QUANTIFICATION DETECTION OF NEPETALACTONES 157 Copyright © 2007 John Wiley & Sons, Ltd. Phytochem. Anal. 18: 157–160 (2007) DOI: 10.1002.pca Phytochemical Analysis Phytochem. Anal. 18: 157–160 (2007) Published online 29 January 2007 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/pca.965 Quantification of Nepetalactones in Catnip (Nepeta cataria L.) by HPLC Coupled with Ultraviolet and Mass Spectrometric Detection MINGFU WANG, 1 * KA-WING CHENG, 1 QINGLI WU 2 and JAMES E. SIMON 2 1 Department of Botany, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China 2 New Use Agriculture and Natural Plant Products Program, Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901, USA Received 4 November 2005; Revised 12 April 2006; Accepted 13 April 2006 Abstract: Nepetalactones, the major chemical components of catnip (Nepeta cataria L.), were analysed by reversed-phase HPLC coupled with UV and MS detection. Two major nepetalactones, Z,E-nepetalactone and E,Z-nepetalactone, were successfully identi- fied and quantified. The linearity range for Z,E-nepetalactone was determined as 0.00655–0.655 mg/mL with a correlation coeffi- cient of 0.9999, and the linearity range of E,Z-nepetalactone was found to be 0.00228–0.456 mg/mL with a correlation coefficient of 0.9999, under UV detection at 228 nm. The linearity ranges were from 0.00164 to 0.0328 mg/mL, with a correlation coefficient of 0.9999, for Z,E-nepetalactone and 0.00114–0.0228 mg/mL, with a correlation coefficient of 0.9999, for E,Z-nepetalactone by MS detection with selected ion monitoring of ion peak m/z 167. The MS detection was found to be more sensitive than UV detection and this method was validated as simple, reliable and sensitive for catnip nepetalactone analysis. This method can be used for identification and fingerprinting of catnip products. Copyright © 2007 John Wiley & Sons, Ltd. Keywords: HPLC-UV; HPLC-MS; nepetalactones; catnip; Nepeta cataria L. Phytochemical Analysis * Correspondence to: Mingfu Wang, Department of Botany, The Univer- sity of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China. E-mail: mfwang@hkusua.hku.hk INTRODUCTION Catnip (Nepeta cataria L.) and related Nepeta spp., collectively referred to as catmints, have been used for ornamental and culinary purposes and as folk medi- cines with mildly sedative and antispasmodic effects for a long time (Ganzera et al., 2001). Catnip is a member of the Lamiaceae family and has a reputa- tion of stimulating and attracting cats. More recently, catnip has become of interest for its insect repellent activities. The steam distillate of catnip was found to be as good, and in some cases better, at repelling house flies, Musca domestica L., and American cockroaches, Periplaneta americana L., than widely used commercial products such as N,N-diethyl-m-toluamide or citronellal (Schultz et al., 2004). Among the chemicals identified in catnip, nepetalac- tones are of great interest owing to their potential application as aphid sex pheromones and insect repellents (Birkett and Pickett, 2003; Schultz et al., 2004). Two major nepetalactones, Z,E-nepetalactone and E,Z-nepetalactone, are found in the essential oil of catnip. Previous studies have demonstrated the E,Z- nepetalactone isomer to possess a stronger repellent activity against cockroaches than the dominant isomer, Z,E-nepetalactone, whilst both nepetalactones exhib- ited mosquito repellent activity (Coats et al., 2003; Schultz et al., 2004). In addition, the nepetalactones are characteristic for species of Nepeta and can be used as marker compounds for identification purposes and botanical standardisation applications (Ganzera et al., 2001). For this reason it is important to develop analytical methods by which to analyse the nepetalactones. As for most volatile compounds, nepetalactones are generally analysed by GC and GC-MS (Handjieva et al., 1996; Tropnikova et al., 1999; Baranauskiene et al., 2003; Morteza-Semnani and Saeedi, 2004; Schultz et al., 2004), but GC analytical procedures are some- what time-consuming. Moreover, GC analysis requires extensive preparation time involving extraction of the oil by the hydro and/or steam distillation of a large amount of plant material, and subsequent dissolution of the essential oil in organic solvent prior to analysis. HPLC offers a suitable alternative for the analysis of nepetalactones as the compounds are UV-detectable, and HPLC has been shown to be a reliable method for the analysis of the dominant isomer, Z,E- nepetalactone, in catnip oil (Ganzera et al., 2001). However, this published HPLC method was used for the determination of just one nepetalactone, and the sample preparation procedure described is complex and time-intensive, involving three extractions, an evaporation and a final dissolution of the residue in solvent. The aim of the present study was to develop and vali- date simple, fast and reliable HPLC-UV and HPLC-MS methods for the routine measurement of the major