In Vivo/In Vitro Irritation Potential of Propylene Glycol Herbal Extracts for Topical Application: Using Alchemilla vulgaris as an Example

Objective Different extraction vehicles are traditionaly used for herbal extraction. Despite its frequent use in modern cosmetic and pharmaceutical formulations, there is a lack of scientific data to support safety of propilene glycol (PG) plant extract for topical use. Methods To estimate skin safety profile of PG as extraction solvent in herbal extracts for topical use regarding the skin irritation potential, using Alchemilla vulgaris PG extract as an example. In vitro cytotoxicity alongside in vivo effects on human skin employing biophysical measurements (TEWL, erythema index and pH) were assessed. Results In vivo/in vitro testing showed a satisfactory safety profile of both PG per se and tested PG extract. Conclusion PG was shown to be a suitable solvent for obtaining bioactive plant extracts without causing serious skin irritation and suitable for topical formulations correspondent to the therapeutic need.