Optimization and Characterization of Self Nano Emulsifying Drug Delivery System loaded with 18- β Glycerrhetinic acid

The purpose of this study was to prepare, optimize and evaluate self nano emulsifying drug delivery system (SNEDDS) containing 18β glycerrhetinic acid which enhances the dissolution profile or bioavailability of the drug in comparison to pure suspension of 18β glycerrhetinic acid.18β glycerrhetinic acid loaded SNEDDS having geranium oil as oil phase, tween 80 as a surfactant, and dimethyl sulfoxide (DMSO) as co-surfactant were prepared using pseudo ternary phase diagram and Box-Behnken experimental design was used to optimize the different formulations. Optimized formulations were characterized for self-emulsifying time, globule size, zeta potential, and drug release. The mean droplet size and PDI of the optimized formulation were found to be in a variation of 93.42 nm and 0.401 respectively. FTIR data showed no physicochemical interaction between excipients and drug. The encapsulation efficiency of optimised 18β glycerrhetinic acid SNEDDS was found 80.12±1.52% , % transmittance was found 99.34±0.134% and the viscosity of all the formulations was found 0.8872 cp. Three-dimensional response surface plots and two-dimensional contour plots of the responses across the selected factors were constructed that explained the relationship between the independent and dependent variables. Release kinetics was calculated by using KinetDS3.0. It was concluded that prepared formulations were formulated with approximately desired mean droplet size confirmed by BoxBehnken experimental design as well as properly optimized and characterized. Original Research Article Farooqui; JPRI, 33(59A): 304-324, 2021; Article no.JPRI.78603 305


INTRODUCTION
Recently, an active pharmaceutical ingredient derived from natural origin has drawn attention in the pharmaceutical field day by day. Researchers, put more attention to planning novel dosage forms with these phytochemicals as they have high biological activity, satisfactory clinical efficacy, and low toxicity [1]. 18-β glycerrhetinic acid is separated from glycyrrhizaglabra roots (liquorice) belonging to the family Fabaceae, which is widely used as an herbal medicine for many years. 18-β glycerrhetinic acid shows many pharmacological effects, such as antimicrobial, antiulcer, immunemodulatory, anti-inflammatory, anti-tussive, and antiviral [2]. It also controls and prevents various skin inflammation diseases, such as atopic dermatitis and UV-induced skin photo-aging. From the literature review, it was studied that 18β glycerrhetinic acid is having biopharmaceutical classification system (BCS) class II, which shows low solubility and high permeability but, although having high permeability properties, these class II drugs have limited bioavailability because of low dissolution rate [3,4]. It was found in studies that drugs to be absorbed or diffusion through membranes was to be first dissolved in the physiological medium. Since these drugs are having poor solubility in media, so they cannot be absorbed properly, this results in poor bioavailability. Owing to the high permeation property, it cannot transport them to the membrane because of poor solubility in aqueous media [5]. So in this research article, SNEDDS were designed with aim to deliver topically. SNEDDS are isotropic mixture thermodynamically stable solutions of drug, oil, surfactant, and co-surfactant which, upon small agitation, generate fine droplets of water-in-oil nanoemulsions [6]. They require very low free energy for the self nano emulsification process. In this study, SNEDDS were used as the ideal carrier for the delivery of these phyto-chemical drugs for enhancing their activity and efficacy [7].
This study was performed to develop SNEDDS having 18-β glycerrhetinic acid as a natural origin drug to show in-vitro antioxidant effect and in vivo anti-inflammatory effect and hair growthpromoting effect during animal studies in further research work that is not included in this paper. The components of 18-β glycerrhetinic acid-SNEDDS were geranium oil, tween 80, and DMSO.
Phase diagrams were shown for identifying the emulsification region. 18-β Glycerrhetinic acid is characterized as a broadspectrum drug [8]. 18-β glycerrhetinic acid inhibits the formation of dihydrotestosterone (DHT), which is an androgen that is a sex hormone that contributes to the development of hair in males [9].
The most liked design of experiment for response surface studies is the Box-Behnken design applied to optimize SNEDDS loaded with 18-β glycerrhetinic acid. Box-Behnken design is used to identify a relationship between response variables as dependent factors and quantitative experimental parameters as independent factors. The design needs three independent factors that comprise three levels. Box-Behnken design is selected because it requires fewer runs and has three-level factorial designs. That is why it is to be considered more efficient than other computational designs [10]. Compared to other response surface method designs, Box-Behnken designs require a few runs that are 13 runs in a 3-factor experimental design. That is why Box-Behnken design was applied to optimize SNEDDS of 18-β glycerrhetinic acid. The independent variables were selected as the amount of oil (geranium oil, X1), amount of surfactant (tween 80, X2), and amount of cosurfactant (DMSO, X3). The dependent variable has globule size in nanometer (Y1), self emulsification time in sec. (Y2) and percentage drug release after 12 hours (Y3) [11]. In this study, mathematical model equations from computer simulation programming of Design Expert trial version 12 software for optimizing SNEDDS of 18-β glycerrhetinic acid was derived [12]. The physicochemical characterization studies were done by using zetasizer, Fourier transform infrared spectroscopy (FTIR) [13].

