# Antinociceptive Effect of an Aqueous Extract and Essential Oil from _Baccharis heterophylla_
## 1 Introduction  
As in many rural regions of the world, the population of Capululapam de Mendez, a Zapotec community with well-preserved nature in the state of Oaxaca (Mexico), strongly depends on traditional herbal medicine to meet their primary health care needs [1]. This town has a Traditional Indigenous Medicine Center, which offers healing services to its inhabitants based on regional plants; this practice is firmly anchored in this community's social structure and associated with its ancestral culture and history [2]. Thus, the medicinal plants of Capulalpam de Mendez are an essential part of their lives; accordingly, it is critical to analyze them for the development of evidence-based traditional medicines with known quality, security, and efficacy.  
For instituting knowledge-based herbal traditional medicines, whose use is founded on the experience, it is necessary to determine their safety and efficacy using preclinical and clinical assays. When assessing medicinal plants' efficacy, it is crucial to analyze the traditional remedies and their constituents (e.g., flavonoids, terpenoids, phenylpropanoids, alkaloids, or others), considering that usually the efficacy is accomplished with the mixtures of compounds in these preparations. The mixture of compounds might be acting by synergistic multi-target effects, improving pharmacokinetic parameters or other mechanisms.  
For quality control of these herbals drugs is important to establish a physicochemical evaluation of crude drug covering aspects, such as selection, macro, and microscopic examination, for detection of the right material, and search of adulterants; qualitative chemical evaluation for identification of single, or a set of constituents (active or not) using chromatography or other analytical procedures; and, finally, quantitative chemical evaluation to estimate the amount of the major classes or constituents, active or not. The processes mentioned involve a wide array of scientific investigations, including physical, chemical, and biological evaluations employing different analytical methods and tools. Altogether, these studies can lead to the development of standardized phytomedicines of good quality [3; 4].  
One of the medicinal species used in Capulalpam de Mendez for painful and inflammation disorders is _Baccharis heterophylla_ Kunth (Asteraceae), a plant widely distributed in Mexico; the aerial parts of this species are consumed in the form of infusions, decocations, or poultices [5; 6; 7; 8; 9; 10]. _Baccharis heterophylla_ is known as \"chamizo de barrer\", \"curacuata\", \"jarakatua\", and \"hierba de la mula\"; among others, and it is also employed widely outside Oaxaca for treating painful complaints. Phytochemical investigations of an exudate from _B. heterophylla_ recollected in a not specified location of Oaxaca, Mexico, led to the isolation of different types of secondary metabolites, including flavonoids such as apigenin, genkwanin, and naringenin [11], two triterpenes, oleanolic acid, and maniladiol [11; 12], a few sesquiterpenoids and two dimeric clerodanes [13]. Previous pharmacological studies have shown that the CHCl\({}_{3}-\)MeOH (1:1) extract of _B. heterophylla_ produced a concentration-dependent inhibition of spontaneous ileum contractions and activated Ca\({}^{2+}\)-dependent chloride channels in _Xenopus laevis_ oocytes [6; 14]. However, the species' efficacy to treat painful complaints, chemical analysis to determine the major compounds of the traditional preparation, and to establish identity and composition tests remain open questions  
Based on the above considerations, the aims of this study were: (i) To investigate the preclinical efficacy of an aqueous extract (AE), and essential oil (EO) prepared from the aerial parts of _B. heterophylla_ for treating painful ailments, as well as their chemical composition. (ii) To develop an analytical method using High-Performance Liquid Chromatography (HPLC) to quantify the major components of the traditional preparation.