Changes in phytochemical composition, bioactivity and in vitro digestibility of guayusa leaves (Ilex guayusa Loes.) in different ripening stages

BACKGROUND: Guayusa (Ilex guayusa Loes.) leaves, native of the Ecuadorian Amazon, are popularly used for preparing teas. This study aimed to assess the influence of leaf age on the phenolic compounds and carotenoids and the bioactivity and digestibility (in vitro) of aqueous and hydroalcoholic leaf extracts. RESULTS: In total, 14 phenolic compounds were identified and quantified. Chlorogenic acid and quercetin-3-O-hexose were the main representatives of the hydroxycinnamic acids and flavonols respectively. Seven carotenoids were quantified, lutein being the main compound. Ripening affected phenolic content significantly, but there was no significant difference in carotenoid content. Antioxidant capacity, measured by the DPPH^• method, was also significantly affected by leaf age. The measurement of in vitro digestibility showed a decrease in phenolic content (59%) as well as antioxidant capacity, measured by the ABTS^•+ method, in comparison with initial conditions of the guayusa infusion. Antibacterial and anti-inflammatory activities were assayed with young leaves owing to their higher phenolic contents. Guayusa did not show any antibacterial activity against Escherichia coli ATCC 25922 or Staphylococcus aureus ATCC 25923. Finally, the hydroalcoholic and aqueous extracts exhibited high in vitro anti-inflammatory activity (>65%). CONCLUSION: Young guayusa leaves have potential applications as a functional ingredient in food and pharmaceutical industries.