Martins D. de Cerqueira

Oxidative Stress in Neurodegenerative Diseases: Mechanisms and Therapeutic Perspectives

The incidence and prevalence of neurodegenerative diseases (ND) increase with life expectancy. This paper reviews the role of oxidative stress (OS) in ND and pharmacological attempts to fight against reactive oxygen species (ROS)-induced neurodegeneration. Several mechanisms involved in ROS generation in neurodegeneration have been proposed. Recent articles about molecular pathways involved in ROS generation were reviewed. The progress in the development of neuroprotective therapies has been hampered because it is difficult to define targets for treatment and determine what should be considered as neuroprotective. Therefore, the attention was focused on researches about pharmacological targets that could protect neurons against OS. Since it is necessary to look for genes as the ultimate controllers of all biological processes, this paper also tried to identify gerontogenes involved in OS and neurodegeneration. Since neurons depend on glial cells to survive, recent articles about the functioning of these cells in aging and ND were also reviewed. Finally, clinical trials testing potential neuroprotective agents were critically reviewed. Although several potential drugs have been screened in in vitro and in vivo models of ND, these results were not translated in benefit of patients, and disappointing results were obtained in the majority of clinical trials.

Seasonal variation and antimicrobial activity of Myrcia myrtifolia essential oils

This work reports the seasonal variation of the composition of leaf volatile oils and the composition of volatile oils from flowers and fruits of Myrcia myrtifolia DC harvested in the sand dunes of Salvador, Bahia, northeastern region of Brazil between 2002 and 2003. The oils were analyzed by GC-FID and GC-MS so that 28 components were identified. a-Pinene was predominant in a range from 61.5 to 90.9% in all samples analyzed. The leaf oil collected in October 2002 had their antimicrobial properties tested against six bacteria, two yeasts and five filamentous fungi being active against Staphylococcus aureus, methicilin-resistant Staphylococcus aureus, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, and showed strongest activity against Microsporum canis and Trichophyton rubrum. The oil displayed moderate toxicity against Artemia salina showing a LC50 of 479.16 µg mL-1.

Variação sazonal da composição do óleo essencial de Myrcia salzmannii Berg. (Myrtaceae)

This work report the seasonal variation of composition of the volatile oils from leaves and from flowers of Myrcia salzmannii harvested in the sand dunes of Salvador, Bahia, northeastern region of Brazil in the years 2001 and 2003. The oils were analyzed by GC-FID and GC-MS being identified 49 components. Nine essential oil samples of leaves collected on different months and years and one sample of flowers were analyzed. β-Caryophyllene and α-humulene were the only compounds present in all of the samples being the first the majority compound.

8-Methoxypsoralen is a competitive inhibitor of glutathione S-transferase P1-1

The blood-brain barrier (BBB) is known to protect healthy brain cells from potentially dangerous chemical agents, but there are many evidences supporting the idea that this protective action is extended to tumor cells. Since the process of angiogenesis in brain tumors leads to BBB breakdown, biochemical characteristics of the BBB seem to be more relevant than physical barriers to protect tumor cells from chemotherapy. In fact, a number of resistance related factors were already demonstrated to be component of both BBB and tumor cells. The enzyme glutathione S-transferases (GST) detoxify electrophilic xenobiotics and endogenous secondary metabolites formed during oxidative stress. A role has been attributed to GST in the resistance of cancer cells to chemotherapeutic agents. This study characterized 8-methoxypsoralen (8-MOP) as a human GST P1-1 (hGST P1-1) inhibitor. To identify and characterize the potential inhibitory activity of 8-MOP, we studied the enzyme kinetics of the conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) with GSH catalyzed by hGST P1-1. We report here that 8-MOP competitively inhibited hGST P1-1 relative to CDNB, but there was an uncompetitive inhibition relative to GSH. Chromatographic analyses suggest that 8-MOP is not a substrate. Molecular docking simulations suggest that 8-MOP binds to the active site, but its position prevents the GSH conjugation. Thus, we conclude that 8-MOP is a promising prototype for new GST inhibitors pharmacologically useful in the treatment of neurodegenerative disorders and the resistance of cancer to chemotherapy.

Modes of Action of Arjunolic Acid and Derivatives on Trypanosoma cruzi Cells

Chagas disease causes considerable morbimortality in the Americas, with circa 7 to 8 million infected people, causing at least 12,000 annual deaths and 100 million people at risk. Its chemotherapy is poorly selective and effective, associated to severe side effects and unresponsive cases. Thus, R&D on therapeutic alternatives is undoubtedly required. The Brazilian poorly studied biodiversity offers uncountable bioagents, which may be exploited for chemotherapy. The triterpene arjunolic acid (AA), reduced the Trypanosoma cruzi epimastigote in vitro proliferation with an apparent IC₅₀ of 171 µM. Electron microscopy analysis revealed remarkable effects on the parasite surface and architecture. AA-treated parasites displayed minutely corrugated plasma membranes devoid of subpellicular microtubules as well as biogenesis of multiple basal bodies. As the AA effects appeared mainly restricted or originated at the parasite peripheral cytoplasm, including the cytoskeleton membrane linkage, we inferred that the compound targeted primarily the lipid bilayer; therefore, we performed synthetic modification to increase the molecule lipophilicity and thus membrane permeability. The methyl ester (MeAA) and tri-acetylated derivatives (3AcAA) had potentiated trypanocidal activity, producing IC₅₀ values of 21.9 and 15.8 µM, respectively. Both derivatives were able to produce remarkable ultrastructural alterations in the parasites, including inner compartments such as Golgi apparatus and the endocytic/autophagic pathway. Parasites cultured with both derivatives displayed numerous and large autophagic vacuoles, altered flagellar length and cell body connection. These data indicate that synthetically-modified natural products comprise valuable tools in antiparasitic chemotherapy and that electron microscopy may be useful not only in determining the mechanisms of action but also in directing such modifications for rational drug design.

Sensitized photooxygenation of Ent-Pimaradiene derivatives

Methyl esters of diterpenoids ent-pimara-9(11),15-dien-19-oic acid (1), ent-pimara-7,15-dien-19-oic acid (2), and ent-pimara-8,15-dien-19-oic acid (3) were submitted to photooxygenation reactions with sensitized singlet oxygen. While compounds 2 and 3 were converted to the products, compound 1 reacted only partially, suggesting an influence of the steric hindrance on the endocyclic double bond of 1. The oxidation products obtained, methyl-7a,11b-dihydroxypimara-8,15-dien-19-oate (5), methyl-7a-hydroperoxypimara-8(14),15-dien-19 oate (6), methyl-7a-hydroxy-14-oxopimara-15-en-19-oate (8), methyl-7a,9a-dihydroxypimara-8(14),15-dien-19-oate (9) and methyl-7a,14a-dihydroxypimara-8,15-dien-19-oate (10), are new and their structures were elucidated by spectral data analysis.