Since the 1950s, guavas – particularly the leaves – have been a subject for diverse research in chemical identity of their constituents, pharmacological properties and history in folk medicine. Most research, however, has been conducted on apple guava (P. guajava), with other species remaining undefined.
From preliminary medical research in laboratory models, extracts from apple guava leaves or bark are implicated in therapeutic mechanisms against cancer, bacterial infections, inflammation and pain. Essential oils from guava leaves display anti-cancer activity in vitro.
Guava leaves are used in folk medicine as a remedy for diarrhea and, as well as the bark, for their supposed antimicrobial properties and as an astringent. Guava leaves or bark are used in traditional treatments against diabetes. In Trinidad, a tea made from young leaves is used for diarrhea, dysentery and fever.