Banca de DEFESA: WELTON AARON DE ALMEIDA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : WELTON AARON DE ALMEIDA
DATE: 30/10/2023
TIME: 09:00
LOCAL: Google meet
TITLE:

INVESTIGATION OF ANTIMICROBIAL AND INSECTICIDAL ACTIVITIES OF PREPARATIONS OF Plectranthus barbatus LEAVES

KEY WORDS:

Aedes aegypti; trypsin inhibitor; lectin; Plectranthus barbatus; Streptococcus pyogenes

PAGES: 100
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Infecciosas de Animais
SUMMARY:

Plectranthus barbatus (Lamiaceae), known as falso boldo, is used in folk medicine and has been reported as a source of antioxidant compounds as well as anti-inflammatory, antimicrobial and acetylcholinesterase inhibitor activities. In this sense, this Thesis hypothesized that preparations of P. barbatus leaves may be active against disease-causing microorganisms and the larval stage of mosquito vectors of arboviruses. Thus, the aim of this work was to characterize preparations (extract, infusion and decoction) of P. barbatus leaves regarding the presence of secondary metabolites and proteins (lectins and trypsin inhibitors) and to investigate them regarding their antimicrobial potential for pathogenic bacteria, as well as larvicidal for Aedes aegypti. For this, a leaf extract in 0.15 M NaCl was obtained, as well as a decoction and an infusion in distilled water. The three preparations were investigated for antimicrobial activity by the plate microdilution method. The MIC (minimum inhibitory concentration) of the extract for Streptococcus pyogenes was determined, as well as its effect on the viability and morphology of bacterial cells by flow cytometry and synergistic action using commercial antibiotics. Then, extract, infusion and decoction were studied for their effect on the survival of A. aegypti larvae in the third instar (L3), and characterized for the presence of secondary metabolites, lectins and trypsin inhibitors. The effect of the extract on the activity of digestive proteases, permeability of the peritrophic membrane and morphophysiology of the midgut of L3, as well as on the growth of the gut microbiota and on melanogenesis were determined. The treatment with infusion and decoction did not interfere with the growth and survival of pathogenic bacteria, while the extract only inhibited the growth of S. pyogenes (MIC of 2.0 mg/mL). Flow cytometry revealed that most bacterial cells were viable, indicating a predominant bacteriostatic effect. On the other hand, FL1 vs. FL3 show that in treatments with the extract there were shifts of cells to higher values of FL3-H, indicating cell damage. The extract in combination with the antibiotics Cephalexin and Ciprofloxacin showed an indifferent effect against S. pyogenes. When investigated as larvicidal agents, the extract killed L3 (0.48% LC50, m/v), while the decoction and infusion did not affect larvae survival. HPLC analysis identified caffeic acid and flavonoids in the three preparations. A ribose/galactose binding lectin and polypeptides with trypsin inhibitory activity (34, 63 and 66 kDa) resistant to hydrolysis by L3 gut proteases were found in the extract. Incubation of the extract with larval proteases did not change lectin and trypsin inhibitor activities. The treatment of L3 with the extract at LC50 increased the permeability of the peritrophic membrane and prevented the larvae from passing to the fourth instar. The midgut morphology of the larvae was not affected by the extract, but the content of neutral polysaccharides in the epithelial cells was reduced. The extract stimulated in vitro the proliferation of the gut microbiota of L3 and increased in vivo the production of melanin by the larvae. Heating (100°C, 5 h) of the extract led to an increase in lectin, trypsin inhibitor and larvicidal activities. In conclusion, the saline extract was the preparation of P. barbatus leaves with better activity, constituting a new plant bioproduct with pharmacological potential for inhibiting growth and causing cell damage in S. pyogenes, and larvicide for inhibiting digestive proteases, damaging the morphophysiology of the midgut and induce dysbiosis, causing the death of L3. The results suggest that this activity may be linked to the presence of lectin and trypsin inhibitor.

COMMITTEE MEMBERS:
Presidente - EMMANUEL VIANA PONTUAL
Externa à Instituição - LÍVIA LAÍS DE SANTANA SILVA BARBOSA - UFPE
Externa à Instituição - MICHELE DALVINA CORREIA DA SILVA - UFERSA
Interno - ***.154.024-** - NATALY DINIZ DE LIMA SANTOS - UFRPE
Externo à Instituição - THIAGO HENRIQUE NAPOLEÃO - UFPE