Comprehensive chemical and multivariate characterization of Amazonian guarana (Paullinia cupana) seed coats: Insights for sustainable valorization.

Guarana is a fruit native to the Amazon and is widely recognized for its stimulant properties and economic importance in Brazil, the world's leading producer. However, guarana processing utilizes only the seeds, generating substantial amounts of residues, particularly seed coats. Despite being treated as waste, these residues may constitute valuable sources of nutrients and bioactive compounds, offering opportunities for upcycling and sustainable valorization. This study comprehensively characterized guarana seed coats (PR1, PR2, and PR3) sourced from producers in Amazonas State, Brazil, through integrated physicochemical, compositional, chromatographic, and multivariate analyses. The samples evaluated exhibited high dietary fiber (61.96-64.42%) and protein contents (15.93-17.33%), alongside relevant concentrations of structural carbohydrates (total lignin: 27.59-39.98%; cellulose: 17.19-31.52%; hemicellulose: 9.45-26.27%) and essential minerals, particularly Ca, Mg, K, Cu, and Mn. The residues also showed high concentrations of bioactive compounds, mainly caffeine (16.96-28.88 mg/g) and epicatechin (0.50-12.53 mg/g). Multivariate analyses (PCA and ComDim) revealed distinct compositional profiles among the evaluated production sources, with PR1 as being associated with the highest levels of bioactive compounds, PR2 with elevated structural carbohydrate contents, and PR3 with higher concentrations of essential minerals. Overall, the findings provide a comprehensive compositional basis to support the sustainable valorization of guarana seed coats and future studies evaluating their technological functionality, safety, and food applications, contributing to circular economy strategies.