Evaluation of guanylhydrazone derivatives as inhibitors of Candida rugosa digestive lipase: Biological, biophysical, theoretical studies and biotechnological application.

This work aimed to evaluate the inhibition of Candida rugosa lipase by five guanylhydrazone derivatives through biological, biophysical and theoretical studies simulating physiologic conditions. The compound LQM11 (IC50 = 14.70 µM) presented the highest inhibition against the enzyme. Therefore, for a better understanding of the interaction process, spectroscopic and theoretical studies were performed. Fluorescence and UV-vis assays indicate a static quenching mechanism with non-fluorescent supramolecular complex formation and changing the native protein structure. The binding process was spontaneous (ΔG < 0) and electrostatic forces (ΔH < 0 and ΔS > 0) played a preferential role in stabilizing the complex ligand-lipase. The compounds were classified as non-competitive inhibitors using orlistat as a reference in competition studies. Based on the 1H NMR assays it was possible to propose the sites of ligand (epitope) that bind preferentially to the enzyme and the theoretical studies were consistent with the experimental results. Finally, LQM11 was efficient as a lipase inhibitor of the crude intestinal extract of larvae of Rhynchophorus palmarum, an important agricultural plague, showing potential for control of this pest. Within this context, the real potential of this biotechnological application deserves further studies.

Embryonic development of Rhynchophorus palmarum (Coleoptera: Curculionidae): dynamics of energy source utilization.

Energy homeostasis is an essential process during oogenesis, nutrients are required for suitable embryonic development, and recently, studies have investigated metabolic activity during this process. This work aims the investigation of dynamics of energy source utilization of Rhynchophorus palmarum during embryogenesis. For this, we first evaluated the mobilization kinetics of the lipids and glycogen. Thereafter, the synthesis of RNA, protein, and the involvement of enzyme of the glycolytic and pentose-phosphate pathways. Results showed that lipid content decreased in contrast with the lipase activity. The total glycogen amounts it was partly consumed and the glucose content increased, but then values remained stable until hatching. Total RNA content increased, and no significant changes in total protein content were observed. A study of the glycolytic pathway data showed activity of hexokinase and pyruvate kinase at the beginning of embryogenesis. Furthermore, glucose-6-phosphate formed is driven into the pentose-phosphate pathway viewed the high activity of glucose-6-phosphate dehydrogenase. Finally, these results showed that mobilization of different energy sources together with different enzymatic activities has an important role in embryonic development of R. palmarum.

Interaction between bioactive compound 11a-N-tosyl-5-deoxi-pterocarpan (LQB-223) and Calf thymus DNA: Spectroscopic approach, electrophoresis and theoretical studies.

The interaction of small molecules with DNA has been quite important, since this biomolecule is currently the major target for a wide range of drugs in clinical use or advanced clinical research phase. Thus, the present work aimed to assess the interaction process between the bioactive compound 11a-N-tosyl-5-carba-pterocarpan, (LQB-223), that presents antitumor activity, with DNA, employing spectroscopic techniques, electrophoresis, viscosity and theoretical studies. Through UV-vis and molecular fluorescence spectroscopy, it was possible to infer that the preferential quenching mechanism was static, characterized by non-fluorescent supramolecular complex formation between the LQB-223 and DNA. The binding constant was 1.94∙103Lmol-1 (30°C) and, according to the thermodynamic parameters, the main forces involved in the interaction process are hydrophobic. Potassium iodide assay, competition with ethidium bromide, fluorescence contact energy transfer and melting temperature profile of DNA were employed to evaluate the binding mode. Except for KI assay, all results obtained indicated minor groove as the preferential binding mode of LQB-223 to DNA. These observations were supported by ionic strength assay, viscosity and molecular dynamics and docking studies. Finally, electrophoresis analysis demonstrated that the interaction does not promote DNA fragmentation, but it leads to variation in the migration profile after increasing the ligand concentration.