In vitro antifungal activity and preliminary physicochemical stability of a shampoo containing a hexane extract from Agave sisalana residues

Agave sisalana processing generates large amounts of leaf residue that may represent a source of biologically active compounds. This study evaluated the in vitro antifungal activity of a hexane extract obtained from A. sisalana residue (HES) and the preliminary physicochemical stability of an HES-containing shampoo. The minimum inhibitory concentrations (MICs) of HES and ketoconazole were determined against Malassezia pachydermatis ATCC 14,522 and Trichophyton rubrum ATCC 28,189. The antifungal activity of the HES-containing shampoo against T. rubrum was subsequently evaluated by viable-count assays after 30, 60, and 90 min of contact. The formulation was also monitored for appearance, odor, homogeneity, pH, and viscosity during a 30-day stability study. HES showed MICs of 125 µg mL⁻¹ against M. pachydermatis and 750 µg mL⁻¹ against T. rubrum , whereas the corresponding MICs of ketoconazole were 112.5 and 900 µg mL⁻¹, respectively. Across the evaluated contact times, the HES-containing shampoo produced significantly lower colony-forming unit counts than the shampoo base ( p < 0.001). No statistically significant difference was detected between the HES-containing and ketoconazole-containing shampoos ( p = 0.564); however, this finding was not interpreted as evidence of statistical equivalence. No changes in appearance, odor, or homogeneity were observed throughout the 30-day evaluation. The pH remained approximately 6.0 under the evaluated storage conditions, while viscosity remained approximately 3000 cP at 25 °C. These findings support the in vitro antifungal activity of HES and warrant further investigation of the formulation, including chemical characterization of the extract, safety assessment, and longer-term stability studies.