Chemical composition and odor intensity of plant volatile organic compounds drive medicinal use

Sensory cues like taste and smell are assumed to influence medicinal plant selection. However, the precise role of odor intensity and chemical properties awaits experimental investigation. This study investigated the correlation between Volatile Organic Compounds (VOCs) and medicinal plant selection by a local community in NE-Brazil. We conducted semi-structured interviews to identify the main plant species used within the local medical system, as well as the participants' subjective perception about the odor intensity of medicinal plants. Subsequently, we collected VOCs samples from 39 ethnospecies using dynamic headspace methods and analyzed them through gas chromatography coupled to mass spectrometry. We then tested how odor perception influences the type and number of body systems a plant treats, and how VOC emission and composition affect plant odor perception and use. Among these frequently cited, odorous medicinal plants, olfactory perception was significantly associated with a plant's citation frequency for therapeutic uses, irrespective of the associated body system. Odor intensity correlates with total VOC emission and chemical diversity, with monoterpenes specifically enhancing perceived fragrance. Furthermore, plants sharing similar VOC compositions or chemical classes often treat related body systems. These findings reveal a sensory-chemical logic in local medical systems, pointing to a critical importance of odor perception and chemical composition in the selection and use of medicinal plants, and advocating for expanded interdisciplinary research in this field.