Optimising diffusion rates of drug
An approach for optimizing the diffusion rate of drugs from a vehicle based on the relative polarity index or log P of the drug to the log P of the stratum corneum, a value called the penetrant polarity gap (PPG). They estimate the log P of the stratum corneum to be 0.8 and use this value along with the log P of the drug to calculate the PPG: Penetrant polarity gap = PPG = log P penetrant log-P stratum corneum. The relative polarity of the phase of the formulation in which it dissolved the active ingredient should be the magnitude of the PPG greater or less than the log P of the active ingredient [14].

Solubility studies
The selection of oil, surfactant, and co-surfactant is done by dissolving an excess amount of the drug. Various oil, surfactant, and co-surfactant were taken such as geranium oil, bottle guard oil, arachis oil, lemon grass oil, span 20, span 80, tween 40, tween 80, gelucire, and DMSO were screened on solubility bases using the shake flask method. In this method, excess quantity (1g) of 18-beta-glycerrhetinic acid was dissolved in each test tube having 2 ml of excipients (oil, surfactant, and co-surfactant). These mixtures were thoroughly mixed with a vortex shaker at 37 0 C. The mixture is kept for 24 h and centrifuged using a high centrifuge at 6000 rpm for 20 min. The supernatant was separated and after suitable dilution with methanol, the drug concentration was analyzed by using U-V Visible spectrophotometer (UV-1800, Shimadzu Corporation, Tokyo, Japan) at wavelength 267 nm [11].

Partition coefficient
By shake flask method: An excess amount (100mg) of the drug was dissolved in a separating funnel in octanol (50ml) and water (50ml). The shaking was done vigorously and kept to settle for 24 hrs after it, two phases were separated into separate beakers and further dilutions of water phase were done by pipette out 1ml in 100ml volumetric flasks, then absorbance was determined by UV Shimadzu 1800 [14].
Then the concentration of the drug was calculated by putting the absorbance value in the standard curve equation, i.e. y = mx + c So by applying the formula,

U.V. Characterization of drug
A standard stock solution of 18-β glycerrhetinic acid was prepared by dissolving 10 mg of drug in 100 ml in phosphate buffer [pH 6.8]: methanol in 70: 30 proportion to make 100µg/ml from this pipette out 2ml, 4ml, 6ml, 8ml, and 10ml make up with phosphate buffer in 100 ml volumetric flask to make dilutions of 2µg/ml, 4µg/ml, 6µg/ml, 8µg/ml and 10µg/ml then absorbance was taken at λ 267nm [6].

