Stability, Bioactivity, and Skin Penetration of Prunus Leaf Extracts in Cream Formulations: A Clinical Study on Skin Irritation

Prunus leaf extracts are rich in phenolic and flavonoid compounds like rutin, and they are known for their antioxidant potential. This study compares the bioactivity and stability of leaf extracts from Prunus domestica L. (EL), Prunus salicina Lindl. (JL), and Prunus cerasifera Ehrh. (CL) and evaluates the dermal safety of a cream containing the extract with the most favorable in vitro properties for potential cosmetic use. Ethanolic extracts were assessed for total phenolic and condensed tannin contents, as well as antioxidants, using DPPH assay and lipid peroxidation inhibitory activities. The CL extract exhibited moderate total phenolic content, the highest condensed tannin content, and strong antioxidant (IC50 = 22.1 ± 3.1 µg/mL) and anti-lipid peroxidation (62.3 ± 1.0%) activities. Based on these results, CL was incorporated into a cream formulation (CCL), which was then evaluated for physicochemical properties, antioxidant retention, and in vitro skin permeation using Franz diffusion cells. The formulation remained physically stable under ambient conditions and retained antioxidant activity above 74.5% under thermal cycling conditions. Rutin from the CCL formulation was retained within the Strat-M™ membrane (4.0 ± 1.1%), which was 5.7-fold higher than that of the control (0.7 ± 0.6%) over 8 h; however, it was not detected in the receptor chamber under these in vitro conditions. A semi-open patch test conducted on 26 healthy volunteers under double-blind conditions revealed no signs of irritation, confirming the formulation’s dermal safety. Overall, the findings support the feasibility of using P. cerasifera extract as a stable antioxidant component in topical skincare formulations.