Volatiles in propolis and geopropolis from Brazilian stingless bees: a critical review

Native stingless bees play a fundamental role in the pollination of 90% of Brazil’s native flora, supporting the reproduction of wild plants, which in turn provide food and habitat for several other species. In Brazil, there are more than 200 species of stingless bees, with around 89 endemic species. Stingless bees also produce propolis, but the genus Melipona is a producer of geopropolis, a mixture of plant resins and soil. The chemical composition of volatile compounds in propolis/geopropolis, including essential oils obtained by hydrodistillation or other extractive methods, is crucial to understanding the relationship with local flora and beekeeping production. This review reports studies of the volatiles present in propolis and geopropolis of Brazilian stingless bees, the extraction and analytical methods applied, the reported chemical composition, suggested botanical origins, and possible biological activities. Surprisingly few studies were dedicated to this subject with varied extraction and analytical methods, which hinders comparison between results. Some proposals of botanical origins of the resins were reported, and only antimicrobial activity was evaluated. Due to their ecological importance and therapeutic potential, it is important to explore a greater number of stingless bee species, clearly describing the methodologies and species studied.