulations were stored in amber vials for further use.

Figure 2: Pseudoternary phase diagram of optimized formulation

Table 1: Data of optimized formulation

Preparation of Nanoemulgel

Gel Base Formation - Carbopol 940 (0.24–1.5% w/w) was dispersed in water and allowed to hydrate overnight. The dispersion was neutralized with TEA to achieve pH 6.5–7.0, forming a clear gel.

Incorporation of Nanoemulsion

The optimized nanoemulsion was slowly incorporated into the gel base with continuous gentle stirring to obtain a homogenous nanoemulgel. Air bubble entrapment was minimized by low-speed homogenization (800–1000 rpm, 15 min). The final formulation was stored in airtight containers.

Characterization of Nanoemulsion and Nanoemulgel

Physical Appearance and pH

Formulations were inspected for clarity, color, homogeneity, and phase separation. pH was measured by dispersing 1 g of sample in 10 mL of water using a calibrated pH meter.

Viscosity

Viscosity was determined using a Brookfield viscometer (spindle 64) at 25 ± 1°C at multiple shear rates (10–100 rpm).

Spreadability

Spreadability was evaluated using a glass slide method. A 500 g weight was placed on a sample sandwiched between two slides for 1 min, and the spread diameter was recorded.

Spreadability (S) was calculated using:

S = M × L / T

Globule Size, PDI, and Zeta Potential

Nanoemulsion droplet size, polydispersity index (PDI), and zeta potential were measured using Dynamic Light Scattering (DLS) on a Zetasizer instrument. Samples were diluted appropriately prior to analysis.

FTIR Analysis

FTIR spectra (4000–400 cm?¹) were recorded to evaluate potential interactions between Ksheerabala oil and excipients.

In Vitro Drug Release Study

In vitro release was performed using Franz diffusion cells with a dialysis membrane (MWCO 12–14 kDa). The receptor compartment contained phosphate buffer (pH 7.4) maintained at 37 ± 0.5°C and stirred at 600 rpm. One gram of nanoemulgel was placed in the donor compartment. Samples (1 mL) were withdrawn at predetermined intervals (0.5–8 h) and replaced with fresh buffer. Samples were filtered through a 0.22 μm membrane and analyzed for drug content.

Stability Studies

Stability was assessed according to ICH Q1A(R2) guidelines. Formulations were stored at:

• 4 ± 2°C
• 25 ± 2°C / 60 ± 5% RH

Evaluations were performed at 0, 30, 60, and 90 days. Parameters monitored included appearance, pH, viscosity, homogeneity, and phase separation.

RESULT AND DISCUSSION:

Physicochemical Evaluation of Ksheerabala Oil

The physicochemical properties of Ksheerabala oil were assessed to establish its suitability for nanoemulgel formulation. The acid value (33.9 mg KOH/g) indicated a moderate level of free fatty acids, consistent with herbal oils stored under controlled conditions and acceptable for external application. The saponification value (196.35 mg KOH/g) suggested a predominance of short- to medium-chain fatty acids, which is favorable for enhanced skin absorption and emulsification efficiency. The resulting ester value (162.45 mg KOH/g) confirmed that most fatty acids remained in esterified form, indicating minimal degradation and good oil integrity. These findings support the oil’s stability and compatibility with nanoformulation approaches.

Physical Appearance

The optimized nanoemulgel exhibited a translucent, pale-yellow appearance with smooth, uniform consistency and no signs of phase separation, creaming, or precipitation. Its non-greasy texture and ease of spreadability indicated successful incorporation of the nanoemulsion into the gel matrix. The visual stability throughout the study confirms good compatibility between Ksheerabala oil, surfactant–cosurfactant mixture, and Carbopol 940.

pH Measurement

The nanoemulgel showed a pH range of 5.42–5.46, which falls within the physiologically acceptable limits for topical applications (pH 5.5–7.0). This slightly acidic pH supports skin compatibility and minimizes irritation risk. The formulation maintained stable pH values during stability testing, indicating chemical stability under storage conditions.

Figure 3: pH characterization

Viscosity and Rheological Behavior

Viscosity measurements (6,254–57,564 cps) demonstrated pseudoplastic, shear-thinning behavior, characteristic of topical semisolid preparations. This rheological profile ensures easy spreading upon application while maintaining structural integrity afterward. The results align with literature reports of Carbopol-based nanoemulgels exhibiting non-Newtonian flow properties, supporting user-friendly application and retention on the skin.

Figure 4: pH characterization

Spreadability

The spreadability value of 28 ± 1.3 g·cm/s indicated good extensibility and effortless dispersion across surfaces. Efficient spreading ensures uniform drug distribution, improves patient experience, and enhances therapeutic coverage. The balance between viscosity and spreadability reflects an optimized formulation suitable for topical delivery.

Figure 5: Spreadability characterization

Globule Size, PDI, and Zeta Potential of Nanoemulsion

The average droplet size of the incorporated nanoemulsion was 177.5 nm, confirming successful nano-sizing and supporting enhanced permeation through the stratum corneum. The PDI value of 0.258 indicated a narrow size distribution and uniform droplet population, ensuring long-term physical stability. The zeta potential of −36.8 mV suggested strong electrostatic repulsion between droplets, minimizing aggregation and contributing to colloidal stability. These results collectively indicate that the optimized nanoemulsion system is robust and well suited for gel incorporation.

Figure 6: Graph of Globule Size Analysis

FTIR Analysis

FTIR spectra of Ksheerabala oil, Carbopol 940, nanoemulsion, and the final nanoemulgel showed the retention of major characteristic peaks (e.g., O–H, C–H, and C=O stretching). The absence of significant peak shifts or disappearance indicates no chemical incompatibility between the drug and excipients. The masking of Ksheerabala oil peaks within the nanoemulsion and nanoemulgel spectra suggests successful entrapment of the oil within the formulation matrix.

Figure 7:  FTIR of Ksheerabala oil

Figure 8:  FTIR of Carbopol 940

Figure 9:  FTIR of Nanoemulsion

Figure 10:  FTIR of Nanoemulgel

In Vitro Drug Release Study

The nanoemulgel displayed sustained drug release over 8 hours, consistent with a controlled topical delivery system. Release kinetics followed the Korsmeyer–Peppas model, suggesting a combination of diffusion and polymer relaxation mechanisms. The improved release profile can be attributed to the nano-sized droplets enhancing surface area for diffusion and the gel matrix regulating release. These observations correlate with reports of herbal nanoemulgels exhibiting superior release behavior compared to conventional gels.

Table 2: Calibration curve data

Figure 11:  Calibration curve of Palmitic acid

Table 3: Permeation study data

Stability Studies