Synthesis, antimalarial, antileishmanial, and antimicrobial activities of some 8-quinolinamine analogues

Aminoquinoline-Pyrimidine-Based Alkyl-Piperazine Tethered Hybrids: Synthesis, Antiplasmodial Activity, and Mechanistic Studies

Though great progress has been made to eliminate malaria globally, effective and inexpensive strategies to design new antimalarials are still required due to the problem of drug resistance to the currently used antimalarials. Herein, in continuation of our efforts to improve the therapeutic efficacy of 4-aminoquinoline-pyrimidine (4-AQ-Py) based molecular hybrids, a series of 4-AQ-Py hybrids linked through diamine-piperazine (flexible and rigid) linkers was synthesized and assessed for in vitro antiplasmodial activity. In the in vitro assay, these hybrids exhibited excellent potency and selectivity index against both the chloroquine (CQ)-sensitive (D6) and CQ-resistant (W2) strains of Plasmodium falciparum. Compound 7i was found to be the most potent (5-fold more active than CQ) against the D6 strain, while compound 7e displayed the most potency (53-fold more potent than CQ) against the W2 strain. Furthermore, nine compounds (7d, 7f-i, 7l, and 7o-q) showed better antiplasmodial activity than the reference drug artemisinin (ART) against the D6 strain, and compared to ART, seven compounds (7d-e, 7i-k, and 7p-q) demonstrated better activity against the W2 strain. All the synthesized hybrids were found noncytotoxic against the mammalian VERO cell lines. Two potent compounds, 7e and 7i, were evaluated for their in vivo antiplasmodial activity against P. berghei-infected mouse models. Additionally, one of the best active compounds, 7i, was tested for heme binding, and docking studies were conducted with Pf-DHFR to determine the primary mechanism of action of these hybrids.

Cp*Co(III)-Catalyzed C(8)-Nucleophilic Cascade Cyclization of Quinoline N-Oxide with 1,6-Enyne

The C(8)-selective nucleophilic cascade cyclization of quinoline N-oxide with easily derived 1,6-enyne from phenol derivatives is demonstrated. A variety of quinoline N-oxide and alkynes are discovered to be suitable for producing a library of quinoline N-oxide tethered cis-hydrobenzofurans with high yields and excellent functional group tolerance. The utility of the protocol has been accomplished by post-synthetic modification of the cyclized product. The mechanistic studies indicate a base-assisted internal electrophilic-type substitution (BIES)-type pathway for C-H bond activation, and electrospray ionization mass spectrometry (ESI-MS) analysis of the stoichiometric reaction confirmed the formation of a key five-membered cobaltacycle.

Four new phenolics and antiparasitic secondary metabolites from Flacourtia rukam Zoll. & Mortizi

Phytochemical investigation of Flacourtia rukam Zoll. & Mortizi (F. rukam) leaves and bark led to the isolation and characterization of seventeen compounds of which four phenolics were not previously described; 2-[(benzoyloxy)methyl]-phenyl-O-β-xylosyl-(1→2)-β-glucopyranoside (1), 2-[(benzoyloxy)methyl]-4-hydroxyphenyl-O-β-xylosyl-(1→2)-β-D-glucopyranoside (2), 2-hydroxy-5-(2-hydroxyphenoxy)phenoxy-β-glucopyranoside (3) and biphenyl-1,1',2,2'-tetraol (5). Interestingly, the later compound is known as a synthetic but this is the first report for its isolation from nature. Chemical structures were established using extensive analysis of spectroscopic data (1 D and 2 D NMR and HRESIMS). Biphenyl-1,1,2,2'-tetrol (5) exhibited a good activity against Trypanosoma brucei trypomastigotes with IC₅₀= 6.66 ug/mL. Compounds 2, 5, 9, 10, 11 and 12 showed a good in-vitro anti-inflammatory activity using proteinase inhibitory assay. On the contrary, all tested compounds were inactive as antileishmanial or antimalarial.

