Therapeutic potential of limonene-based syringic acid nanoemulsion: Enhanced ex-vivo cutaneous deposition and clinical anti-psoriatic efficacy.

Nanoemulsions have carved their position in topical delivery owing to their peculiar features of forming a uniform film on the skin and conquering stratum corneum barrier and hence fostering dermal penetration and retention. The present work developed syringic acid nanoemulsion (SA-NE) by spontaneous emulsification as an anti-psoriatic remedy via the dermal route. SA-NE were prepared with either lauroglycol90, limonene or their combination (oil phase) and tween80 (surfactant) with variable concentrations. The physicochemical characteristics of SA-NE were assessed together with Ex-vivo skin deposition and dermal toxicity. The effectiveness of optimal formula in psoriatic animal model and psoriatic patients was investigated using PASI scoring and dermoscope examination. Results showed that, SA-NE containing mixture of lauroglycol 90, limonene and 10 % tween80 (F5), was selected as the optimal formula presenting stable nanoemulsion for 2-month period, showing droplet size of 177.6 ± 13.23 nm, polydispersity index of 0.16 ± 0.06, zeta potential of -21.23 ± 0.41 mV. High SA% in different skin strata and no dermal irritation was noticed with limonene-based SA-NE also it showed high in-vitro anti- inflammatory potential compared to the blank and control formulations. A preclinical study demonstrated that limonene-based SA-NE is effective in alleviating psoriasis-like skin lesions against imiquimod-induced psoriasis in rats. Clinically, promising anti-psoriatic potential was asserted as all patients receiving F5 experienced better clinical improvement and response to therapy, achieving ≥ 50 % reduction in PASI scores versus only 35 % responders in the Dermovate® cream group. Collectively, the practical feasibility of limonene-based SA-NE topical delivery can boost curative functionality in the treatment of psoriatic lesions.