Development and Ex Vivo Assessment of Topical Formulations for Delivery of Stigmasterol and β‑Sitosterol

Phytosterols are sterol compounds naturally produced by plants and fungi, known for their ability to interact with steroid receptors and promote anti-inflammatory effects. This study aimed to investigate their potential for topical application by developing and assessing formulations containing stigmasterol (STIG) and β-sitosterol (β-SIT). A gel-cream and a topical film were prepared, and an HPLC-UV-DAD method was developed and validated for the simultaneous quantification of both phytosterols. Ex vivo skin penetration was evaluated using porcine ear skin mounted on vertical Franz diffusion cells. The analytical method demonstrated high selectivity, linearity, precision, and accuracy, with satisfactory recovery in spiked skin samples, and the penetration study showed that β-SIT incorporated into the topical film achieved significantly higher deposition in the viable epidermis and dermis compared with the gel-cream (44.16 ± 19.69 vs 17.65 ± 15.68 μg/cm²; a 2.5-fold increase). These findings highlight the potential of phytosterol-based topical systems for the development of innovative therapies targeting skin inflammation.