Fourier transformed infrared spectroscopy (FTIR)
Fourier transformed infrared spectroscopy (FT-IR) of pure drug, a combination of pure drug and oil, a combination of a drug with surfactant and co-surfactant, and physical mixture (drug, oil, surfactant and cosurfactant) were carried out using KBr disc. The spectral using Fourier transform infrared spectrophotometer (Shimadzu Corpn., Japan, IR Prestige 21) that scanned each KBr disc at 4 mm/s at a resolution of 2 cm over a wave number region of 4000-400 cm −1 were recorded. Both FTIR of plain drug and drug with oil, surfactant, and co-surfactant was carried out [15].

Construction of pseudo ternary phase diagram
The pseudo ternary phase diagrams were constructed for the identification of the concentration range of components for the formulation of nanoemulsions. The optimal concentration of oil, surfactant, and co-surfactant was determined by this for the formulation of SNEDDS. They constructed all the components to w/w %. The construction of pseudo ternary phase diagrams without incorporating drugs with the help of an online ternary plotter. The darker region in the phase diagram shows the selfemulsification area. Fig. 4 represents the phase diagram having geranium oil (oil), tween 80 (surfactant), and DMSO (co-Surfactant) at the apex of the ternary diagram. Surfactant and cosurfactant mixture (Smix) were taken in different volume ratios that is (1:1, 1:2, 2:1). Each phase diagram was constructed by mixing oil and S mix in the ratio (9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9). The ternary mixture of oil, surfactant, and co-surfactant was blended with a vortex shaker. 0.5 ml of the ternary mixture was taken and diluted to 500 ml distilled water in the beaker was gently stirred on the mechanical shaker while maintaining the temperature at 37 0 C. Emulsification takes place spontaneously and is investigated for the spreading of its droplets. This emulsion was kept on rest for 3 hrs and its transmittance was assessed by using a UV-Visible spectrophotometer (UV-1800, Shimadzu Corporation, Tokyo, Japan) at wavelength 267nm [16].

Box-Behnken Experimental Design
Three factors, three levels (3 3 ) Box-Behnken experimental design was produced by using design experiment 12 software [17,18] was employed to plan liquid SNEDDS. The concentration of oil (geranium oil, X1), surfactant (Tween 80, X2), and co-surfactant (DMSO, X3) were taken as independent variables which have globule size (Y1) in nanometer, selfemulsification time (Y2) in seconds, and drug release (Y3) in percentage as shown in Table 1. This experimental design is a suitable approach for studying the effects of independent variables and their effect associated with dependent variables. The level of surfactant, co-surfactant, and oil was taken in a range of (16-60% w/w), (10-90% w/w), and (05-40% w/w), respectively. Weighed amount (50mg) of 18-β glycerrhetinic acid was mixed first with oil after followed by the addition of a proper amount of surfactant. After proper mixing, the co-surfactant was added to the homogenized mixture. All the components were mixed gently using a vortex shaker at 37 0 C to get a clear homogenized mixture. The prepared liquid SNEDDS were stored tightly in the container at room temperature and were kept for further studies and formulations were recorded for any changes in turbidity or phase separation. The results obtained from responses were fitted into a 2FI model and quadratic polynomial model explained by a non-linear equation [11,19]. y=β 0 +β 1 X 1 +β 2 X 2 +β 3 X 3 +β 4 X 1 X 2 +β 5 X 2 X 3 +β 6 X 1 X 3 (1) y=β 0 +β 1 X 1 +β 2 X 2 +β 3 X 3 +β 4 X 1 X 2 +β 5 X 2 X 3 +β 6 X 1 X 3 +β Where y is the measured response β 0 -β 9 are coefficients of regression, X 1, X 2, and X 3 are independent factors. Analysis of variance (ANOVA), lack of fit, and multiple correlation coefficients (R 2 ) tests validate the models.

