Virtual screening of natural products inspired in-house library to discover potential lead molecules against the SARS-CoV-2 main protease.

SARS-CoV-2, a new coronavirus emerged in 2019, causing a global healthcare epidemic. Although a variety of drug targets have been identified as potential antiviral therapies, and effective candidate against SARS-CoV-2 remains elusive. One of the most promising targets for combating COVID-19 is SARS-CoV-2 Main protease (Mpro, a protein responsible for viral replication. In this work, an in-house curated library was thoroughly evaluated for druggability against Mpro. We identified four ligands (FG, Q5, P5, and PJ4) as potential inhibitors based on docking scores, predicted binding energies (MMGBSA), in silico ADME, and RMSD trajectory analysis. Among the selected ligands, FG, a natural product from Andrographis nallamalayana, exhibited the highest binding energy of -10.31 kcal/mol close to the docking score of clinical candidates Boceprevir and GC376. Other ligands (P5, natural product from cardiospermum halicacabum and two synthetic molecules Q5 and PJ4) have shown comparable docking scores ranging -7.65 kcal/mol to -7.18 kcal/mol. Interestingly, we found all four top ligands had Pi bond interaction with the main amino acid residues HIS41 and CYS145 (catalytic dyad), H-bonding interactions with GLU166, ARG188, and GLN189, and hydrophobic interactions with MET49 and MET165 in the binding site of Mpro. According to the ADME analysis, Q5 and P5 are within the acceptable range of drug likeliness, compared to FG and PJ4. The interaction stability of the lead molecules with viral protease was verified using replicated MD simulations. Thus, the present study opens up the opportunity of developing drug candidates targeting SARS-CoV-2 main protease (Mpro) to mitigate the disease.Communicated by Ramaswamy H. Sarma.

Catecholase-catalyzed synthesis of wedelolactone, a natural coumestan and its analogs.

Biocatalysis plays an important role in the synthesis of complex organic molecules. Wedelolactone, a natural coumestan, has been reported to have many bioactive properties. A novel and efficient enzyme obtained from sweet potato juice was used for condensation of 4-hydroxycoumarins with catechols to produce wedelolactone and its structurally diverse analogs in moderate to good yields under mild reaction conditions. Hence, this enzymatic approach creates an opportunity to access many coumestan-based compounds that are potential building blocks for the synthesis of pharmaceutically important molecules.

Furan derivatives impair proliferation and affect ultrastructural organization of Trypanosoma cruzi and Leishmania amazonensis.

Chagas disease and leishmaniasis are neglected diseases caused by parasites of the Trypanosomatidae family and together they affect millions of people in the five continents. The treatment of Chagas disease is based on benznidazole, whereas for leishmaniasis few drugs are available, such as amphotericin B and miltefosine. In both cases, the current treatment is not entirely efficient due to toxicity or side effects. Encouraged by the need to discover valid targets and new treatment options, we evaluated 8 furan compounds against Trypanosoma cruzi and Leishmania amazonensis, considering their effects against proliferation, infection, and ultrastructure. Many of them were able to impair T. cruzi and L. amazonensis proliferation, as well as cause ultrastructural alterations, such as Golgi apparatus disorganization, autophagosome formation, and mitochondrial swelling. Taken together, the results obtained so far make these compounds eligible for further steps of chemotherapy study.

A bis-indole/carbazole based C5-curcuminoid fluorescent probe with large Stokes shift for selective detection of biothiols and application to live cell imaging.

A series of heterocyclic C5-curcuminoids (bis(arylmethylidene)acetones) (PJ1-PJ6) having a large Stokes shift (Δλ = 104-173 nm) have been synthesized for the selective detection of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in living cells. The compounds were synthesized using a new methodology via deacetylation under microwave conditions. The photophysical properties of these compounds have been studied. Prominent colour changes from bright yellow to colourless in the presence of thiols were observed for PJ1. Live cell imaging has been employed with PJ1 for the utilization of the probe to detect homocysteine in A375 cells and apoptosis in AGS cells.

Establishment of atropisomerism in 3-indolyl furanoids: a synthetic, experimental and theoretical perspective.

Introduction of axial chirality in bioactive 3-indolyl furanoids has been achieved by systematic alteration of functional groups around the stereogenic axis, keeping in mind that atropisomerically pure analogues may possess different binding affinities and selectivities towards a target protein. The kinetics of racemization of axially chiral 3-indolyl furanoids have been studied through chiral HPLC analysis, electronic circular dichroism (ECD) spectroscopy, and computational modeling. The results identify the configurational parameters for optically pure 3-indolyl furanoids to exist as stable and isolable atropisomeric form.

Fiaud's Acid: A Brønsted Acid Catalyst for Enantioselective Friedel-Crafts Alkylation of Indoles with 2-Alkene-1,4-diones.

Fiaud's acid (trans-1-hydroxy-2,5-diphenylphospholane 1-oxide), a phospholane-based phosphinic acid, is introduced as an efficient chiral Brønsted acid catalyst that mediates the asymmetric Friedel-Crafts alkylation of indoles with 2-butene-1,4-diones. With a catalyst loading of 10 mol %, the reaction proceeded smoothly to afford 2-(indol-3-yl)butane-1,4-diones in high yield (up to 82%) and high enantioselectivity (up to 91% ee, one such product showed enhanced ee of 98% after recrystallization). The reaction conditions are sufficiently mild to tolerate sensitive functionality at room temperature and are therefore suitable for the synthesis of complex targets.

Substituted furans as potent lipoxygenase inhibitors: Synthesis, in vitro and molecular docking studies.

A number of 2-methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-furan-3-carboxylic acid alkyl ester derivatives (3a-j) were synthesized and evaluated for their in vitro inhibitory activity on soybean lipoxygenase enzyme. Among the screened compounds, 5-(4-bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-ethyl]-2-methyl-furan-3-carboxylic acid methyl ester (3g) has been found to exhibit potent inhibitory activity with IC5012.8µM using nordihydroguaiaretic acid (NDGA) as standard. Molecular modeling was employed for better understanding of the binding between compounds and soybean lipoxygenase enzyme. The predicted binding energy values correlated well with the observed in vitro data.