Synthesis, molecular modelling studies of indolyl chalcone derivatives and their antimalarial activity evaluation.

Twenty one chalcone derivatives were synthesized using Claisen-Schmidt condensation, their antimalarial activity against Plasmodium falciparum was determined and quantitative structure-activity relationship (QSAR) was developed. Condensation of substituted acetophenones with various aromatic aldehydes at room temperature gave chalcones in 75-96% yield. Chalcones are secondary metabolites of terrestrial plants, precursors for the biosynthesis of flavonoids and exhibit various biological activities. Antiplasmodial IC50 (half-maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was Trans-3-(1H-indol-3-yl)-1-(2'-hydroxyphenyl)-2-propen-1-one (1b) with IC50 of 2.1 µM/L. Molecular mechanism was explored through in silico docking & ADMET studies for the active compounds.

In vitro antiproliferative activity of glabridin derivatives and their in silico target identification.

Novel Mannich base derivatives of glabridin were synthesized and their antiproliferative activity were performed along with our previously reported glabridin-chalcone hybrids molecules (GCHMs) against various human cell lines MDA-MB-231 (breast adenocarcinoma), HEK-293 (embryonic kidney cell line), K562 (leukemia), MCF-7 (breast adenocarcinoma), HeLa (cervix adenocarcinoma), HepG2 (hepatocellular carcinoma) and WRL-68 (hepatic carcinoma). The result showed that the glabridin significantly reduced cell proliferation with IC50 ranges from 3.67 to 58.30 µM against all the tested cell lines. The remarkable reduction in antiproliferative activity 2',4'-dimethoxyglabridin and GCHMs compounds with phenolic OH groups protected by methoxy (OCH3) groups suggested that the free OH groups are essential factor for the antiproliferative activity of glabridin and its derivatives. The Mannich base derivatives of glabridin showed moderate activity IC50 (2.20->95.78 µM). Furthermore, in silico target identification analysis revealed that AKT1, DECR1 and NOS1 are the potential targets for glabridin and their derivatives.

A novel bi-functional chalcone inhibits multi-drug resistant Staphylococcus aureus and potentiates the activity of fluoroquinolones.

Staphylococcus aureus is the leading cause of bacteraemia and the dwindling supply of effective antibacterials has exacerbated the problem of managing infections caused by this bacterium. Isoliquiritigenin (ISL) is a plant flavonoid that displays therapeutic potential against S. aureus. The present study identified a novel mannich base derivatives of ISL, IMRG4, active against Vancomycin intermediate S. aureus (VISA). IMRG4 damages the bacterial membranes causing membrane depolarization and permeabilization, as determined by loss of salt tolerance, flow cytometric analysis, propidium idodie and fluorescent microscopy. It reduces the intracellular invasion of HEK-293 cells by S. aureus and decreases the staphylococcal load in different organs of infected mice models. In addition to anti-staphylococcal activity, IMRG4 inhibits the multidrug efflux pump, NorA, which was determined by molecular docking and EtBr efflux assays. In combination, IMRG4 significantly reduces the MIC of norfloxacin for clinical strains of S. aureus including VISA. Development of resistance against IMRG4 alone and in combination with norfloxacin was low and IMRG4 prolongs the post-antibiotic effect of norfloxacin. These virtues combined with the low toxicity of IMRG4, assessed by MTT assay and haemolysis, makes it an ideal candidate to enter drug development pipeline against S. aureus.

Synthesis of a series of novel dihydroartemisinin monomers and dimers containing chalcone as a linker and their anticancer activity.

A new series of monomer and dimer derivatives of dihydroartemisinin (DHA) containing substituted chalcones as a linker were synthesized and investigated for their cytotoxicity in human cancer cell lines HL-60 (leukemia), Mia PaCa-2 (pancreatic cancer), PC-3 (prostate cancer), LS180 (colon cancer) and HEPG2 (hepatocellular carcinoma). Some of these derivatives have greater antiproliferative and cytotoxic effects in tested cell lines than parent compound DHA. The structures of the all compounds were confirmed by IR, (1)H NMR and mass spectral data. Among the new derivatives, compounds 8, 14, 15, 20 and 24 were found to be more active than parent DHA against tested human cancer cell lines. DHA derivatives were found to be most active in human leukemia cell lines with compounds 8, 14, 15, 20 and 24 showed IC50 values less than 1 µM for 48 h whereas DHA has IC50 value of 2 µM at same time period. The most potent compounds 8 with IC50 = 0.3 µM (at par with doxorubicin (IC50 = 0.3 µM)) and 15 with IC50 = 0.4 µM, of the series, six and three times active than DHA (with IC50 = 2 µM) respectively were selected for further mechanistic work in human leukemia HL-60 cells.

