Parâmetros de qualidade, eficácia e segurança das folhas de Anacardium occidentale L. da amazônia maranhense: abordagem integrada entre farmacognosia, microbiologia e ecotoxicologia

Abstract

Anacardium occidentale L., popularly known as cashew tree, is a native species from northeastern Brazil widely used for its therapeutic properties, including antioxidant, anti-inflammatory, and antimicrobial effects. The leaves of this species, which are responsible for such activities, are underutilized. Their analysis allows us to understand their composition and adaptive responses. This study aimed to validate A. occidentale L. leaves grown in the Maranhão Amazon by determining authenticity parameters and assessing the species' antimicrobial potential and safety. The samples were collected in the Itaqui-Bacanga area in São Luís, Maranhão, in September and October 2022, and identified in the Maranhão Herbarium/UFMA. The fresh leaves were subjected to morphoanatomical analyses with unaided vision and by paradermal and cross sections. After drying and spraying, the material was subjected to maceration in 70% ethanol, obtaining the crude hydroalcoholic extract of the leaves (EBF). The EBF was subsequently fractionated successively with solvents of increasing polarity, obtaining the fractions in hexane (FHX), chloroform (FCL), and ethyl acetate (FEA). Chemical analyses included phytochemical tests thin layer chromatography (TLC), and high performance liquid chromatography (HPLC). The antibacterial activity was evaluated against Staphylococcus aureus (strains ATCC 25923, ATCC 6538, and clinical) by agar diffusion and microdilution methods in 96-well plates, determining the inhibition zones, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Toxicity was evaluated by hemolysis and Tenebrio molitor larvae tests. The leaves were hypostomatic, with paracytic stomata, dorsiventral mesophyll, and rare glandular trichomes. Chemical analysis of EBF indicated the presence of flavonoids and terpenes. While the fractions FHX, FCL, and FEA showed tannins, phenols, flavonoids and saponins. EBF and FEA demonstrated significant inhibitory activity against S. aureus, with inhibition zones of 12 to 26.3 mm, respectively, at a 2 mg/mL concentration. The MICs were 2 mg/mL for EBF and 1 mg/mL for FEA. The MBC was observed only for FAC (2 mg/mL) against the S. aureus ATCC 25923 strain. The hemolytic activity was low (EC50 between 1799 and 8863 µg/mL), and the average survival rate of Tenebrio molitor larvae was 70% at the concentrations evaluated. This study contributes to the advancement of new therapeutic strategies, reinforcing guidelines for the quality, efficacy, and safety of A. occidentale leaves, furthermore evidencing their bacteriostatic and bactericidal activity, with low toxicity.