Headspace solid-phase microextraction combined with mass spectrometry as a powerful analytical tool for profiling the terpenoid metabolomic pattern of hop-essential oil derived from Saaz variety Hop (Humulus lupulus L., Cannabaceae family) is prized for its essential oil contents, used in beer production and, more recently, in biological and pharmacological applications. In this work, a method involving headspace solid-phase microextraction and gas chromatographymass spectrometry was developed and optimized to establish the terpenoid (monoterpenes and sesquiterpenes) metabolomic pattern of hop-essential oil derived from Saaz variety as a mean to explore this matrix as a powerful biological source for newer, more selective, biodegradable and naturally produced antimicrobial and antioxidant compounds. Different parameters affecting terpenoid metabolites extraction by headspace solid-phase microextraction were considered and optimized: type of fiber coatings, extraction temperature, extraction time, ionic strength, and sample agitation. In the optimized method, analytes were extracted for 30 min at 40ЊC in the sample headspace with a 50/30 m divinylbenzene/carboxen/polydimethylsiloxane coating fiber. The methodology allowed the identification of a total of 27 terpenoid metabolites, representing 92.5% of the total Saaz hop-essential oil volatile terpenoid composition. The headspace composition was dominated by monoterpenes (56.1%, 13 compounds), sesquiterpenes (34.9%, 10), oxygenated monoterpenes (1.41%, 3), and hemiterpenes (0.04%, 1) some of which can probably contribute to the hop of Saaz variety aroma. Mass spectrometry analysis revealed that the main metabolites are the monoterpene -myrcene (53.0 ± 1.1% of the total volatile fraction), and the cyclic sesquiterpenes, ␣-humulene (16.6 ± 0.8%), and -caryophyllene (14.7 ± 0.4%), which together represent about 80% of the total volatile fraction from the hop-essential oil. These findings suggest that this matrix can be explored as a powerful biosource of terpenoid metabolites.
Keywords: Essential oil / GC-qMS / HopSaaz variety / HS-SPME / Terpenoid metabolites DOI 10.1002/jssc.201200244
IntroductionIt is well known that plant-derived natural products are extensively used as biologically active compounds. From these, the essential oils, which represent a small fraction of a plant's composition, and some of their constituents are used not only in pharmaceutical products for their therapeutic activities but also in agriculture, as food preservers and additives for human or animal use, in cosmetics and perfumes, and other industrial fields [1,2]. Particular emphasis has been Correspondence: Professor José S. Câmara, Centro de Ciências Exactas e da Engenharia, Universidade da Madeira, Campus Universitário da Penteada, 9000-390 Funchal, Portugal E-mail: jsc@uma.pt Fax: +351-291705149Abbreviations: HS-SPME, headspace solid phase microextraction; RI, retention index placed on their antibacterial, antifungal, and insecticidal activities [3]. In many cases, they serve as (i)...
