Banca de DEFESA: LUCAS GABRIEL PITA DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LUCAS GABRIEL PITA DOS SANTOS
DATE: 10/01/2025
TIME: 09:00
LOCAL: Sala de seminário CEGOE
TITLE:

CHEMICAL CHARACTERIZATION OF LEAF PREPARATIONS OF Annona squamosa L. AND INVESTIGATION OF INSECTICIDE AND ANTIMICROBIAL POTENTIAL

KEY WORDS:

Bibliometric analysis; custard apple; dengue mosquito; maize weevil; non-target toxicity; insecticidal formulation.

PAGES: 107
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Saneamento Aplicado a Saúde do Homem
SUMMARY:

Plant metabolites have garnered growing interest for their potential in biotechnology, with applications in health and pest control. Annona squamosa L. (Annonaceae), commonly known as sugar apple, is a medicinal plant with edible fruits. This thesis aimed to:  I. Analyze current trends in the use of natural products for the control of insects of health importance (Aedes aegypti) and economic relevance (Sitophilus zeamais and Nasutitermes corniger); II. Obtain and characterize the saline extract from A. squamosa leaves regarding its chemical composition; III. Evaluate the insecticidal potential of the extract against Ae. aegypti, S. zeamais, and N. corniger; IV. Develop a solid formulation of the extract and assess its efficacy; V. Investigate the extract’s activity against bacteria associated with caprine mastitis. Dried and ground A. squamosa leaves were homogenized in a 0.15 M NaCl solution to obtain the extract, whose composition was determined through biophysical techniques such as thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Protein concentration in the extract and protease inhibitory activity were determined by spectrophotometry using colorimetric methods. The presence of lectins was investigated through their ability to agglutinate rabbit erythrocytes. The effects of the extract were evaluated on third-instar larvae (L3) of Ae. aegypti, adults of S. zeamais and N. corniger, as well as non-target toxicity to the microcrustacean Hyalella sp. The permeability of the peritrophic membrane of Ae. aegypti L3 after extract treatment was determined by activated charcoal diffusion into the ectoperitrophic space. Tablets based on the extract were produced and characterized by differential thermal analysis (DTA) and Fourier-transform infrared spectroscopy (FTIR). The effects of these tablets on the survival and midgut morphology of Ae. aegypti L3 were assessed by light microscopy. Additionally, the antibacterial potential of the extract was tested against isolates associated with caprine mastitis using the microdilution method. Bibliometric analysis revealed that research on natural insecticides is concentrated in tropical regions, where diseases transmitted by Ae. aegypti are more common. Furthermore, the use of metal nanoparticles derived from plant extracts has grown as a strategy to enhance stability and efficacy. TLC and HPLC identified cinnamic acid derivatives, rutin, and chlorogenic acid as the major metabolites in the extract. Proteins (22.9 mg/mL), including a trypsin inhibitor (15.6 U/mg) and lectin (21,333.33 HUAS), were also detected. The extract killed (LC50 = 1.9% w/v) and altered the permeability of the peritrophic membrane of Ae. aegypti L3. In adults of S. zeamais, the extract exhibited a strong feeding deterrent effect, killing 51.2% to 63.8% of the insects through starvation. No toxicity was observed for *N. corniger*; however, *Hyalella sp.* individuals were sensitive to the treatment. DTA revealed an exothermic event (450 °C) indicating degradation of extract components, and FTIR showed the presence of secondary amines (N-H stretch) and aliphatic compounds (C-N stretch), potentially reflecting protein content. These characteristics persisted in binary mixtures of the extract with excipients, indicating no alteration of the extract’s physicochemical properties. Treatment with the tablets killed 47% of Ae. aegypti L3 and caused epithelial hypertrophy and apocrine vesicle synthesis in the midgut of the larvae. The bacteria isolated from caprine mastitis were not sensitive to treatment with the extract. In conclusion, the insecticidal effect of A. squamosa leaf extract on Ae. aegypti L3 and S. zeamais adults may be linked to the presence of lectins, trypsin inhibitors, rutin, and chlorogenic acid, involving increased peritrophic membrane permeability and strong feeding deterrent effects, respectively. The tablet formulation of the leaf extract was effective against Ae. aegypti L3 due to structural and functional damage to the larvae’s midgut. Finally, caution is advised when using the extract due to the high non-target toxicity observed.

COMMITTEE MEMBERS:
Presidente - EMMANUEL VIANA PONTUAL
Interna - TATIANA SOUZA PORTO
Externa à Instituição - ISABELLA COIMBRA VILA NOVA - UFPE
Externo à Instituição - THIAGO HENRIQUE NAPOLEÃO - UFPE
Externo à Instituição - WELTON AARON DE ALMEIDA - UFRPE