Amyloid-ß oligomers in cellular models of Alzheimer's disease.

Amyloid-ß (Aß) dysmetabolism is tightly associated with pathological processes in Alzheimer's disease (AD). Currently, it is thought that, in addition to Aß fibrils that give rise to plaque formation, Aß aggregates into non-fibrillar soluble oligomers (AßOs). Soluble AßOs have been extensively studied for their synaptotoxic and neurotoxic properties. In this review, we discuss physicochemical properties of AßOs and their impact on different brain cell types in AD. Additionally, we summarize three decades of studies with AßOs, providing a compelling bulk of evidence regarding cell-specific mechanisms of toxicity. Cellular models may lead us to a deeper understanding of the detrimental effects of AßOs in neurons and glial cells, putatively shedding light on the development of innovative therapies for AD.

HPLC-DAD for the determination of three different classes of antifungals: method characterization, statistical approach, and application to a permeation study.

This study describes and characterizes methods for high-performance liquid chromatography diode array detection (HPLC-DAD) analysis of formulations containing molecules with antifungal activity of three different classes: terbinafine and butenafine (allylamines), miconazole and fluconazole (azoles), and geraniol, neral and geranial (monoterpenes). All methods used the same chromatographic column (RP18 ), enabling the analysis to be performed in a single batch. The specificity was extensively discussed through the establishment of purity peak methods. The analytical parameters (linearity, precision and accuracy) were calculated and discussed in detail using specific statistical approaches. All substances showed satisfactory results for chromatographic and analytical parameters. Limits of 1.3% to mean repeatability and 2.0% for intermediate precision are suggested as acceptance criteria in validation of methods by HPLC-DAD, in situations where there is no extensive pretreatment of the samples. The methods proved to be robust and significant factors were discussed regarding their influence on chromatographic parameters (retention time, resolution, tailing factor and column efficiency). Finally, the application of the developed methods was demonstrated by the results of a permeation study of the antifungal agents through bovine hoof membranes.

Synthesis and antileukemic activity of an ursolic acid derivative: A potential co-drug in combination with imatinib.

Imatinib, a specific Bcr-Abl tyrosine kinase inhibitor, is the most commonly used drug in the treatment of chronic myeloid leukemia. However, optimal response is not achieved in up to 33% of patients. Therefore, development of novel therapeutic strategies for chronic myeloid leukemia is critical. Betulinic (1) and ursolic (2) acids are natural pentacyclic triterpenes that exhibit antileukemic activities. In this study, we evaluated the effects of pharmacomodulations at the C-3 position of the triterpene moiety of betulinic and ursolic acids on their activity against K562 leukemia cells. Six new derivatives (1a-2c) were synthesized and evaluated for pro-apoptotic and anti-proliferative effects in mammalian and leukemic cells. 2c derivative containing an amine group at the C-3 position of ursolic acid was the most active against leukemia cells with an IC50 value of 5.2 µM after 48 h of treatment. 2c did not exhibit cytotoxic effects against VERO and HepG2 cells and human lymphocytes, showing a good selectivity index for cancer over normal cells. Induced cell death by apoptosis via caspases 3 and 8, and also caused cell cycle arrest as evidenced by accumulation of cells in the G1 phase and decreased cell population in the G2 phase. Furthermore, co-treatment of 2c with imatinib, the chemotherapy drug most commonly used to treat leukemia, resulted in a synergistic effect. Our findings provide a strong rationale for further investigation of combination therapy using the 2c derivative and imatinib in pre-clinical studies.

Modeling Diet-Induced Metabolic Syndrome in Rodents.

Standardized animal models represent one of the most valuable tools available to understand the mechanism underlying the metabolic syndrome (MetS) and to seek for new therapeutic strategies. However, there is considerable variability in the studies conducted with this essential purpose. This review presents an updated discussion of the most recent studies using diverse experimental conditions to induce MetS in rodents with unbalanced diets, discusses the key findings in metabolic outcomes, and critically evaluates what we have been learned from them and how to advance in the field. The study includes scientific reports sourced from the Web of Science and PubMed databases, published between January 2013 and June 2020, which used hypercaloric diets to induce metabolic disorders, and address the impact of the diet on metabolic parameters. The collected data are used as support to discuss variables such as sex, species, and age of the animals, the most favorable type of diet, and the ideal diet length to generate metabolic changes. The experimental characteristics propose herein improve the performance of a preclinical model that resembles the human MetS and will guide researchers to investigate new therapeutic alternatives with confidence and higher translational validity.

