Seasonal Phenolic Profile, Antioxidant, and Photoprotective Activities of <i>Psidium guajava</i> L. Leaves

This study aimed to evaluate the phytochemicals from extracts of Psidium guajava L. leaves (P. guajava extract [PGE]) and its antioxidant and photoprotective effects. PGE showed constant production of total phenolics and maintained high antioxidant capacity across seasons and years. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis revealed the phenolic compounds quercetin, catechin, gallic acid, epicatechin, vanillic acid, and syringic acid, as well as two new compounds, syringaldehyde and ferulic acid. The high sun protection factor (SPF) was observed in all seasons. The phytochemicals ferulic acid, syringic acid, and quercetin were correlated with cloudiness and humidity. Antioxidant activity was correlated with vanillic acid, ascorbic acid, flavonoids, and tannins, and SPF with temperature, antioxidant activity, flavonoids, vanillic acid, gallic acid, and catechin. The formulations containing UVA/UVB filters or not, plus aqueous autumn extract, showed an increase in SPF. Therefore, the results suggested that PGE has potential photoprotective and antioxidant agents for the production of new sunscreen formulations with environmental and health benefits.