Recent advances in the global ring functionalization of 7-azaindoles

The 7-azaindole building block has attracted considerable interest in the field of drug discovery in the current portfolio. Because of their powerful medicinal properties, the development of synthetic, elegant techniques for the functionalization of 7-azaindoles continues to be an active area of research. Advances in metal-catalyzed chemistry have recently supported the successful development of a number of novel and effective methods for functionalization of the 7-azaindole template. This review reports state-of-the-art functionalization chemistry of 7-azaindoles with an aspiration to highlight the global ring functionalization of 7-azaindoles that are potential as pharmacophores for various therapeutic targets. Other relevant reviews focused on 7-azaindole synthesis, properties and applications have also been reported. However, none of these reviews have been dedicated to the results achieved in the field of metal-catalyzed cross-coupling/C-H bond functionalized reactions. So we wish to discuss and summarize the advances made since 2011 in this field toward 7-azaindole functionalization.

Discovery of a natural fluorescent probe targeting the Plasmodium falciparum cysteine protease falcipain-2

The Plasmodium falciparum cysteine protease falcipain-2 (FP-2) is an attractive antimalarial target. Here, we discovered that the natural compound NP1024 is a nonpeptidic inhibitor of FP-2 with an IC₅₀ value of 0.44 μmol L^-1. The most exciting finding is that both in vitro and in vivo, NP1024 directly targets FP-2 in malaria parasite-infected erythrocytes as a natural fluorescent probe, thereby paving the way for an integration of malaria diagnosis and treatment.

Synthesis and Biological Evaluation of 8-Quinolinamines and Their Amino Acid Conjugates as Broad-Spectrum Anti-infectives

In the search of therapeutic agents for emerging drug-resistant parasites, the synthesis of newer classes of 8-quinolinamines has emerged as a successful chemotherapeutic approach. We report synthesis of 8-quinolinamines bearing 5-alkoxy, 4-methyl, and 2-tert-butyl groups in the quinoline framework and their amino acid conjugates as broad-spectrum anti-infectives. 8-Quinolinamines exhibited potent in vitro antimalarial activity [IC50 = 20-4760 ng/mL (drug-sensitive Plasmodium falciparum D6 strain) and IC50 = 22-4760 ng/mL (drug-resistant P. falciparum W2 strain)]. The most promising analogues have cured all animals at 25 mg/kg/day against drug-sensitive Plasmodium berghei and at 50 mg/kg/day against multidrug-resistant Plasmodium yoelii nigeriensis infections in Swiss mice. The in vitro antileishmanial activities (IC50 = 0.84-5.0 μg/mL and IC90 = 1.95-7.0 μg/mL) comparable to standard drug pentamidine were exhibited by several of the synthesized 8-quinolinamines. At the same time, very promising antifungal activities (Candida albicans-IC50 = 4.93-19.38 μg/mL; Candida glabrata-IC50 = 3.96-19.22 μg/mL; Candida krusei-IC50 = 2.89-18.95 μg/mL; Cryptococcus neoformans-IC50 = 0.67-18.64 μg/mL; and Aspergillus fumigatus-IC50 = 6.0-19.32 μg/mL) and antibacterial activities (Staphylococcus aureus-IC50 = 1.33-18.9 μg/mL; methicillin-resistant S. aureus-IC50 = 1.38-15.34 μg/mL; and Mycobacterium intracellulare-IC50 = 3.12-20 μg/mL) were also observed. None of the 8-quinolinamines exhibited cytotoxicity and therefore are a promising structural class of compounds as antiparasitic and antimicrobials.

Cyclopiperettine, A New Amide from Piper nigrum

Cyclopiperettine, a new amide, was isolated from essential oil of Piper nigrum L. together with ten known compounds, including amides, monoterpenoids, and sesquiterpenoids. The structure of cyclopiperettine was established by 1D- and 2D- NMR and GC-MS techniques. Known compounds were identified as α-humulene, β-caryophyllene, caryophyllenol-II, β-elemene, elemol, 1-terpinen-4-ol, nerolidol, pellitorine, piperolein B and piperine. The crude oil and isolated compounds exhibited no antimicrobial activity against seven microbial strains up to 20 μg/mL.

