## 3 Results and Discussion  
The solubility of MTC in the terpene, propylene glycol, and Tween 80 mixture are determined. The solubility data indicated that while nerolidol had significantly highest MTC solubility capacity (977.58 \(\pm\) 2.09 mg/mL) than those of other terpen examined (\(p<0.05\)), terpinolene had the lowest solubility capacity (826.38 \(\pm\) 1.65 mg/mL). The solubility of MTC in eucalyptol and _dl_-limonene was \(927.42\pm 0.53\) mg/mL and \(872.12\pm 0.71\) mg/mL, respectively. In this study, firstly the difference in the mechanical characteristics of the sodium alginate based MTC gels was investigated firstly using TPA. Our results are given in Table 2 and Figure 3.  
The hardness parameter represents the strength of the gel structure under compression and introduces the required force to provide the deformation of a gel formulation [30]. In the present study it is found that the hardness values of MTC gels were between 0.02 \(\pm\) 0.01 and 0.01 \(\pm\) 0.02. The hardness value of the gel formulation G-LM was the lowest at body temperature. A low hardness value has been reported as an advantage for administration to the skin or mucosa easily [35]. The hardness influences the pourability and spreadability of the gel into film molds [30]. The gel formulations G-NR, G-EU, G-TP, and G-LM in our study flowed properly and spread homogenously when poured into the film molds indicating that the obtained hardness values were appropriate. Elasticity is defined as the direction of reconstruction of the gel after its deformation by compression in a defined period of time. It significantly affects the elasticity and homogeneity of the films to be prepared by using these gels. The increase in the quantitative value of elasticity showed the decrease in the elasticity of the gel formulation [30, 36]. We observed that eucalypt containing gel formulation G-EU showed the highest elasticity value (0.87 \(\pm\) 0.05). [PERSON] _et al._, showed that sodium alginate as polymer at concentration of 4.5% and propylene glycol at a concentration of 7.5% as plasticizer were \begin{table}
\begin{tabular}{c c c c c c} \hline
**Code** & **Hardness (n)** & **Elasticity (mJ)** & **Cohesiveness** & **Adhesiveness (μ)** & **Compressibility (n\(\cdot\)mm)** \\ \hline G-NR & 0.02 \(\pm\) 0.01 & 0.71 \(\pm\) 0.04 & 0.91 \(\pm\) 0.04 & 104.33 \(\pm\) 9.02 & 0.13 \(\pm\) 0.03 \\ G-EU & 0.02 \(\pm\) 0.01 & 0.87 \(\pm\) 0.05 & 0.88 \(\pm\) 0.03 & 57.33 \(\pm\) 10.70 & 0.17 \(\pm\) 0.02 \\ G-TP & 0.02 \(\pm\) 0.01 & 0.80 \(\pm\) 0.06 & 0.85 \(\pm\) 0.12 & 85.33 \(\pm\) 4.04 & 0.17 \(\pm\) 0.05 \\ G-LM & 0.01 \(\pm\) 0.02 & 0.79 \(\pm\) 0.08 & 0.91 \(\pm\) 0.04 & 84.67 \(\pm\) 3.79 & 0.14 \(\pm\) 0.02 \\ \hline \end{tabular}
\end{table} 
Table 2: The mechanical properties of gel formulations (G-NR, G-EU, G-TP, G-LM) used to formulate transdermal films (\(n=6\)). Figure 3: The force-time plots of sodium alginate based gel formulations G-NR, G-EU, G-TP, and G-LM. suitable for fabrication of transdermal films of nifedipine [5]. Our results are in accordance with this finding. Cohesiveness parameter is a measure of the degree of difficulty in breaking down the gels internal structure and significantly affects the strength and the elasticity of the film formulations. We observed that there was not a significant difference between the gel formulations G-NR, G-EU, G-TP, and G-LM in the mean of cohesiveness (\(p>0.05\)). The cohesiveness of the sodium alginate based gels in our study ranged between \(0.85\pm 0.12\) and \(0.91\pm 0.04\) which are in accordance with literature [5]. The adhesiveness is calculated from the negative force area obtained during the first immersion period and represents the work required to overcome the attractive forces between the surface of the gel and the surface of the probe [36, 37]. In our study the adhesiveness value of gel formulation G-NR (\(104.33\pm 9.02\)) was significantly higher when compared with the adhesiveness of G-EU (\(57.33\pm 10.70\)).