Sanjukta Patra

Rational approaches for drug designing against leishmaniasis.

Leishmaniasis has been ignored for many years mainly because it plagues remote and poor areas. However, recently, it has drawn attention of several investigators, and active research is going on for antileishmanial drug discovery. The current available drugs have high failure rates and significant side effects. Recently, liposomal preparations of amphotericin B are available and have proved to be a better drug, but they are very expensive. Miltefosine is one of the few orally administered drugs that are effective against Leishmania. However, it has exhibited teratogenicity, hence, should not be administered to pregnant women. Thus, the search for novel and improved antileishmanial drugs continue. A rational approach to design and develop new antileishmanials can be to identify several metabolic and biochemical differences between host and parasite that can be exploited as drug target. Moreover, many natural products also have significant antileishmanial activity and are yet to be exploited. In the current review, we aim to bring together various drug targets of Leishmania, recent development in the field, future prospects, and hope in the area.

Potential Biomarkers and Their Applications for Rapid and Reliable Detection of Malaria

Malaria has been responsible for the highest mortality in most malaria endemic countries. Even after decades of malaria control campaigns, it still persists as a disease of high mortality due to improper diagnosis and rapidly evolving drug resistant malarial parasites. For efficient and economical malaria management, WHO recommends that all malaria suspected patients should receive proper diagnosis before administering drugs. It is thus imperative to develop fast, economical, and accurate techniques for diagnosis of malaria. In this regard an in-depth knowledge on malaria biomarkers is important to identify an appropriate biorecognition element and utilize it prudently to develop a reliable detection technique for diagnosis of the disease. Among the various biomarkers, plasmodial lactate dehydrogenase and histidine-rich protein II (HRP II) have received increasing attention for developing rapid and reliable detection techniques for malaria. The widely used rapid detection tests (RDTs) for malaria succumb to many drawbacks which promotes exploration of more efficient economical detection techniques. This paper provides an overview on the current status of malaria biomarkers, along with their potential utilization for developing different malaria diagnostic techniques and advanced biosensors.

Iridoid glucosides from Nyctanthes arbortristis result in increased reactive oxygen species and cellular redox homeostasis imbalance in Leishmania parasite

We report here the effect of iridoid glucosides, isolated from Nyctanthes arbortristis, on redox homeostasis of Leishmania parasite. These compounds led to an increase in reactive oxygen species by inhibiting a crucial enzyme of redox metabolism of the parasite. Our experiments clearly showed that these compounds are highly active as antileishmanial agents. The in vitro experiments on intra-macrophageal amastigotes showed significant killing of parasite even at very low concentration. Determination of mechanism of action of iridoid glucosides showed that increased ROS level leads to oxidative stress, cell membrane damage and apoptosis of Leishmania sp. Our cellular toxicity assays on Human embryonic kidney (HEK 293) and mouse macrophage (J774A.1) cell lines showed these compounds to be very safe for therapeutics application.

Evaluation of selected antitumor agents as subversive substrate and potential inhibitor of trypanothione reductase: an alternative approach for chemotherapy of Leishmaniasis

Trypanothione reductase (TryR) is a validated drug target against Leishmaniasis. Using integrated computational and experimental approaches, the authors report doxorubicin and mitomycin C, known antitumor agents, as novel inhibitors of TryR of leishmania parasite. Interestingly, these compounds also act as subversive substrates and subvert the physiological function of enzyme by converting it from an anti-oxidant to a pro-oxidant. Possible mechanism of subversive substrate is discussed. Both doxorubicin and mitomycin C show significant effect on redox homeostasis of the parasite and high-leishmanicidal activity. The toxicity studies as well as available toxicity data in literature indicate these compounds to have acceptable toxicity in limited dose.

Unraveling the rationale behind organic solvent stability of lipases.

Organic solvent-stable lipases have pronounced impact on industrial economy as they are involved in synthesis by esterification, interesterification, and transesterification. However, very few of such natural lipases have been isolated till date. A study of the recent past provided few pillars to rely on for this work. The three-dimensional structure, inclusive of the surface and active site, of 29 organic solvent-stable lipases was analyzed by subfamily classification and protein solvent molecular docking based on fast Fourier transform correlation approach. The observations revealed that organic solvent stability of lipases is their intrinsic property and unique with respect to each lipase. In this paper, factors like surface distribution of charged, hydrophobic, and neutral residues, interaction of solvents with catalytically immutable residues, and residues interacting with essential water molecules required for lipase activity, synergistically and by mutualism contribute to render a stable lipase organic solvent. The propensity of surface charge in relation to stability in organic solvents by establishing repulsive forces to exclude solvent molecules from interacting with the surface and prohibiting the same from gaining entry to the protein core, thus stabilizing the active conformation, is a new finding. It was also interesting to note that lipases having equivalent surface-exposed positive and negative residues were stable in a wide range of organic solvents, irrespective of their LogP values.

