Determination of Monoterpene Hydrocarbons and Alcohols in Majorana hortensis Moench by Micellar Electrokinetic Capillary Chromatographic M. R. A. RODRIGUES, ² E. B. CARAMA ˜ O, ‡ L. ARCE, § A. RI ÄOS, § AND M. VALCA Ä RCEL* ,§ Institute of Chemistry and Geology, University Federal of Pelotas, Pelotas, RS, Brazil, Institute of Chemistry, University of Rio Grande do Sul, 91501970 Porto Alegre, RS, Brazil, and Analytical Chemistry Division, Campus de Rabanales, Edificio Anexo C-3, University of Co ´rdoba, E-14071 Co ´rdoba, Spain Micellar electrokinetic capillary chromatography was used to determine the essential oils obtained by steam distillation of different samples of marjoram (Majorana hortensis Moench) dried leaves and flowers. The electrophoretic method consisted of a running buffer of 10 mM NaH 2 PO 4 , 6 mM Na 2 B 4 O 7 , 50 mM SDS, 7 mM γ-cyclodextrin, and 10% acetonitrile, adjusted to pH 8.0 by the addition of 0.1 M H 3 PO 4 . The following monoterpene hydrocarbons and alcohol compounds were extracted from real samples and determined by the method proposed: R-pinene, γ-terpinene, R-terpinene, terpinolene, p-cymene, linalool, R-terpineol, and terpinen-4-ol. The most prominent component of dried leaves, flowers, and commercial samples was terpinen-4-ol in four of the samples analyzed; only in one sample was R-terpineol present as the major compound. KEYWORDS: Majorana hortensis Moench; essential oil; micellar electrokinetic capillary chromatography; monoterpene hydrocabons and alcohols INTRODUCTION The vernacular term marjoram comprises several aromatic Labiatae herbs belonging to different species. Origanum ma- jorana L. (syn. Majorana hortensis Moench., M. Vulgaris Miller) is the type of marjoram most well-known. This type of sample is a native of Cyprus and southern Turkey. It is cultivated extensively as sweet marjoram, an annual herb, in several areas of Europe, Africa, America, and Asia. The dried leaves of sweet marjoram are widely used by the food industry as flavoring agents for dressings and soups and in the formulation of vermouth and bitters, among others (1-3). The essential (volatile) oil of sweet marjoram has been known since antiquity due to its biological activities, such as antibacterial, antifungal, and antioxidant properties. For all of these reasons, the flavor composition of cultivated marjoram has been investigated in recent years (4, 5). Nyka ¨nen (6) has demonstrated that the aroma composition varies with the origin of plants and many other factors. These authors found essential oils of marjoram with high contents of monoterpene alcohols and other phenols. The term essential oil implicates by definition the method of preparation, namely, the separation of volatile substances by distillation at atmospheric pressure and elevated temperature (7). In some oils, terpinen-4-ol was the major component, alone or together with other monoterpene alcohols such as cis- and trans-sabinene hydrate and R-terpineol. High contents of car- vacrol (65%) were found in marjoram oil by Sarer et al. (3), whereas Nyka ¨nen (6) reported a type of marjoram oil with high levels of thymol (up to 47%). Other methods of distillation, such as simultaneous steam distillation-extraction (SDE) and supercritical fluid extraction (SFE), can also produce high-quality essential oils from herbaceous materials (8, 9). Capillary gas chromatography with mass spectrometry was widely used to analyze the composition of essential oils (3-12). High-performance liquid chromatog- raphy (HPLC) is widely employed for the determination of antioxidants present in extracts from plants (13, 14). Nowadays, micellar electrokinetic capillary chromatographic (MEKC) is also used for the separation and quantification of these hydrophobic antioxidants, which can be present as different enantiomeric compounds (15, 16). MEKC is a mode of capillary electrophoresis based on different partitioning of the analytes between the micelle and aqueous phase. The addition of modifiers was necessary to separate compounds that migrated at the same velocity as the micelle. For the separation of this type of analyte, cyclodextrins (R, , and γ) and organic solvents such as methanol and acetonitrile are generally employed. Determination of the chemotype in marjoram samples is very important for the industry and in some biomedical research works. Monoterpene alcohols are the main aroma components * Author to whom correspondence should be addressed (e-mail: qa1ricaa@ uco.es.). ² University Federal of Pelotas. ‡ University of Rio Grande do Sul. § University of Co ´rdoba. J. Agric. Food Chem. 2002, 50, 4215-4220 4215 10.1021/jf011667n CCC: $22.00 © 2002 American Chemical Society Published on Web 06/19/2002