*4.11. Ferric-Reducing Antioxidant Power (FRAP)*

In brief, 2.5 mL of 0.2 M sodium phosphate buffer (pH 6.6) and 2.5 mL of 1% (*w*/*v*) potassium ferricyanide solution were combined with 1 mL of sample solution (10 µg/mL) in methanol. Employing a method similar to Oyaizu's with a few minor alterations, the reduction power (antioxidant) of CVC in the niosomal formulation was determined. The mixture was then incubated for 20 min at 50 ◦C before being treated with 2.5 mL of 10% trichloroacetic acid. Then, 2.5 mL from the top layer of the mixture, 2.5 mL of distilled water, and 0.5 mL of FeCl<sup>3</sup> (0.1%) were added after the mixture had been centrifuged for 10 min at 3000 rpm. The amount of ascorbic acid that was utilized as the standard was 10 µg/mL, and a spectrophotometer was used to measure the absorbance at 700 nm. Each test was performed in triplicate [70].

### *4.12. Stability Studies*

Optimized CVC-N and CVC-N gel formulations underwent short-term accelerated stability evaluation in line with the International Conference on Harmonization (ICH) Q1 A R2 guidelines. Lyophilized niosomes (CVC-Ns) were placed in an Eppendorf, sealed, and maintained in a stability chamber at 25 ± 2 ◦C and RH 60 ± 5% at 4 ± 2 ◦C. The formulation along with the gel was then assessed for changes in physical appearance, shape, vesicle size, PDI, zeta potential, clarity, homogeneity, pH and phase separation for six months [71].

**Author Contributions:** Conceptualization, A.A. and M.G.; methodology, M.G. and U.H.; software, A.A.; validation, M.H.A. and U.H.; formal analysis, U.H. and M.G.; investigation, U.H. and M.G.; resources, U.H.; data curation, M.H.A.; writing—original draft preparation, M.H.A. and A.A.; writing—review and editing, M.G. and U.H.; visualization, U.H.; supervision, M.G. and A.A.; project administration, M.H.A. and M.G.; funding acquisition, M.H.A. and M.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through Small Groups Project under grant number (RGP1/399/44).

**Institutional Review Board Statement:** The animal study was duly approved by the Standing Committee of Bioethics Research (SCBR-020-2023), Prince Sattam bin Abdulaziz University Al-Kharj, Saudi Arabia.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** There is no conflict of interest.

### **References**


**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