Deciphering molecular mechanism underlying antileishmanial activity of Nyctanthes arbortristis, an Indian medicinal plant

ETHNOPHARMACOLOGICAL RELEVANCE Nyctanthes arbortristis L. (Oleaceae) is widely used in the traditional medicine of India. The plant is shown to have antibacterial and antileishmanial activities. AIM OF THE STUDY Evaluation of iridoid glucosides from the plant as inhibitor of trypanothione reductase (TryR), a validated drug target enzyme of the Leishmania parasite. The study contributes towards understanding mechanism of antileishmanial effect of the plant. MATERIALS AND METHODS TryR of Leishmania parasite is expressed and purified. Iridoid glucosides are isolated from the plant and tested as inhibitor of TryR enzyme of the parasite. RESULTS Inhibitory constant (K(i)) of various iridoid glucosides ranges from 3.24±0.05 μM to 6.49±0.05 μM. Thus, the molecular mechanism underlying antileishmanial activity of these compounds is mediated through inhibition of TryR. CONCLUSION The current study also points out towards potential application of iridoid glucosides as novel drugs against the disease.

An insight into plant lipase research - challenges encountered.

Lipases from bacterial, fungal, and animal sources have been purified to homogeneity with very few of them being contributed from plants. Plant lipases are mostly found in energy reserve tissues, for example, oilseeds. They act as biocatalysts which are attractive due to their high substrate specificity, low production cost and easy pharmacological acceptance due to their eukaryotic origin. Hence plant lipases represent better potential for commercial applications in organic synthesis, food, detergent and pharmacological industries. However, low expression, uneconomical fold purity and the plethora of difficulties related to their recombinant expression has been limiting their commercial applicability and posing challenges to many researchers. This article focuses on comprehensive approaches that have been reported to date to address these challenges.

In silico characterization of thermostable lipases

Thermostable lipases are of high priority for industrial applications as they are endowed with the capability of carrying out diversified reactions at elevated temperatures. Extremophiles are their potential source. Sequence and structure annotation of thermostable lipases can elucidate evolution of lipases from their mesophilic counterparts with enhanced thermostability hence better industrial potential. Sequence analysis highlighted the conserved residues in bacterial and fungal thermostable lipases. Higher frequency of AXXXA motif and poly Ala residues in lid domain of thermostable Bacillus lipases were distinguishing characteristics. Comparison of amino acid composition among thermostable and mesostable lipases brought into light the role of neutral, charged and aromatic amino acid residues in enhancement of thermostability. Structural annotation of thermostable lipases with that of mesostable lipases revealed some striking features which are increment of gamma turns in thermostable lipases; being first time reported in our paper, longer beta strands, lesser beta-branched residues in helices, increase in charged-neutral hydrogen bonding pair, hydrophobic-hydrophobic contact and differences in the N-cap and C-cap residues of the α helices. Conclusively, it can be stated that subtle changes in the arrangement of amino acid residues in the tertiary structure of lipases contributes to enhanced thermostability.

Gold nanoparticles based colorimetric aptasensor for theophylline

A simple colorimetric aptasensor for the detection of theophylline was investigated using stable RNA aptamer and gold nanoparticles (AuNPs). Theophylline, a purine derivative, structurally similar to caffeine is broadly used in the treatment of respiratory diseases and bronchial asthma. A highly stable RNA aptamer that selectively binds to the theophylline molecule was prepared by structural modification of the 2′-hydroxyl group of ribose to 2′-fluoro (5′GGC GAU ACC AGC CGA AAA GGC CCU UGG CAG CGU C3′) in all the pyrimidines in a 34-mer length aptamer. The RNA aptamer binds to AuNPs by simple electrostatic interactions thereby inhibiting salt induced aggregation. AuNPs are aggregated due to detachment of the theophylline specific RNA aptamer from the surface of the AuNPs as a result of interaction with the target leading to a color change from red to purple. By successfully optimizing the concentration of aptamer, AuNPs, salts and stability of the aptamer, a detection limit of 50 ng mL−1 theophylline was achieved. Analyses of theophylline in samples were carried out, and the observed recovery was 97–98.7% with a relative standard deviation in the range of 2.69–19.4%. The results obtained were compared with those of an HPLC method. This colorimetric aptasensor is advantageous for onsite visual detection.

Mitogen-activated protein kinase 4 of Leishmania parasite as a therapeutic target.

Protein kinases are important regulators of many different cellular processes such as transcriptional control, cell cycle progression and differentiation, and have drawn much attention as potential drug targets. Leishmania mexicana mitogen-activated protein kinase 4 (LmxMPK4) is crucial for the survival of the parasite. As the crystal structure of the enzyme is not known, we have used bioinformatics techniques to model LmxMPK4 structure. The current study reveals conservation of all sequence and structural motifs of LmxMPK4. Study shows mitogen-activated protein kinases are highly conserved throughout different Leishmania species and significant divergence is observed towards mammalian mitogen-activated protein kinases. Additionally, using virtual docking methods, we have identified inhibitors for LmxMPK4. The sequence and structure analysis results were helpful in identifying the ligand binding sites and molecular function of the Leishmania specific mitogen-activated protein kinase.