Preparation of 18-β Glycerrhetinic acid SNEDDS
18-β glycerrhetinic acid SNEDDS formulations were prepared by adding 50 mg of 18-β glycerrhetinic acid to the geranium oil after dissolving of the drug completely in oil added required quantity of tween 80 and DMSO to form a homogeneous mixture. The final mixtures were vortexes for 5 minutes until transparent preparations were obtained. The prepared liquid SNEDDS were placed in a tight container until used and we examined formulations for any change in turbidity or phase separation [19].

Droplet Size and Zeta Potential
The average droplet size, zeta potential, and polydispersity index of 13 formulations were determined using Malvern Zetasizer (Malvern Instruments, UK). Liquid SNEDDS were diluted 1000 times with distilled water and agitated gently to ensure proper distribution of fine emulsion in aqueous media. [11].

Dispersibility Studies
By dispersibility studies, self-emulsification time was determined. 1 ml of SNEDDS formulation was added drop-wise to 250 ml of Phosphate buffer having pH 6.8 with gentle agitation using USP Type II (paddle) dissolution apparatus having speed of 50 rpm at temperature 37 0 C ± 0.5 0 C. All the 13 formulations are visually observed and monitored for the formation of nanoemulsions and the time which was taken to disperse SNEDDS in buffer solution was recorded [20].

Percent Transmittance
% Transmittance of 18-β glycerrhetinic acid SNEDDS was determined by adding 1 ml of each formulation to 100 ml of distilled water with continuous stirring and the diluted formulation was assessed by using UV-Visible spectrophotometer (UV-1800, Shimadzu Corporation, Tokyo, Japan) at wavelength 267nm. % transmittance can be calculated by using the formula %T = I/I 0 X 100 I = amount of light that passes through the sample, I 0 = amount of light entering the sample [21].

Drug Entrapment Efficiency
The entrapment efficiency of drug 18-β glycerrhetinic acid in SNEDDS was calculated by the process of separation of SNEDDS and supernatant with centrifugation at 4000 rpm for 15 minutes. The 6 ml supernatant was further diluted with methanol and phosphate buffer pH 6.8 in ratio 2:1 after the amount of free drug was calculated by assessing it in UV Visible spectrophotometer (UV-1800, Shimadzu Corporation, Tokyo, Japan) at wavelength 267nm [22]. The formula to calculate the entrapped efficiency is

In vitro Drug Release Studies
Drug release studies of 18-β glycerrhetinic acid SNEDDS for all 13 SNEDDS formulations were done by USP dissolution apparatus II (Paddle type) in 500 ml of phosphate buffer having pH 6.8 as dissolution medium at a speed of 50 rpm and temperature 37 0 C ± 0.5 0 C. 40 mg (4 ml) of 18-β glycerrhetinic acid SNEDDS was placed in dialysis cellulose membrane bag. Aliquots of 5ml at a predetermined time interval was withdrawn (30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, and 360 min.) collected, and analyzed for 18-β glycerrhetinic acid by double-beam U.V Visible spectrophotometer at wavelength 267 nm. To keep the sink condition 5 ml, immediately fresh dissolution medium was added to the apparatus and the drug release profile from 18-β glycerrhetinic acid SNEDDS was observed [23,14].

EVALUATION OF OPTIMIZED FORMULATION
To study the effect of the composition of fresh formulation on response variables were selected and assessed for parameters or response variables such as globule size, self-emulsification time, zeta potential, PDI, % transmittance, drug release studies.

Optimising Diffusion Rates of Drug
Penetrant Polarity Gap= PPG= |log P penetrantlog P stratum corneum| PPG= |2.75-0.8|= 1.95 The log P of the vehicle chosen for 18-β glycerrhetinic acid should be 2.75+1.95 = 4.7 or higher or 2.75-1.95= 0.8 or lower. From the literature review we find, Log P value of tween 80 is 2.39, which differs from the polarity of the stratum corneum so, If the drug's polarity differs from the polarity of stratum corneum lipids, its skin penetration can be enhanced by the addition of a co-solvent that dissolves the drug and which also has a high affinity for stratum corneum lipids. So, DMSO was used as a co-solvent, having Log P -0.6, which helps in enhancing the permeation of the drug [14].