Drug Resistance Reversal Potential of Isoliquiritigenin and Liquiritigenin Isolated from Glycyrrhiza glabra Against Methicillin-Resistant Staphylococcus aureus (MRSA).

Isoliquiritigenin (ISL) and liquiritigenin (LTG) are structurally related flavonoids found in a variety of plants. Discovery of novel antimicrobial combinations for combating methicillin-resistant Staphylococcus aureus (MRSA) infections is of vital importance in the post-antibiotic era. The present study was taken to explore the in vitro and in vivo combination effect of LTG and ISL with ß-lactam antibiotics (penicillin, ampicillin and oxacillin) against mec A-containing strains of MRSA. Minimum inhibitory concentration (MIC) of both LTG and ISL exhibited significant anti-MRSA activity (50-100 µg/mL) against clinical isolates of MRSA. The result of in vitro combination study showed that ISL significantly reduced MIC of ß-lactam antibiotics up to 16-folds [∑ fractional inhibitory concentration (FIC) 0.312-0.5], while LTG reduced up to 8-folds (∑FIC 0.372-0.5). Time kill kinetics at graded MIC combinations (ISL/LTG + ß-lactam) indicated 3.27-9.79-fold and 2.59-3.48-fold reduction in the growth of clinical isolates of S. aureus respectively. In S. aureus-infected Swiss albino mice model, combination of ISL with oxacillin significantly (p < 0.05, p < 0.01, p < 0.001) lowered the systemic microbial burden in blood, liver, kidney, lung and spleen tissues in comparison with ISL, oxacillin alone as well as untreated control. Considering its synergistic antibacterial effect, we suggest both ISL and LTG as promising compounds for the development of novel antistaphylococcal combinations. Copyright © 2016 John Wiley & Sons, Ltd.

Molecular modeling based synthesis and evaluation of in vitro anticancer activity of indolyl chalcones.

A series of twenty one chalcone derivatives having indole moiety were synthesized and were evaluated against four human cancer cell lines. Indolyl chalcones 1a, 1b, 1d, 1f-1j, 2c, 2e, 2i showed good anticancer activity. Chalcones 1b and 1d were the most active and selective anticancer agents with IC50 values <1µg/ml and 1.51µg/ml, against WRL-68 cell line, respectively. Molecular mechanism was explored through in silico docking & ADMET studies.

Molecular modeling based semi-synthesis and in vitro evaluation of anticancer activity in indolyl chalcones.

A series of indolyl chalcones were synthesized and evaluated in vitro for their anticancer activity against four human cancer cell lines. Compounds 1a, 1b, 1d, 1f-1j, 2c, 2e, 2i showed significant cytotoxicity. Chalcones 1b and 1d were identified as the most potent and selective anticancer agents with IC50 values <1µg/ml and 1.51µg/ml, against WRL-68 cell line, respectively.

In vitro antimalarial studies of novel artemisinin biotransformed products and its derivatives.

Biotransformation of antimalarial drug artemisinin by fungi Rhizopus stolonifer afforded three sesquiterpenoid derivatives. The transformed products were 1α-hydroxyartemisinin (3), 3.0%, a new compound, 10ß-hydroxyartemisinin, 54.5% (4) and deoxyartemisinin (2) in 9% yield. The fungus expressed high-metabolism activity (66.5%). The chemical structures of the compounds were elucidated by 1D, 2D NMR spectrometry and mass spectral data. The major compound 10ß-hydroxyartemisinin (4) was chemically converted to five new derivatives 5-9. All the compounds 3-9 were subjected for in vitro anti-malarial activity. 10ß-Hydroxy-12ß-arteether (8), IC50 at 18.29nM was found to be 10 times better active than its precursor 4 (184.56nM) and equipotent antimalarial with natural drug artemisinin whereas the α-derivative 9 is 3 times better than 4 under in vitro conditions. Therefore, the major biotransformation product 4 can be exploited for further modification into new clinically potent molecules. The results show the versatility of microbial-catalyzed biotransformations leading to the introduction of a hydroxyl group at tertiary position in artemisinin in derivative (3).

QSAR and docking based semi-synthesis and in vivo evaluation of artemisinin derivatives for antimalarial activity.

To screen the active antimalarial novel artemisinin derivatives, a QSAR modeling approach was used. QSAR model showed high correlation (r(2)= 0.83 and rCV(2)= 0.81) and indicated that Connectivity Index (order 1, standard), Connectivity Index (order 2, standard), Dipole Moment (debye), Dipole Vector X (debye) and LUMO Energy (eV) well correlate with activity. High binding likeness on antimalarial target plasmepsin was detected through molecular docking. Active artemisinin derivatives showed significant activity and indicated compliance with standard parameters of oral bioavailability and ADMET. The active artemisinin derivatives namely, ß-Artecyclopropylmether HMCP (A3), ß- Artepipernoylether (PIP-1) (A4) and 9-(ß-Dihydroartemisinoxy)methyl anthracene (A5) were semi-synthesized and characterized based on its (1)H and (13)C NMR spectroscopic data and later activity tested in vivo on mice infected with multidrug resistant strain of P. yoelii nigeriensis. Predicted results were successfully validated by in vivo experiments.