Betulinic Acid and Brosimine B Hybrid Derivatives as Potential Agents against Female Cancers.

BACKGROUND: Cancer is a multifactorial disease, representing one of the leading causes of death worldwide. On a global estimate, breast cancer is the most frequently occurring cancer in women and cervical cancer, the fourth most common. Both types of cancer remain the major cause of cancer-related mortality in developing countries. A strategy for rational drug design is hybridization, which aims to bring together in one molecule, two or more pharmacophores in order to reach several biological targets. OBJECTIVE: The objective of this work was to develop new hybrids based on natural pharmacophores: Betulinic acid (1) and brosimine b (2), active in female cancer cell lines. METHODS: The coupling reactions were carried out by Steglich esterification. Different compounds were designed for the complete and simplified structural hybridization of molecules. The anticancer activities of the compounds were evaluated in human cervical adenocarcinoma (HeLa), human cervical metastatic epidermoid carcinoma (ME-180), and human breast adenocarcinoma (MCF-7) cell lines. RESULTS: Hybrid 3 presented higher potency (IC50 = 9.2 ± 0.5µM) and SI (43.5) selectively in MCF-7 cells (in relation to Vero cells) with its cytotoxic effect occurring via apoptosis. In addition, compound 6 showed activity in MCF-7 and HeLa cells with intermediate potency, but with high efficacy, acting via apoptosis as well. CONCLUSION: In this context, we showed that the combination of two complex structures generated the development of hybrids with differing inhibitory profiles and apoptotic modes of action, thus representing potential alternatives in female cancer treatment.

SERCA plays a crucial role in the toxicity of a betulinic acid derivative with potential antimalarial activity.

Malaria is one of the most significant infectious diseases that affect poor populations in tropical areas throughout the world. Plants have been shown to be a good source for the development of new antimalarial chemotherapeutic agents, as shown for the discovery of quinine and artemisinin derivatives. Our research group has been working with semisynthetic triterpene derivatives that show potential antimalarial activity toward different strains of Plasmodium falciparum by specifically modulating calcium pathways in the parasite. Promising results were obtained for nanomolar concentrations of the semisynthetic betulinic acid derivative LAFIS13 against the P. falciparum 3D7 strain in vitro, with a selectivity index of 18 compared to a mammalian cell line. Continuing these studies, we present here in vitro and in vivo toxicological evaluations of this compound, followed by docking studies with PfATP6, a sarco/endoplasmic reticulum Ca+2-ATPase (SERCA) protein. LAFIS13 showed an LD50 between 300 and 50 mg/kg, and the acute administration of 50 mg/kg (i.p.) had no negative effects on hematological, biochemical and histopathological parameters. Based on the results of the in vitro assays, LAFIS13 not exerted significant effects on coagulation parameters of human peripheral blood, but a hemolytic activity was verified at higher concentrations. According to the molecular docking study, the PfATP6 protein may be a target for LAFIS13, which corroborates its previously reported modulatory effects on calcium homeostasis in the parasite. Notably, LAFIS13 showed a higher selectivity for the mammalian SERCA protein than for PfATP6, thus impairing the selectivity between parasite and host. In summary, the direct interaction with calcium pumps and the hemolytic potential of the compound proved to be plausible mechanism of LAFIS13 toxicity.

Design, Synthesis and Biological Evaluation of Betulinic Acid Derivatives as New Antitumor Agents for Leukemia.

BACKGROUND: Chronic myeloid leukemia (CML) is currently treated with imatinib, a Bcr-Abl inhibitor. However, resistance to this drug usually develops over time. Triptolide, a diterpenoid triepoxide, has been shown active against CML cells resistant to imatinib, acting mainly on the level of Bcr-Abl transcription inhibition. OBJECTIVE: Here, we used the triterpene betulinic acid, a known proteasome inhibitor with potential antileukemic activity, as a scaffold for the generation of analogues with predicted triptolide biological activity. METHOD: Betulinic acid derivatives were designed based on the structure-activity relationship of triptolide and evaluated for their cytotoxic effects in CML cells, lymphocytes and human keratinocytes (HaCaT), as well as against the proteasome complex. The main modification performed on betulinic acid was fluorination at C-28 and epoxidation, both of which are responsible for enhancing activity of triptolide. A total of 10 compounds were obtained: 6 previously described and 4 novel compounds. The cytotoxic activity over a CML cell line (K562) was assessed using flow cytometry and compared to lymphocytes and HaCaT. RESULT: The results show that betulinic acid was the most cytotoxic compound against CML cells, showing a good selectivity index for cancer over normal cells. The most important trend for the activity in betulinic acid derivatives is the presence of a free hydroxyl group at C-3 and a carboxyl group at C-28. Results also indicated that the epoxide is important for enhancing the activity, while modification at C-28 worsens the activity. CONCLUSION: Proteasome inhibition assays suggest that proteasome is the main target for betulinic acid and its derivatives.

