In silico attempt for adduct agent(s) against malaria: Combination of chloroquine with alkaloids of Adhatoda vasica

Promoter sequence interaction and structure based multi-targeted (redox regulatory genes) molecular docking analysis of vitamin E and curcumin in T4 induced oxidative stress model using H9C2 cardiac cell line

A positive association between oxidative stress and hyper-thyroid conditions is well established. Vitamin E (VIT-E) and curcumin (CRM) are considered as potent antioxidant small molecules. Nuclear factor erythroid 2-related factor 2(NRF-2) is known to bind with antioxidant response element and subsequently activate expression of antioxidant enzymes. However, the activation of NRF-2 depends on removal of its regulator Kelch-like ECH-associated protein 1(NRF-2). In the current study, an attempt is made to demonstrate whether effects of VIT-E and CRM are due to direct interaction with the target proteins (i.e. NRF-2, NRF-2, SOD, catalase and LDH) or by possible interaction with the flanking region of their promoters by in silico analysis. Further, these results were corroborated by pretreatment of H9C2 cells (1 x 10⁶ cells per mL of media) with VIT-E (50 μM) and/or CRM (20 μM) for 24 h followed by induction of oxidative stress via T4 (100 nm) administration and assaying the active oxygen metabolism. Discriminant function analyses (DFA) indicated that T4 has a definite role in increasing oxidative stress as evidenced by induction of ROS generation, increase in mitochondrial membrane potential and elevated lipid peroxidation (LPx). Pretreatment with the two antioxidants have ameliorative effects more so when given in combination. The decline in biological activities of the principal antioxidant enzymes SOD and CAT with respect to T4 treatment and its restoration in antioxidant pretreated group further validated our in silico data. Communicated by Ramaswamy H. Sarma.

Recent Advances in the Development of Triose Phosphate Isomerase Inhibitors as Antiprotozoal Agents

BACKGROUND

Parasitic diseases caused by protozoa such as Chagas disease, leishmaniasis, malaria, African trypanosomiasis, amebiasis, trichomoniasis, and giardiasis are considered serious public health problems in developing countries. Drug-resistance among parasites justifies the search for new therapeutic drugs and the identification of new targets becomes a valuable approach. In this scenario, glycolysis pathway which consists of the conversion of glucose into pyruvate plays an important role in the protozoa energy supply and it is therefore considered as a promising target. In this pathway, triose phosphate isomerase (TIM) plays an essential role in efficient energy production. Furthermore, protozoa TIM show structural differences with human enzyme counterparts suggesting the possibility of obtaining selective inhibitors. Therefore, TIM is considered a valid approach to develop new antiprotozoal agents, inhibiting the glycolysis in the parasite.

OBJECTIVE

In this review, we discuss the drug design strategies, structure-activity relationship, and binding modes of outstanding TIM inhibitors against Trypanosoma cruzi, Trypanosoma brucei, Plasmodium falciparum, Giardia lamblia, Leishmania mexicana, Trichomonas vaginalis, and Entamoeba histolytica.

RESULTS

TIM inhibitors showed mainly aromatic systems and symmetrical structure, where the size and type of heteroatom are important for enzyme inhibition. This inhibition is mainly based on the interaction with i) the interfacial region of TIM inducing changes on the quaternary and tertiary structure or ii) with the TIM catalytic region were the main pathways that disabled the catalytic activity of the enzyme.

CONCLUSION

Benzothiazole, benzoxazole, benzimidazole, and sulfhydryl derivatives stand out as TIM inhibitors. In silico and in vitro studies demonstrate that the inhibitors bind mainly at the TIM dimer interface. In this review, the development of new TIM inhibitors as antiprotozoal drugs is demonstrated as an important pharmaceutical strategy that may lead to new therapies for these ancient parasitic diseases.

