Development of a Novel TLC Identification Test for “Rosemary Oil” and “Rosemary Water” Listed in the Japanese Standards of Quasi-Drug Ingredients

Rosemary oil (RO) and rosemary water (RW) are widely used ingredients in cosmetics. According to the Japanese Standards of Quasi-Drug Ingredients (JSQDI), RO is defined as an essential oil obtained by the steam distillation of fresh rosemary (Rosmarinus officinalis L.) leaves, branches, and flowers, whereas RW is the water layer obtained from the steam distillation of the leaves. Although the JSQDI outlines a specific TLC identification test for RW, this test is time-consuming (15-cm development distance) and requires the use of hazardous reagents (toluene). Additionally, no identification tests are available for RO. This study therefore aimed to establish a new TLC-based identification test for RO in JSQDI, while also improving the RW identification test. Using cyclohexane/methyl tert-butyl ether/acetonitrile (20 : 10 : 1) as the developing solvent and 4-methoxybenzaldehyde sulfuric acid as the visualization reagent, 1,8-cineole and borneol were universally detected in 19 RO market products. Thus, 1,8-cineole was selected as the primary marker compound and borneol as the secondary marker compound. Additionally, the extraction process was optimized by applying these TLC conditions to RW, significantly simplifying the process. TLC analysis of the RW market products confirmed the presence of 1,8-cineole in all samples. Thus, in addition to representing a novel method for the identification of RO, these results indicate the suitability of the new extraction conditions for use as an alternative method to identify RW.