Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycaemic and anti-hyperlipidemic activities, among others. The biological activity of guava leaves belongs mainly to phenolic compounds. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation state (low, medium and high). The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-qTOF-MS. We identified seventy-to phenolic compounds and, to our knowledge, twelve of them were determined for the first time in guava leaves in negative ionization mode. Moreover, positive ionization mode allowed the identification of the cyanidin-glucoside. To our knowledge this compound has been identified for the first time in guava leaves.

The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation have a higher content gallic and ellagic derivatives and flavonols compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively.

The qTOF platform permitted the determination of several phenolic compounds and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production.