Banca de DEFESA: MARIANA SANTOS DE MENDONÇA

Evaluation of the Antimicrobial and Antioxidant Activity of Different Extracts from the Bark of Jurema Preta (Mimosa tenuiflora)

Phenolic compounds, flavonoids, condensed tannin.

The Caatinga is a biome exclusively found in Brazil, predominantly in the northeastern region
of the country. It is characterized by a semi-arid climate and flora and fauna adapted to drought.
Among the various plant species found in the region, *Mimosa tenuiflora* (Willd.) Poir,
popularly known as black jurema, stands out in folk medicine for its antioxidant and
antimicrobial effects, due to its potential for the production of condensed tannins. This study
aimed to evaluate the antimicrobial and antioxidant activity, as well as the chelating capacity
of iron (Fe2+) and copper (Cu2+) metal ions, of different types of black jurema bark extracts.
The material was collected at the experimental farm of the Federal Rural University of
Pernambuco (UFRPE), in the municipality of Garanhuns-PE. The samples were subjected to
drying, grinding, and extraction: purified, ethanolic, and aqueous. Antimicrobial assays were
performed using the broth dilution method with two strains, Staphylococcus aureus 25923 and
Staphylococcus aureus PE 86. Antioxidant assays were performed using the DPPH and ABTS
methods, and copper and iron chelating activities were assessed. The extracts were analyzed at
concentrations of 62.5, 125, 250, 500, and 1000 μg/mL. The results showed that all extracts
exhibited significant antimicrobial activity, varying with the type of extract, concentration, and
bacterial strain, with results above 80% at intermediate concentrations. Inhibition against the
ATCC 25926 strain was highest for all three extracts, with values of 81.51% and 85.14% at
concentrations of 500 and 250 μg/mL, respectively, for the purified extract. And with values
of 82.95% and 84.49% for the ethanolic and aqueous extracts at a concentration of 500 μg/mL,
respectively. For the PE 86 strain, the antimicrobial inhibition was lower compared to the first
strain tested. The antioxidant activity, evaluated by the ABTS and DPPH methods, showed
values close to 84% at the highest concentrations, indicating high antioxidant capacity, with
greater efficiency for the ABTS assay. In the Fe chelating assay, the extracts showed similar
behavior, with values above 60% at the highest concentrations of 100, 500, and 250 μg/mL,
with a maximum of 62.80% at 500 μg/mL for the purified extract. Regarding Cu chelation, the
purified tannin showed 63.54% and 62.52% at concentrations of 1000 and 500 μg/mL,
respectively, decreasing sharply to 10.77% at a concentration of 62.5 μg/mL. The ethanolic and
aqueous extracts of tannin showed maximum values of 65.50% and 64.12% at 1000 μg/mL,
respectively. It is concluded that the condensed tannins from Mimosa tenuiflora bark have
significant antimicrobial, antioxidant, and chelating potential, regardless of the extraction
method, highlighting their applicability as a natural alternative.