In vivo anti-diabetic activity of derivatives of isoliquiritigenin and liquiritigenin.

Isoliquiritigenin (ISL), a chalcone and liquiritigenin (LTG), a flavonoid found in licorice roots and several other plants. ISL displays antioxidant, anti-inflammatory, antitumor and hepatoprotective activities whereas LTG is an estrogenic compound, acts as an agonist selective for the ß-subtype of the oestrogen receptor. Both the phenolics were isolated from the rhizomes of Glycyrrhiza glabra. Five derivatives from ISL and four derivatives from LTG were synthesized. All the compounds were established by extensive spectroscopic analyses and screened through oral glucose tolerance test to gain preliminary information regarding the antihyperglycemic effect in normal Swiss albino male mice. ISL (1), ISL derivatives 3, 4, 5, 7 and LTG derivatives 9 and 10 showed significant blood glucose lowering effect. The structure-activity relationship indicated that the presence of ether and ester groups in ISL and LTG analogues are important for exhibiting the activity. Compounds 1, 4 and 10 were selected for in vivo antidiabetic activity and found to be potential candidates for treatment of diabetes. It is the first report on antidiabetic activity of ISL derivative 4 and LTG derivative 10.

Antimalarial drug targets and drugs targeting dolichol metabolic pathway of Plasmodium falciparum.

Because of mutation and natural selection, development of drug resistance to the existing antimalarial is the major problem in malaria treatment. This problem has created an urgent need of novel antimalarial drug targets as well as lead compounds. The important characteristic of malaria is that it shows the phenomenon of balanced polymorphisms. Several traits have been selected in response to disease pressure. Therefore such factors must be explored to understand the pathogenesis of malaria infection in human host. Apicoplast, hub of metabolism is present in Plasmodium falciparum (causative agent of falciparum malaria) having similarities with plant plastid. Among several pathways in apicoplast, Dolichol metabolic pathway is one of the most important pathway and has been known to play role in parasite survival in the human host. In P.falciparum, a phosphorylated derivative of Dolichol participates in biosynthesis of glycoproteins. Several proteins of this pathway play role in post translational modifications of proteins involved in the signal transduction pathways, regulation of DNA replication and cell cycle. This pathway can be used as antimalarial drug target. This report has explored progress towards the study of proteins and inhibitors of Dolichol metabolic pathway. For more comprehensive analysis, the host genetic factors and drug-protein interaction have been covered.

Antiplasmodial activity of artecyclopentyl mether a new artemisinin derivative and its effect on pathogenesis in Plasmodium yoelii nigeriensis infected mice.

In an effort to evaluate novel derivatives from artemisinin, possessing potential antimalarial activity, a new derivative artecyclopentyl mether (CPM-1) was derivatized and evaluated for its dose-dependent efficacy in Plasmodium yoelii nigeriensis infected mice. The survivability of mice at 7.5 mg/kg was >28 days with negligible parasitaemia and recovered anemia (66.16-72.62%). Artecyclopentyl mether was also found to modulate the pro- and anti-inflammatory cytokines (IFN-γ, 39.64-56.92%; TNF, 49.10-74.31%; IL-4, 11.53-43.22%; IL-10, 37.60-53.52%) favourably besides optimizing the oxidative stress to the infected subjects as evident by the nitric oxide (88.76-95.43%), lipid peroxidation (59.30-76.05%) and glycaemic data (62.70-76.66%). The results indicate the potentiality of the new derivative as an antimalarial against asexual stages of the parasite.

Liquiritigenin derivatives and their hepatotoprotective activity.

Liquiritigenin (7,4'-dihydroxyflavanone), isolated from the roots of Glycyrrhiza glabra, was derivatized to liquiritigenin 7, 4'-diacetate, liquiritigenin 4'-acetate, isoliquiritigenin, and liquiritigenin 7, 4'-dibenzoate. All these derivatives were evaluated for in vitro hepatoprotective activity against D-galactosamine-lipopolysaccharide(GalN/LPS) induced toxicity. In-vitro hepatotoxicity was manifested by a significant increase (P < 0.05) in liver toxicity biomarkers (SGPT, SGOT, ALKP, triglyceride, LPO, NO and LDH). The level of biomarkers in the treatment groups was significantly decreased (P < 0.05) when compared with the GalN/LPS group. The results revealed that isoliquiritigenin exhibited better hepatoprotective activity than liquiritigenin and its derivatives.