Effects of lead phytochemicals of Radix scutellariae on Acanthamoeba

PURPOSE. Acanthamoeba keratitis (AK), which is associated with noncompliant use of contact lenses, remains difficult to treat due to delayed diagnosis and paucity of therapeutic agents. Although improvements in activity against Acanthamoeba infection have been achieved in disinfecting solutions for soft contact lenses, such modifications have not been extended to those for special rigid gas permeable (RGP) contact lenses, which are increasingly used for myopia control in children. Phytochemicals present in herbs used for traditional Chinese medicine may be effective as therapeutic or preventive agents. The purpose of this study was to investigate amoebicidal properties of lead phytochemicals of Radix scutellariae alone and in combination with multipurpose (disinfecting) solutions (MPS) for RGP lenses. METHODS. Viability of Acanthamoeba castellani and A. polyphaga trophozoites was determined following exposure to four phytochemicals: baicalin, baicalein, wogonoside, and oroxylin A and both alone and in combination with four RGP MPS, using a modified standalone technique. RESULTS. As individual agents, wogonoside and oroxylin A showed highest activity against A. castellani and A. polyphaga trophozoites, respectively. For both organisms, the combination of baicalein and oroxylin A was superior. Effectiveness of MPS alone did not exceed 0.27 log reduction, but addition of combined baicalein and oroxylin A resulted in 0.92 and 0.64 log reductions of A. castellani and A. polyphaga, respectively. CONCLUSIONS. The combination of baicalein and oroxylin A enhanced the activity of MPS for RGP contact lenses against trophozoites of two pathogens, A. castellani, and A. polyphaga, and offers a potential therapeutic and/or preventative agent for AK.