Possible activation of NRF2 by Vitamin E/Curcumin against altered thyroid hormone induced oxidative stress via NFĸB/AKT/mTOR/KEAP1 signalling in rat heart

Oxidative stress is implicated in both hypo- and hyper-thyroid conditions. In the present study an attempt has been made to elucidate possible interaction between vitamin E or/and curcumin (two established antioxidants) with active portion (redox signaling intervening region) of nuclear factor erythroid 2-related factor 2 (NRF2) as a mechanism to alleviate oxidative stress in rat heart under altered thyroid states. Fifty Wistar strain rats were divided into two clusters (Cluster A: hypothyroidism; Cluster B: hyperthyroidism). The hypo- (0.05% (w/v) propylthiouracil in drinking water) and hyper- (0.0012% (w/v) T4 in drinking water) thyroid rats in both clusters were supplemented orally with antioxidants (vitamin E or/and curcumin) for 30 days. Interactive least count difference and principal component analyses indicated increase in lipid peroxidation, reduced glutathione level, alteration in the activities and protein expression of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase under altered thyroid states. However, the expression of stress survival molecules; nuclear factor κB (NFκB) and the serine-threonine kinase B (Akt), in hyper-thyroidism only points towards different mechanisms responsible for either condition. Co-administration of vitamin E and curcumin showed better result in attenuating expression of mammalian target for rapamycin (mTOR), restoration of total protein content and biological activity of Ca²⁺ ATPase in hyperthyroid rats, whereas, their individual treatment showed partial restoration. Since NRF2 is responsible for activation of antioxidant response element and subsequent expression of antioxidant enzymes, possible interactions of both vitamin E or/and curcumin with the antioxidant enzymes, NRF2 and its regulator Kelch ECH associating protein (KEAP1) were studied in silico. For the first time, a modeled active portion of the zipped protein NRF2 indicated its interaction with both vitamin E and curcumin. Further, curcumin and vitamin E complex showed in silico interaction with KEAP1. Reduction of oxidative stress by curcumin and/or vitamin E may be due to modulation of NRF2 and KEAP1 function in rat heart under altered thyroid states.

A systematic and prospectively validated approach for identifying synergistic drug combinations against malaria

Background

Nearly half of the world’s population (3.2 billion people) were at risk of malaria in 2015, and resistance to current therapies is a major concern. While the standard of care includes drug combinations, there is a pressing need to identify new combinations that can bypass current resistance mechanisms. In the work presented here, a combined transcriptional drug repositioning/discovery and machine learning approach is proposed.

Methods

The integrated approach utilizes gene expression data from patient-derived samples, in combination with large-scale anti-malarial combination screening data, to predict synergistic compound combinations for three Plasmodium falciparum strains (3D7, DD2 and HB3). Both single compounds and combinations predicted to be active were prospectively tested in experiment.

Results

One of the predicted single agents, apicidin, was active with the AC50 values of 74.9, 84.1 and 74.9 nM in 3D7, DD2 and HB3 P. falciparum strains while its maximal safe plasma concentration in human is 547.6 ± 136.6 nM. Apicidin at the safe dose of 500 nM kills on average 97% of the parasite. The synergy prediction algorithm exhibited overall precision and recall of 83.5 and 65.1% for mild-to-strong, 48.8 and 75.5% for moderate-to-strong and 12.0 and 62.7% for strong synergies. Some of the prospectively predicted combinations, such as tacrolimus-hydroxyzine and raloxifene-thioridazine, exhibited significant synergy across the three P. falciparum strains included in the study.

Conclusions

Systematic approaches can play an important role in accelerating discovering novel combinational therapies for malaria as it enables selecting novel synergistic compound pairs in a more informed and cost-effective manner.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2294-5) contains supplementary material, which is available to authorized users.