UV Characterization
UV characterization has been done for the preparation of the standard curve by making the dilutions and getting absorbance at wavelength 267 nm. The standard curve is shown in Fig. 1

Partition Coefficient
The value of partition coefficient of 18-β glycerrhetinic acid in n-octanol/phosphate buffer (pH 6.8) system was found to be 2.75 shown in Table 3. The log P value of 18-β glycerrhetinic acid indicates the drug has lipophilic nature and is having good properties for the formulation of SNEDDS.

Fourier Transform Infrared Spectrophotometer
From the FTIR studies, no interaction was found between drugs and excipients. The FT-IR spectra of the drug showed peaks at 3437. 15  There was no significant difference found in the wavenumber (cm− 1 ) of the drug, broadening effect was observed in Fig. 2.

Solubility Studies
The solubility of 18-β glycerrhetinic acid was assessed in different vehicles are shown in Fig.  3. The excipients used in the formulation of SNEDDS should solubilise the maximum quantity of drug and possess a major self-emulsification region in the ternary phase diagram and the excipients were chosen by considering the solubility and compatibility with the drug. Different solubility of the drug in different oils/surfactants/ cosurfactant is shown in Table 4.  The components that were used for the formulation of SNEDDS solubilize the maximum amount of drug and also possess a large efficient self-emulsification region in the pseudo-ternary phase diagram. We selected vehicles that are suitable for a drug on solubilizing capacity, compatibility, and safety. Among the oil tested geranium oil shows the highest solubility of the drug that was 37.5± 0.66 mg/ml, so we chose it as an oil base. Tween 80 shows high solubility that was 19.1±0.51 mg/ml among the various surfactants and screening of different cosurfactants, DMSO was selected, which shows high solubility of 38.0±1.25 mg/ml. These studies were aimed at identifying a suitable oil, surfactant, and co-surfactant.

Construction of Pseudo-ternary Phase Diagrams
Based on preformulation studies of solubility of a drug in various vehicles, pseudoternary phase diagrams were constructed by taking geranium oil as the oil phase, tween 80 as a surfactant, and DMSO as co-surfactant. The darker region shown in Fig. 4 expresses and represents the effectiveness of the self nano emulsifying region that has visual characteristics like clarity, no phase separation, and spontaneous formation of the emulsion was observed in the formulation. So it was necessary to define the range of selfemulsification regions for oil, surfactant, and cosurfactant in Box Behnken design. The % range that was selected from the pseudoternary diagram for the formation of emulsion for the independent variables were at around 16-60% for the oil 10-90% for the surfactant, and 05-40% w/w for the co-surfactant. Pseudoternary phase diagram optimizes the three components of emulsion also it is used for screening of self dispersible formulation and to find the self emulsification region. shows aggregation in the particles. If the value of PDI is more, it shows about the polydisperse system, and if the value is less, i.e. near to zero shows about the monodisperse system. The polydisperse system has a greater tendency to aggregate compared to the monodisperse system. Fig. 5 shows the prepared formulation by employing Box-Behnken design.

Box-Behnken Design Analysis
All data was obtained from design experiment 13, it auto-select the fitted model type, Responses (Y1), and (Y2) were fitted to the 2F1 model, while (Y3) was fitted to the Quadratic model. ANOVA verified the significance of the Model, Lack of fit, and multiple correlation coefficients (R 2 ) test. Table 3   0.05, which shows the value is significant, but here p-value (Y1) is greater than 0.05 which shows the value of the model is not significant. So, the p-value of (Y1) is not fitted to the quadratic model and the p-value of (Y2) is fitted to the quadratic model. The variation of data is analyzed by the Lack of fit test which is also a good statistical parameter for checking the better fitness of the model. The analyzed value should be insignificant, that is p-value should be greater than 0.05, which is relative to the pure error. R2 value that is multiple correlation coefficient tests is denoting the amount of variation around the mean and its value should be near to 1.

