GREEN SOLVENT EXTRACTION OF Psidium guajava L. LEAVES: ANTIOXIDANT ACTIVITY AND ANTIBACTERIAL POTENTIAL OF THE EXTRACTS

The search for natural compounds with high antioxidant and antimicrobial potential has been increasingly explored worldwide. Studies on guava leaves (Psidium guajava L.) have already evaluated them as a potential natural preservative, but they have seen limited application in the food industry. This study aimed to evaluate the antioxidant and antimicrobial activities of guava leaf extracts obtained using ethanol and water as extraction solvents. Two extraction procedures were employed: (1) extraction with 70% (v/v) ethanol at a ratio of 1:20 (w/v) for 30 min at 25 °C, followed by filtration and solvent removal under reduced pressure using a rotary evaporator; and (2) extraction with distilled water at a ratio of 1:50 (w/v) under continuous stirring (500 rpm) at 95 °C for 10 min. The resulting extracts were filtered and freeze-dried. Analyses were performed to quantify total phenolic compounds (Folin-Ciocalteau method), total flavonoids (aluminum chloride colorimetry), in vitro antioxidant activity (DPPH, ABTS, and FRAP), and antibacterial activity by microdilution in Mueller-Hinton broth, assessing the IC₅₀ for the bacterial strains Escherichia coli and Staphylococcus aureus. The results were expressed as mean ± standard deviation, and the Shapiro-Wilk test (p < 0.05) was applied to confirm the normality and homoscedasticity of the data. The data were then analyzed using Student’s t-test for comparing means (p < 0.05), with STATISTICA® software (version 13.3). As a result, a significant difference (p < 0.05) was observed in the total phenolic compound content and antioxidant capacity, with higher values for the water extraction (TPC = 79.82 ± 3.20 mg GAE/g dry leaf; DPPH = 188.15 ± 6.52 µmol TE/g dry leaf; ABTS = 453.01 ± 11.10 µmol TE/g dry leaf; FRAP = 604.98 ± 26.42 µmol TE/g dry leaf). In contrast, ethanol extraction resulted in a significantly higher total flavonoid content (18.97 ± 0.69 mg CAT/g dry leaf), indicating a greater affinity of flavonoids for the hydroethanolic solvent. Regarding antibacterial activity, the extract prepared with 70% ethanol showed the greatest potential (IC₅₀ of 0.868 mg/mL for E. coli and 0.417 mg/mL for S. aureus), corresponding to 18.86% and 10.16%, respectively, of the antimicrobial of Cephalexin. It can be concluded that the water extract exhibited greater antioxidant activity and a higher content of phenolic compounds compared to the ethanol extract. However, the latter demonstrated greater antimicrobial efficacy, a characteristic that may make it more promising for use in foods and beverages as a natural preservative. In addition, the ethanol extract also exhibited antioxidant activity, providing additional functionality to the products in which it is incorporated. This study was supported by the Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES, Finance Code 001), the Araucaria Foundation, and the National Council for Scientific and Technological Development (CNPq).