Guava is an evergreen shrub that is cultivated throughout the world and used in traditional medicinal systems. Guava leaves contain essential oil, tannins, flavonoids, phenol compounds, carotenoids, and vitamin C. Flavonoids are mainly rich in quercetin, saponins, alkaloids, cardiac glycosides, phlobatannins, and anthraquinones. The concentration of each of these chemical components differs depending on the type of species or cultivar as well as cultivation conditions such as soil type, weather, irrigation, pruning, and other horticultural practices. Guava fruit is used in jams, drinks, and food stuff. The leaves of guava are used to cure dysentery, gastroenteritis, diabetes mellitus, stomach ache, and injuries. Research is being done on increasing the per hectare production of guava, but still there is a need to develop some methods that can amplify the amount of essential oil in the guava so it can be used in medicine in a more effective way. © 2020 Elsevier Ltd.