ABSTRACT Staphylococcus aureus is a Gram‐positive bacterium; it is an important source of food‐borne disease causing 241,000 illnesses per year only in the USA. Guava ( Psidium guajava L.) is a fruit tree native to South America that contains tannins, phlorotannins, saponins, terpenoids, alkaloids, and polyphenols; these last possess antioxidant and antimicrobial activity. The aim of this study was to evaluate the antioxidant and antimicrobial activity of guava leaves extracts against S. aureus . Guava leaves were used fresh (FL), dry (DL), and scalded (SL). Phenolic compounds were extracted with water (W); ethanol 50% and ethanol 80% were employed as solvents, and Soxhlet, ultrasonic, and maceration were used as extraction methods. Phenol content was measured by the Folin–Ciocalteu method, and the antioxidant (DPPH) and antimicrobial activity were evaluated according to Clinical & Laboratory Standards Institute procedures. Results showed that ultrasonic‐SL‐W, ultrasonic‐DL‐ethanol 50%, and Soxhlet‐SL‐ethanol 80% had 10.75, 6.38, and 3.41 mg GAE/g of total phenol content, respectively. The antioxidant capacity exhibited 0.33, 0.14, and 0.17 mg TE/g, respectively. These extracts showed antimicrobial activity, reaching inhibition zones of 2.0, 1.9‐, and 1.8‐mm, respectively. The ultrasound extraction method and scalding pretreatment improved the extraction and bioactivity in aqueous and ethanol extracts. Combining extraction techniques is an effective tool to obtain guava leaves extracts with antimicrobial activity against S. aureus .
Díaz-Galindo et al. (Fri,) studied this question.