Banca de DEFESA: REBECA DIAS DOS SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : REBECA DIAS DOS SANTOS
DATE: 10/03/2025
TIME: 14:00
LOCAL: Plataforma digital
TITLE:

Determination of the antioxidant and antibacterial activity of the essential oils of guava (Psidium guajava), pitanga (Eugenia uniflora) and their nanoemulsions

KEY WORDS:

nanoformulation; volatile oils; antimicrobial activity; stability studies; time-death curve.

PAGES: 60
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

Guava (Psidium guajava) and pitanga (Eugenia uniflora) belong to the Myrtaceae family and the essential oils extracted from their leaves have antimicrobial, antiinflammatory and antioxidant properties. These characteristics give them great potential for application in the food, cosmetics and pharmaceutical industries. However, the application of essential oils is often limited due to their volatility, low water solubility and instability under various environmental conditions. To overcome these challenges, nanoemulsions have emerged as an innovative solution, capable of improving the stability and bioavailability of essential oils. The aim of this study was to develop gel nanoemulsions of guava and pitanga essential oils and to determine the antioxidant and antimicrobial activity of the essential oils and nanoemulsions. The chemical characterization of the guava and pitanga essential oils was carried out using gas chromatography coupled with mass spectrometry, the quantification of total phenolic compounds was determined using the Folin-Ciocalteau method and the antioxidant activity using the ABTS (2,2-diphenyl-1-picrylhydrazyl) and DPPH (2,2-azinobs-3- ethylbenzthiazoline-6-sulfonic acid) methods. The nanoemulsions were prepared and characterized using analyses of droplet size, polydispersity index (PDI), zeta potential and pH. The stability of the nanoemulsions was studied for 30 days at different temperatures (4°C, 40°C and 25°C). The antimicrobial activity of the essential oils and nanoemulsions was determined using the following methodologies: agar diffusion method; determination of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). The tests to inhibit microbial growth over time of the essential oils and nanoemulsions were carried out against Staphylococcus aureus and Escherichia coli. The main chemical compounds in pitanga essential oil were curzerene (34.80%) and germacrene B (11.92%), while guava essential oil showed β-caryophyllene (25.92%), β-selinene (22.64%) and γ-selinene (19.13%). The pitanga and guava nanoemulsions had droplet sizes of 105.30 and 99.50 nm, PDI values of 0.32 and 0.43 and zeta potential of -9.29 and -7.34 mV, respectively. These nanoemulsions remained stable for 30 days of storage at 25 °C, with droplet sizes of 104.7 and 103.8 nm, PDI values below 0.50 and no phase separation. The pitanga nanoemulsion exhibited inhibition zones ranging from 8.41 to 15.13 mm against the bacteria S. aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii. In addition, the pitanga nanoemulsion showed the largest zones of inhibition against Candida albicans (20.97 mm) and Candida krusei (15.20 mm), along with low values of minimum inhibitory concentration (MIC) (0.54-1.22 mg/mL) and minimum bactericidal concentration (MBC) (4.84-11.02 mg/mL) against these potentially pathogenic yeasts. The guava nanoemulsion showed low MIC (1.26 mg/mL) and MBC (11.35 mg/mL) values for C. krusei. The microbial growth inhibition test over time also suggested the efficacy of the nanoemulsions against S. aureus and E. coli, highlighting their potential as a new alternative therapeutic agent.

COMMITTEE MEMBERS:
Presidente - 1697332 - DANIELA CASTILHO ORSI
Externa ao Programa - 1750177 - LIVIA CRISTINA LIRA DE SA BARRETO - UnBExterna à Instituição - CALLIANDRA MARIA DE SOUZA SILVA - UnB
Externa à Instituição - VANIA SILVA CARVALHO - IFGOIANO