HPLC method for the determination of ecdysterone in extractive solution from Pfaffia glomerata.

A RP-LC method was developed and validated to quantify ecdysterone in extractive solution from subterraneous parts of Pfaffia glomerata. The analysis was performed using a RP-18 column with acetonitrile:water isocratic elution and the detection was carried out by UV at 242 nm. The standard curve for ecdysterone was linear over the range of 5.2-41.6 microg/ml (R2=0.9995). The extractive solution showed linear response in the range of 25.05-175.35 microg/ml (R2=0.9977). This method showed excellent repeatability (relative standard deviation, R.S.D.<2.0%), intermediary precision (R.S.D.=2.13%) and accuracy (101.04; R.S.D.=1.51%). The limit of detection (LOD) was 0.036 microg/ml and the limit of quantification (LOQ) was 0.110 microg/ml, demonstrating the sensitivity of the method. This assay can be readily utilized as quality controlled method for P. glomerata preparations.

Hypnotic effect of ecdysterone isolated from Pfaffia glomerata (Spreng.) Pedersen / Efeito hipinótico de ecdisterona isolada de Pfaffia glomerata (Spreng.) Pedersen

Neste trabalho foi avaliado, em roedores, o efeito depressor das frações clorofórmio (CHCl3), acetato de etila (EtOAc) e n-butanol, obtidas das partes subterrâneas de Pfaffia glomerata, empregando-se o teste de tempo de sono barbitúrico como referência. Somente a fração lipofílica (CHCl3:EtOAc, 1:1, m/m) (i.p. 500 mg/kg; v.o. 1000 mg/kg) potenciou o tempo de sono induzido por pentobarbital. A ecdisterona foi isolada e identificada como constituinte majoritário (1,4 por cento m/m) desta fração, através de cromatografia líquida de alta eficiência e métodos espectroscópicos, respectivamente. Este composto potenciou o tempo de sono barbitúrico (100 mg/kg, i.p.; 400 mg/kg, v.o), sem causar hipotermia. Nestas mesmas doses, a ecdisterona não alterou a performance dos animais no rota-rod, esquiva inibitória e labirinto em cruz-elevado, além de não alterar o padrão de convulsões induzidas por pentilenotetrazol. Este perfil indica que esta substância, nestas doses, não apresenta perfil ansiolítico ou neurotóxico. Estes resultados indicam que a ecdisterona é o componente responsável pela ação hipnótica apresentada pela fração lipofílica obtida das partes subterrâneas de P. glomerata.

In this study the depressant effect of fractions from P. glomerata was initially evaluated using the mice barbiturate sleeping time test as reference. The fractions tested were the CHCl3, the EtOAc, the n-BuOH and the aqueous fraction obtained from P. glomerata subterraneous parts. Only the pretreatment with the lipophilic fraction (CHCl3: EtOAc, 1:1, w/w) increased the barbiturate sleeping time (i.p 500 mg/kg; v.o. 1000 mg/kg). Ecdysterone, the main substance isolated from this lipophilic fraction, was identified by spectroscopic methods and its content in the ethanol extract was determined as 1.4 percent (w/w) by HPLC. In order to investigate the hypothesis of ecdysterone displaying a depressant effect on nervous central system, an evaluation toward the hypnotic-sedative and anxiolytic effects of this drug was carried out. Ecdysterone 100 mg/kg, i.p, increased the barbiturate sleeping time without provoking hypothermia; when administered by oral route its minimal effective dose was 400 mg/kg. On the other hand, ecdysterone (100 mg/kg, i.p; 400 mg/kg, p.o) did not impair motor coordination and was ineffective on pentylenetetrazole-induced convulsion, elevated plus-maze and step-down inhibitory avoidance tests, indicating that at these doses the drug does not present an anxiolytic profile and does not cause manifest neurotoxic effects as well. In conclusion, the lipophilic fraction from P. glomerata presents a hypnotic effect being ecdysterone one of the compounds responsible for this CNS activity.