Andrew G. Mercader

QSAR prediction of inhibition of aldose reductase for flavonoids

We performed a predictive analysis based on quantitative structure-activity relationships (QSAR) of an important property of flavonoids, which is the inhibition (IC(50)) of aldose reductase (AR). The importance of AR inhibition is that it prevents cataract formation in diabetic patients. The best linear model constructed from 55 molecular structures incorporated six molecular descriptors, selected from more than a thousand geometrical, topological, quantum-mechanical, and electronic types of descriptors. As a practical application, we used the obtained QSAR model to predict the AR inhibitory effect of newly synthesized flavonoids that present 2-, 7-substitutions in the benzopyrane backbone.

Predictive modeling of the total deactivation rate constant of singlet oxygen by heterocyclic compounds.

We constructed a predictive model of the total deactivation rate constant (k(t)) of singlet oxygen by heterocyclic compounds that are widespread in biological systems and participate in highly relevant biologic functions related with photochemical processes, by means of quantitative structure-property relationships (QSPR). The study of the reactivity of singlet oxygen with biomolecules provides their antioxidant capability, and the determination of the rate constants allows evaluation of the efficiencies of these processes. Our optimal linear model based on 41 molecular structures, which have not been used previously in a QSPR study, consists of six variables, selected from more than thousand geometrical, topological, quantum-mechanical and electronic types of molecular descriptors. Our recently developed strategy to determine the optimal number of descriptors in model is successfully applied. As a practical application of our QSPR model we estimated the unknown k(t) of several heterocyclic compounds that are of particular interest for further experimental studies in our research group.

Naturally-occurring dimers of flavonoids as anticarcinogens.

Biflavonoids are dimers of flavonoid moieties linked by a C-C or C-O-C bond. Simple, complex, rearranged, natural and ketalized Diels-Alder adducts, benzofuran derivatives, and spirobiflavonoids are some of the structural groups of biflavonoids. These compounds are mainly distributed in the Gymnosperms, Angiosperms (monocots and dicots), ferns (Pteridophyta), and mosses (Bryophyta). Biflavonoids have shown a variety of biological activities, including anticancer, antibacterial, antifungal, antiviral, antiinflammatory, analgesic, antioxidant, vasorelaxant, anticlotting, among others. This work is focused on probably the most potentially relevant biological activity of biflavonoids, the anticancer activity and the involved mechanisms of action, such as induction of apoptosis [inhibition of cyclic nucleotide phosphodiesterases; effects on NF-κB family of transcription factors; activation of caspase(s); inhibition effects on bcl-2 expression, and upregulation of p53 and caspase-3 gene expression]; inhibition of angiogenesis [anti-proliferative effects; activation of Rho-GTPases and ERK signaling pathways; inhibition of FASN activity]; inhibition of pre-mRNA splicing; inhibition of human DNA topoisomerases I and II-α; anti-inflammatory/ immunoregulatory effects [inhibition of XO; inhibition of proinflammatory enzymes, such as PLA2 and COX; effects on cytokines mediated COX-2 and iNOS expression]; modulation of immune response; inhibition of protein tyrosine phosphorylation; antioxidant and analgesic activities in relation to the anticarcinogen behavior. For that reason the structures and anticarcinogenic activities of 83 biflavonoids are thoroughly discussed. The results of this work indicate that biflavonoids strongly affect the cancer cells with little effect on normal cell proliferation, suggesting a therapeutic potential against cancer.

(Iso)Flav(an)ones, Chalcones, Catechins, and Theaflavins as Anticarcinogens: Mechanisms, Anti-Multidrug Resistance and QSAR Studies

Flavonoids have shown anticarcinogenic activity in cancer cell lines, animal models, and some human studies. Quantitative structure-activity relationship (QSAR) models have become useful tools for identification of promising lead compounds in anticancer drug development. However, epidemiological and clinical studies are still scarce. Compounds with flavonoid scaffold have been the subject of many mechanistic studies in cells, but information on human chemopreventive properties is still missing. The knowledge of the mechanisms of action, anti-multidrug resistance, and QSAR studies on flavonoids and related compounds may help to enhance research on these compounds and their bioactivity. Therefore, once the issue is introduced, the mechanisms involved, and QSAR studies developed to predict the activity and toxicity of these chemicals to biological systems are discussed. QSAR studies on flavonoids as inhibitors of breast cancer resistance protein (BCRP/ABCG2), 17β-hydroxysteroid dehydrogenase (17β-HSD), PIM-1 kinase and cyclin-dependent kinases (CDKs) are analyzed. Combined treatment of flavonoids with TRAIL and current chemotherapy agents is also discussed as a promising cancer chemoprevention and/or therapy.

Different encoding alternatives for the prediction of halogenated polymers glass transition temperature by quantitative structure-property relationships

ABSTRACT The glass transition temperature, Tg, is one of the most important properties of amorphous polymers. The ability to predict the Tg value of a polymer preceding its synthesis is of enormous value. For this reason it is of great value to perform a predictive quantitative structure–property relationships analysis of Tg, in this case a new set of halogenated polymers was used for this purpose. In addition, to corroborate our previous findings, the best way to encode the polymers structure for this type of studies was further tested finding that the optimal option is once more to use three monomeric units. The best linear model constructed from 153 molecular structures incorporated seven molecular descriptors and showed excellent predictive ability. Furthermore, the method showed to be very simple and straightforward for the prediction of Tg since three-dimensional descriptors are not required.

Natural Acylated Anthocyanins and Other Related Flavonoids: Structure Elucidation of Ipomoea cairica Compounds and QSAR Studies Including Multidrug Resistance

Abstract Structure elucidation of new acylated anthocyanins is a challenging task because of molecule complexity, sensitivity to light, atmospheric oxygen, pH, and temperature. The type, number, and position of the acyl moieties should be carefully assessed. New anthocyanins acylated with cinnamic acid derivatives attached to the disaccharide sophorose have been recently isolated, purified, and completely identified in our research group. Structure determination was performed by chemical methods, and spectroscopic techniques, including 1 H and 13 C NMR, 2D NMR, and MS. Connection relationships between an aglycone moiety, three sugars, and one and two acyl groups, respectively, for each compound were also confirmed by HMBC and NOESY measurements. Therefore, six structures of cyanidin sophorosides acylated with caffeoyl and p -coumaroyl residues, isolated from Ipomoea cairica (family: Convolvulaceae), were fully elucidated. These acylated anthocyanins showed antioxidant activity and antimutagenicity. Quantitative structure–activity relationship studies of flavonoids and biflavonoids as enzyme inhibitors are discussed, e.g., inhibiting influenza H1N1 virus neuraminidase, and as inhibitors of P-glycoprotein in multidrug resistance.