Engineering an eco-friendly carvacrol microemulsion with alkyl polyglycoside: unraveling the effects of surfactant and cosurfactant on phase behavior and anti-Malassezia activity

Dandruff is a prevalent scalp disorder linked to Malassezia spp. proliferation, resulting in spurred demand for gentle antifungal solutions. Carvacrol, a plant-derived essential oil component with potent antimicrobial activity, holds promise but suffers from poor solubility. The utilization of alkyl polyglycoside (APG), an eco-friendly nonionic surfactant, in conjunction with the microemulsion technology, may enhance carvacrol delivery and efficacy. This study aims to assess the effects of surfactants and short chain alcohols on carvacrol microemulsion phase behavior and antifungal activity against M. furfur. The judicious utilization of 1,3-butylene glycol (1,3-BG) as a short chain alcohol effectively expanded the single-phase region of carvacrol microemulsions. The oil-in-water microemulsions demonstrated high transparency, excellent homogeneity, and exceptional stability. Notably, when APG was used either individually or in combination as a surfactant, its antimicrobial efficacy was superior to that of Tween-80. The antifungal performance of carvacrol microemulsions was significantly influenced by the oil-to-alcohol ratio; higher ratios resulted in enhanced antifungal activity when APG and Tween-80 were combined. When incorporated as an active ingredient in scalp care formulations, carvacrol microemulsions exhibited sustained release and prolonged inhibition of M. furfur. The synergistic application of 1,3-BG, Tween-80, and APG markedly improved the inhibitory efficacy of carvacrol against M. furfur. Thus, the developed microemulsion demonstrates strong potential as a functional ingredient for anti-dandruff products, combining efficacy with environmental sustainability.