Particle Size and Zeta Potential
Particle size or droplet size, zeta potential, and polydispersity index (PDI) of all 13 formulations loaded with drugs were determined by Malvern Zetasizer Version 7.12 (Malvern Instruments Limited, Worcestershire, UK). 1 ml of sample from each formulation was diluted with 100 ml distilled water and agitated for proper distribution of the formulation in aqueous media. The measurements were taken in triplicate. Zeta potential is an important parameter for the characterization of the total surface charge and stability of the formulated SNEDDS.
The size of the globule of glycerrhetinic acid SNEDDS was in the range 50.24 nm to 144.6 nm as depicted in The coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant and the intercept in an orthogonal design is the overall average response of all the runs. The coefficients are adjustments around the average based on the factor settings. When the factors are orthogonal, the VIFs are 1; VIFs greater than 1 show colinearity, the higher the VIFs, the more severe the co-relation of factors. As a rough rule, VIFs less than 10 are tolerable.

Response surface and contour plot analysis
Three-dimensional response surface plots and two-dimensional contour plots of the responses across the selected factors were constructed to further explain the relationship between the independent and dependent variables [25], as shown in Figs. 6 and 7. These types of plots are very useful for studying the interaction effects between two factors and for understanding how the effect of one factor will be influenced by the change in the level of another factor. As these types of plots can only express two independent variables at a time against the response, one independent variable must always be fixed [26]. Considering the p-value of coefficients for each independent factor of the different responses [27] in Table 12, we concluded that geranium oil, tween 80, and DMSO showed the least significant contribution to responses Y1, Y2, and Y3, respectively. Therefore, these factors were fixed as mid-values when plotting the response surfaces and contour plots. The influence considering for formulation composition factors on droplet size to be one of the most crucial factors for assessing the quality of SNEDDS. It determines the rate and extent of drug release, as well as absorption. Predicted versus actual graph of globule size, self emulsification time, and percent drug release was shown in Fig. 8. Based on optimization through Box-Behnken design, a new optimized formulation having a concentration of 4.5ml, 3ml and 1 ml of oil, surfactant, and co-surfactant respectively was prepared which have an average globule size 93.42±54.17 nm found near to mean globule size 90.57 nm that was confirmed by optimal design as shown in Table 13 having PDI 0.401 however, dual peaks in the graph and value of PDI towards 1, shows the system was heterogeneous but is selected for further studies due to having desired mean droplet size as well as good zeta potential that is -28.62 mV±3.65 shown in Fig. 9. Normally, the zeta potential value ±30mV is sufficient for stability of emulsion. The results are shown below [28], so by implying this design higher-order responses surface were generated using fewer required runs than a normal factorial technique. Table 13 describe the confirmation  table after optimization.

Self
Emulsification Time of Optimized Formulation Self-emulsification time could determine the rate of emulsification which is an important index for the assessment of the efficacy of emulsification. The SNEDDS should disperse completely after when subjected to aqueous dilution under mild agitation. Table 8

Entrapment Efficiency
The encapsulation efficiency of 18-β glycerrhetinic acid in SNEDDS was found to be 80.12±1.52%. By this, easily estimate the difference between the initial drug quantity and the free or un-entrapped quantity of drug in the supernatant concerning the total quantity incorporated in the SNEDDS preparation, so in 10 ml of SNEDDS preparation, 4 ml of SNEDDS having 40 mg of drug and 6 ml of supernatant have 10 mg of an unentrapped drug, so the entrapment efficiency of 18-β glycerrhetinic acid in SNEDDS was found to be 80.12±1.52% [22].

