Agradecimentos: BN Paulino, GNS da Silva, FF Araújo, G Molina, GM Pastore and JL Bicas acknowledge the Coordination for the Improvement of Higher Education Personnel (CAPES) – Finance Code 001. F.F. Araújo acknowledge the São Paulo Research Foundation (FAPESP -Grant number 2020/15163–6). G Molina acknowledge the ‘Fundação de Amparo à Pesquisa do Estado de Minas Gerais’ (Fapemig – Grant number APQ-01056-17) and ‘Universidade Federal dos Vales do Jequitinhonha e Mucuri’ (UFVJM). GM Pastore and JL Bicas acknowledge the São Paulo Research Foundation (FAPESP - Grant numbers2016/21619–7, and 2020/06814–3) for the financial support Ver menos

Abstract: Background Monoterpenes are natural aroma compounds that can be found in plants and processed foods, being used as flavoring agents in cosmetic, pharmaceutical and food industry. Essential oils are liquid mixtures of volatile and semi-volatile compounds, mainly monoterpenes and sesquiterpenes, from plant secondary metabolism and have showed great diversity in terms of chemical composition. Several in vitro and in vivo biological properties have been reported to these compounds demonstrating that may be useful, not only as aroma compounds, but also as bioactive molecules due to different biological activities such as antimicrobial and antioxidant. In this sense, these compounds have been employed for functional and technological purposes, including in diet supplementation, as animal feed additives, bioactive food packing development, and bioinsecticides. Scope and approach In this review are highlighted the main concepts regarding monoterpenes and monoterpene-rich essential oils (MREO) as well as their biological activities and applications. A critical approach based on the analysis and discussion of the most relevant studies on these substances is used. In this sense, the influence of chemical features in the biological activities are analyzed as well as the safety and toxicological concerns are discussed. Additionally, the functional and technological applications of monoterpenes and MREO are highlighted and discussed. Key findings and conclusions The profile of biological activities is relevant to guide the use of monoterpenes and MREO for health or technological purposes. The knowledge of the physicochemical properties, through in silico drug-likeness study, and the correlation with the structural characteristics can be considered as important tools to understand the biological activities these compounds and consequently their applications. Thus, monoterpenes or MREO have been employed as additives in animal feed, in the manufacture of bioactive food packaging, as nutraceutical in diet supplementation, and as biocontrol agent for agri-food purpose demonstrating their versatility of application in food industry and related sectors Ver menos