This work describes the importance of using renewable sources in experimental classes for undergraduate students, as well as to spread the ideas of using biomass wastes as a source of products of interest. Therefore, in the proposed experiment, citrus fruit peel waste was employed to obtain pure flavonoids by extraction and recristalization. These procedures are important to reveal to students how bioactive products can be easily obtained from natural sources. In this way, naringin and hesperidin could be efficiently extracted from grapefruit (Citrus x. paradisi L.) and common orange (Citrus sinensis L. osbeck) peel wastes, respectively, using simple alcohols as solvents.