Recent Findings in the Chemistry of Odorants from Four Baccharis Species and Their Impact as Chemical Markers by Manuel Minteguiaga a ), Noelia UmpiØrrez a ), Vanessa Xavier b ), Aline Lucas b ), Claudio Mondin c ), Laura FariÇa d ), Eduardo Cassel b ), and Eduardo Dellacassa* a ) d ) a ) Cµtedra de Farmacognosia y Productos Naturales, Facultad de Química, Universidad de la Repfflblica (FQ-UdelaR), Av. General Flores 2124, 11800 Montevideo, Uruguay (phone: þ 598-29244068; e-mail: edellac@fq.edu.uy) b ) Laboratório de OperaÅðes Unitµrias (LOPE), Faculdade de Engenharia, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Av. Ipiranga 6681, CEP: 90619-900, Porto Alegre, RS, Brasil c ) Departamento de Biodiversidade e Ecologia, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Av. Ipiranga 6681, CEP: 90619-900, Porto Alegre, RS, Brasil d ) Laboratorio de Biotecnologia de Aromas, Facultad de Química, Universidad de la Repfflblica (FQ- UdelaR), Av. General Flores 2124, 11800 Montevideo, Uruguay Baccharis is a widespread genus belonging to the Asteraceae family that includes almost 400 species exclusively from the Americas. Even when studied in detail, the taxonomic classification among species from this genus is not yet fully defined. Within the framework of our study of the volatile composition of the Baccharis genus, four species ( B. trimera, B. milleflora, B. tridentata, and B. uncinella) were collected from the (Campos de Cima da Serra) highlands of the Brazilian state of Rio Grande do Sul. The aerial parts were dried and extracted by the simultaneous distillation extraction (SDE) procedure. This is the first time that SDE has been applied to obtain and compare the volatile-extract composition in the Baccharis genus. Characterization of the volatile extracts allowed the identification of 180 peaks with many coeluting components; these latter being detailed for the first time for this genus. The multivariate statistical analyses allowed separating the volatile extracts of the four populations of Baccharis into two separate groups. The first one included the B. milleflora, B. trimera, and B. uncinella volatile extracts. The three species showed a high degree of similarity in their volatile composition, which was characterized by the presence of high contents of sesquiterpene compounds, in particular of spathulenol. The second group comprised the extract of B. tridentata, which contained a-pinene, b-pinene, limonene, and ( E)-b- ocimene in high amounts. 1. Introduction. – Nowadays, there is an increasing interest in understanding the role of plant volatile metabolism, not only for academic reasons, but also due to the role these compounds play in the health, pharmaceutical, agricultural, food science, and flavor and fragrance industries [1] [2]. In the phytochemical nomenclature, there is a difference between biogenic volatile organic compounds (VOCs) and essential oils. The first ones represent all the compounds that plants might emit to the atmosphere [3] [4], while essential oils respond more to an operational definition that comprises a mixture of compounds that can condense when a plant is distilled [5]. In general, it ought to be seen like all plants emit volatile compounds, but not all plants can produce essential oils. Plants that produce essential oils are usually known as aromatic plants and eventually can be CHEMISTRY & BIODIVERSITY – Vol. 12 (2015) 1339 # 2015 Verlag Helvetica Chimica Acta AG, Zürich