Drug Release Studies
Dialysis cellulose membrane bag used for the drug release studies in USP dissolution apparatus II. 4 ml of drug-loaded SNEDDS equivalent to 40 mg was filled in a dialysis bag. Percent drug release in phosphate buffer (pH 6.8) was observed at different time intervals. The results of the study of cumulative % drug release studies through dialysis bags are shown in Fig.  10. The formulations were observed and found that F2, F3, F9, F11 and F13 show over 90% cumulative percent drug release in 30 min. The same process also analyzed an optimized formulation and had 91.8% cumulative percent drug release [30]. Fig. 10 showing the drug release studies of optimized formulation FF up to 360min.

Release Kinetics
Release kinetics of optimized formulation through dialysis bag is calculated by using KinetDS3.0 in table 14. AIC value tells about that our formulations fit which model, they consider low AIC value to be best, AIC value is 120.86 which is very low so it tells our formulation fits Korsmeyer Peppas model having R 2 value= 0.9862. Korsmeyer Peppas model was best employed in this formulation, to better characterize the drug release behavior.

Mt/M∞= Kt n
Where Mt/M∞ is the fractional drug release in time t, K is constant for geometric and structural characteristics of controlled-release device and n is a parameter indicating the mechanism of drug release, a plot of log % drug released vs log time yields slope n, where 0.5 value of n indicate fickian diffusion, 0.5-1 or 0.45-0.89 indicates anomalous non-fickian diffusion, 0.89-1 indicates zero-order release. Here the value of n is 0.620 indicates anomalous non-fickian diffusion.
FF formulation having n-value (diffusion exponent) 0.733, which indicates anomalous non-fickian diffusion, n-value also indicates that the geometry of swellable controlled release system is spherical [31].

Percentage Transmittance
Percentage transmittance of SNEDDS having 18-β glycerrhetinic acid was measured by taking 1 ml of formulation into 100 ml of distilled water with stirring and then this formulation was analyzed by UV-Visible Spectrophotometer at 267 nm. This study was conducted in triplicate. It found the transparency of the material and also measures the amount of light that passes through a material and is usually reported as a percent comparing the light energy transmitted through a material to the light energy that entered the material. Value of transmittance near to 100% shows the formulation was transparent as shown in Table 15 [32].

Viscosity of Formulations
The viscosity studies tell about the SNEDDS system is physically stable.
The estimated viscosity was 0.8872 cp as determined during the process of particle size analysis, and the pH was 6.8 as estimated by pH meter for all the formulations. The viscosity investigations are required for SNEDDS to physically define the system and control its stability. The viscosity of SNEDDS is crucial for their aqueous phase dispersion. Higher viscosities slow down emulsification, which might influence medication release and bioavailability profiles in vivo. The viscosity of SNEDDS formulas increased as the concentration of oil and surfactant mixture increased, according to the results of the viscosity determination. The average viscosity of the SNEDDS after 100 times dilution with pure water, the viscosity range shrank to 0.8872 cp. All of the formulas had low viscosities, indicating that the resulting nano emulsion was of the O/W type. The SNEDDS formulas in this work recorded viscosity values that were low enough to rule out the likelihood of rapid selfemulsification [33].

CONCLUSION
In this study, it was found that Box-Behnken experimental design optimised the formulation in fewer runs, the prepared formulation showing results in particle size, self emulsification time, and drug release studies which were almost near to the confirmation value were optimized by the design of experiment (DOE) software. In this study, the formulation of SNEDDS of 18-β glycerrhetinic acid (FF) was done to show good dissolution profile against pure suspension of 18β glycerrhetinic acid which employs SNEDDS have capability to enhance solubility of poorly water soluble drug which may helps further to achieve desired bioavailability through stratum corneum. Percentage transmittance shows the formulation features, including uniformity and size of the droplets.

DISCLAIMER
The products used for this research are commonly and predominantly used products in our area of research and country. There is no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by the personal efforts of the authors.

CONSENT
It is not applicable.

ETHICAL APPROVAL
It is not applicable.