BACE-1 and γ-Secretase as Therapeutic Targets for Alzheimer's Disease.

Alzheimer's disease (AD) is a growing global health concern with a massive impact on affected individuals and society. Despite the considerable advances achieved in the understanding of AD pathogenesis, researchers have not been successful in fully identifying the mechanisms involved in disease progression. The amyloid hypothesis, currently the prevalent theory for AD, defends the deposition of ß-amyloid protein (Aß) aggregates as the trigger of a series of events leading to neuronal dysfunction and dementia. Hence, several research and development (R&D) programs have been led by the pharmaceutical industry in an effort to discover effective and safety anti-amyloid agents as disease modifying agents for AD. Among 19 drug candidates identified in the AD pipeline, nine have their mechanism of action centered in the activity of ß or γ-secretase proteases, covering almost 50% of the identified agents. These drug candidates must fulfill the general rigid prerequisites for a drug aimed for central nervous system (CNS) penetration and selectivity toward different aspartyl proteases. This review presents the classes of γ-secretase and beta-site APP cleaving enzyme 1 (BACE-1) inhibitors under development, highlighting their structure-activity relationship, among other physical-chemistry aspects important for the successful development of new anti-AD pharmacological agents.

Dynamic flow-through approach to evaluate readily bioaccessible antioxidants in solid food samples.

Release of bioactive compounds from food matrices is regarded as the first step towards their human bioavailability. The objective of this work was the implementation of an affordable and robust flow-through device for expedient dynamic leaching experiments aiming at the assessment of readily bioaccessible antioxidant compounds in solid food commodities. A simple configuration is proposed using commercially available devices containing regenerated cellulose filters placed in polypropylene holders to entrap the solid sample, featuring a disposable, single use extraction chamber. The kinetic extraction profile of fast leachable antioxidants from different food matrices was evaluated using the ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) assay, fitting a first-order reaction model for readily bioaccessible compounds (R>0.9). The leaching rate constant values associated to the fast leachable antioxidant compounds were 0.060-0.446min-1 and 0.105-0.210min-1 for water and ethanol/water (1:1, v/v) applied as extractants, respectively. Furthermore, no statistically significant differences were found between the estimated values of bioaccessible antioxidant compounds by the kinetic model and the values attained using conventional batch-wise extraction methodology, ranging from 3.37 to 60.3 µmol of Trolox ((±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) per g of sample. Extension of the method using U. S. Pharmacopeia surrogate biological media (stomach (pH 1.2) and intestinal (pH 7.5) fluids without enzymes) to NIST-1570a spinach leaves provided gastrointestinal compartment-dependent kinetic leaching rates (0.120 and 0.198min-1, respectively) and total antioxidant content (45.5 and 52.5µmol of Trolox per g of sample, respectively).

Rapid assessment of endpoint antioxidant capacity of red wines through microchemical methods using a kinetic matching approach.

Antioxidant capacity of food samples is usually assessed by different analytical methods, however the results attained even for the same method are strongly dependent on the selected reaction time and also on the standard compound used. To tackle this problem, we propose here a kinetic matching approach, associated to the conversion of results into equivalents of a common standard compound, as a universal way for expression of results. The methodology proposed was applied to methods based on different chemistries (Folin-Ciocalteu (F-C), CUPRAC, DPPH(•) and ABTS(•+) assays) and red wines (n=40) were chosen as a model of complex food sample. For implementation of the kinetic matching approach, the standard phenolic mixture (caffeic acid, (+)-catechin, hesperetin, morin and (-)-epigallocatechin gallate) was chosen for calibration in F-C, CUPRAC and DPPH(•) assays, while tannic acid was suitable for ABTS(•+) assay. Results showed that, for all methods, there was no statistical difference between results attained by the kinetic matching approach (after <10 min of reaction) and that at endpoint conditions (after 60 to 300 min). The repeatability and the reproducibility of the kinetic matching approach was <4.5%, for all antioxidant assays. The sample throughput increases from <18 (endpoint measurements) to >108 h(-1) using the proposed kinetic approach. Moreover, we have established here a way of converting results to equivalents of a common standard, providing values independent of its kinetic profile, by using the ratio between calibration sensitivities performed at endpoint conditions.