Repellent efficacy of water-balm formulation against Aedes aegypti based on zedoary, Curcuma zedoaria

Abstract

Essential oil from Curcuma zedoaria rhizomes is rich in bioactive sesquiterpenes with reported insect-repellent properties; however, its application as a topical mosquito repellent remains insufficiently explored. In this study, essential oil from C. zedoaria rhizomes was obtained by hydrodistillation and characterized using gas chromatography-mass spectrometry (GC-MS), followed by formulation into a hydroalcoholic water-balm containing 15% (w/w) essential oil. Repellent efficacy against adult female Aedes aegypti was evaluated using the Arm-in-Cage assay over a 180-min period, and cutaneous irritation was assessed in 12 adult volunteers using a standardized patch test. GC-MS analysis identified 37 compounds representing 99.98% of the total oil composition, predominantly sesquiterpenes, with AR-turmerone (23.66%), zingiberene (14.74%), and β-sesquiphellandrene (10.64%) as the major components. The formulation was well tolerated, with no skin irritation observed in any participant. Repellent activity was strong and sustained, providing 100% protection during the first 60 min post-application. Median repellency remained high at 98.50% at 120 min and 93.06% at 180 min, with an overall median repellency of 97.82%. The median complete protection time was 150 min (range: 90–180 min). These findings demonstrate that the C. zedoaria-based water-balm formulation provides effective protection against Ae. aegypti and supports the development of zedoary essential oil as a promising botanical alternative to synthetic mosquito repellents.