Antibacterial, antifungal and antimycobacterial compounds from cyanobacteria

Infections from multidrug resistant (MDR) pathogenic bacteria, fungi and Mycobacterium tuberculosis remain progressively intractable. The search of effective antimicrobials from other possible non-conventional sources against MDR pathogenic bacteria, fungi and mycobacteria is call of the day. This review considers 121 cyanobacterial compounds or cyano-compounds with antimicrobial activities. Chemical structures of cyano-compounds were retrieved from ChemSpider and PubChem databases and were visualized by the software ChemDraw Ultra. Chemical information on cyano-compounds pertaining to Lipinski rules of five was assessed. The reviewed cyano-compounds belong to the following chemical classes (with examples): alkaloids (ambiguine isonitriles and 12-epi-hapalindole E isonitrile), aromatic compounds (benzoic acid and cyanobacterin), cyclic depsipeptides (cryptophycin 52 and lyngbyabellin A), cyclic peptides (calophycin and tenuecyclamides), cyclic undecapeptides (kawaguchipeptins and lyngbyazothrin A), cyclophane (carbamidocyclophane), extracellular pigment (nostocine A), fatty acids (alpha-dimorphecolic acid and majusculonic acid), linear peptides (muscoride A), lipopeptides (fischerellins and scytonemin A), nucleosides (tolytoxin and tubercidin), phenols (ambigols and 4-4'-hydroxybiphenyl), macrolides (scytophycin A and tolytoxin), polyketides (malyngolide and nostocyclyne), polyphenyl ethers (crossbyanol A), porphinoids (tolyporphin J) and terpenoids (noscomin and scytoscalarol). Cyanobacteria appear to be a diverse source of compounds with antimicrobial activity. Further attention is required to elucidate whether those could be applied as pharmaceuticals.

Development of antibacterial conjugates using sulfamethoxazole with monocyclic terpenes: A systematic medicinal chemistry based computational approach

BACKGROUND AND OBJECTIVE

To develop 6 conjugate agents of the moribund antibiotic sulfamethoxazole (SMZ) joined to 6 individual monoterpenes, followed by protocols of medicinal chemistry as potent antibacterials, against multidrug resistant (MDR) human gruesome pathogenic bacteria.

METHODS

Antibacterial activities of the proposed conjugates were ascertained by the 'prediction of activity spectra of substances' (PASS) program. Drug-likeness parameters and toxicity profiles of conjugates were standardized with the Lipinski rule of five, using cheminformatic tools, Molsoft, molinspiration, OSIRIS and ProTox. Antibacterial activities of individual chemicals and conjugates were examined by targeting the bacterial folic acid biosynthesis enzyme, dihydropteroate synthases (DHPSs) of bacteria, Bacillus anthracis, Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae and Mycobacterium tuberculosis, with 3D structures of DHPSs from protein data bank.

RESULTS

According to the PASS program, biological spectral values of conjugate-2, conjugate-5 and conjugate-6 were ascertained effective with 'probably active' or 'Pa' value > 0.5, for anti-infective and antituberculosic activities. Using molecular docking against 5 cited bacterial DHPSs, effective docking scores of 6 monoterpenes in the specified decreasing order (kcal/mol): -9.72 (eugenol against B. anthracis), -9.61 (eugenol against S. pneumoniae), -9. 42 (safrol, against B. anthracis), -9.39 (thymol, against M. tuberculosis), -9.34 (myristicin, against S. pneumoniae) and -9.29 (thymol, against B. anthracis); whereas the lowest docking score of SMZ was -8.46kcal/mol against S. aureus DHPS. Similarly, effective docking scores of conjugates were as specified (kcal/mol.): -10.80 (conjugate-4 consisting SMZ+safrol, against M. tuberculosis), -10.78 (conjugate-5 consisting SMZ+thymol, against M. tuberculosis), -10.60 (conjugate-5 against B. anthracis), -10.26 (conjugate-2 consisting SMZ+ eugenol, against M. tuberculosis), -10.25 (conjugate-5, against S. aureus) and -10.19 (conjugate-2 against S. pneumoniae. Conjugates-2 and -5 were the most effective antibacterials based on Lipinski rule of five with lethal doses 3471 and 3500mg/kg, respectively and toxicity class levels.

CONCLUSIONS

Conjugate-2 and conjugate-5 were more effective than individual monoterpenes and SMZ, against pathogenic bacteria. Synthesis, characterization and in vitro antibacterial study with acute toxicity testing for Wister rat model of the conjugate-5 could land at success in the recorded computational trial and it could be promoted for synthesis in the control of MDR bacteria.