Prospecção química e atividade alelopática do extrato das folhas de Psidium guajava

Abstract

Psidium guajava L., commonly known as guava and belonging to the Myrtaceae family, is a widely cultivated plant valued in traditional medicine for its therapeutic properties. Its leaves are used to treat various conditions, such as cancer, hypertension, intestinal irregularities, diabetes, cough, scurvy, and weight loss. Bioactive compounds, including terpenoids, flavonoids, coumarins, and cyanogenic acids, have been identified in its leaves. This study aimed to investigate the chemical profile and allelopathic activity of the hydroalcoholic crude extract from Psidium guajava leaves. The plant material was collected in Itacoatiara, dried, ground, and extracted under reflux with 70% ethanol. Liquid-liquid partitioning using hexane, chloroform, ethyl acetate, and butanol was performed to obtain fractions of varying polarity. The allelopathic assay evaluated the effect of P. guajava extracts on the germination and growth of lettuce (Lactuca sativa) and tomato (Solanum lycopersicum) seeds. Seeds were incubated with different extract concentrations, and results were compared to a distilled water control. The observed inhibition confirmed the allelopathic activity of the tested compounds. Chemical analysis of the crude extract identified hydrolyzable tannins, flavanonols, saponins, and free steroids. The hexane and chloroform fractions showed free steroids, while ethyl acetate, butanolic, and hydroalcoholic fractions exhibited flavanonols. Phenols were detected in the ethyl acetate fraction, condensed tannins in butanolic and hydroalcoholic fractions, and saponins in both the crude extract and hydroalcoholic fraction. The allelopathic assay results revealed inhibitory effects on lettuce and tomato seeds, with stronger activity at higher extract concentrations. This study highlights the bioactive potential of Psidium guajava leaves and their relevance for both pharmacological and agricultural applications.