Prenylated flavonoids from the stems and roots of Tripterygium wilfordii

Phytochemical investigation on the stems and roots of Tripterygium wilfordii led to the isolation and characterization of three new prenylated flavanones, tripteryols A-C (1-3), along with (±)-5,4'-dihydroxy-2'-methoxy-6',6″-dimethypyraro-(2″,3″:7,8)-6-methyflavanone (4), and ((2S)-5,7,4'-trihydroxy-2'-methoxy-8,5'-di(3-methyl-2-butenyl)-6-methylflavanone (5). Structures of the compounds 1-5 were elucidated using spectroscopic techniques, such as UV, IR, NMR (1D and 2D), and HRESI-MS. Tripteryols B (2) was found active in the antimicrobial assay against Cryptococcus neoformans, Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecalis (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) with IC₅₀ values in the range of 2.95-8.59μg/mL. Compounds 4 and 5 showed significant antimicrobial activities against C. neoformans, MRSA and Staphylococcus aureus with IC₅₀ values in the range of 1.06-2.60μg/mL. Additionally, significant antimalarial activities of tripteryols A-B (1-2) against chloroquine-sensitive D6 and resistant W2 clones of Plasmodium falciparum were observed and none of the compounds 1-5 were cytotoxic to Vero cells.

N-Piperonyl substitution on aminoquinoline-pyrimidine hybrids: Effect on the antiplasmodial potency

A series of 4-aminoquinoline-piperonyl-pyrimidine hybrids were synthesized with the aim of identifying compounds with enhanced antimalarial activity. All the synthesized molecules were evaluated in vitro against cultured Plasmodium falciparum W2 and D6 strains and exhibited potent antiplasmodial activities with IC₅₀ values in the range of 0.02-5.16 μM. Out of the 22 synthesised hybrids, 12 were found to be better (up to eight-fold more active) than chloroquine (CQ), particularly against the CQ-resistant W2 strain of P. falciparum with no significant cytotoxicity towards the mammalian cells. Mechanistic studies reveal that these compounds bind with heme and computational docking studies showed good docking interactions within the active site of Pf-DHFR.

Antimalarial and antimicrobial activities of 8-Aminoquinoline-Uracils metal complexes

8-Aminoquinoline (8AQ) derivatives have been reported to have antimalarial, anticancer, and antioxidant activities. This study investigated the potency of 8AQ-5-substituted (iodo and nitro) uracils metal (Mn, Cu, Ni) complexes (1-6) as antimalarial and antimicrobial agents. Interestingly, all of these metal complexes (1-6) showed fair antimalarial activities. Moreover, Cu complexes 2 (8AQ-Cu-5Iu) and 5 (8AQ-Cu-5Nu) exerted antimicrobial activities against Gram-negative bacteria including P. shigelloides and S. dysenteriae. The results reveal application of 8AQ and its metal complexes as potential compounds to be further developed as novel antimalarial and antibacterial agents.

"Wild cannabis": A review of the traditional use and phytochemistry of Leonotis leonurus

ETHNOPHARMACOLOGICAL RELEVANCE

Leonotis leonurus, locally commonly known as "wilde dagga" (=wild cannabis), is traditionally used as a decoction, both topically and orally, in the treatment of a wide variety of conditions such as haemorrhoids, eczema, skin rashes, boils, itching, muscular cramps, headache, epilepsy, chest infections, constipation, spider and snake bites. The dried leaves and flowers are also smoked to relieve epilepsy. The leaves and flowers are reported to produce a mild euphoric effect when smoked and have been said to have a similar, although less potent, psychoactive effect to cannabis.

AIM OF THE REVIEW

To amalgamate the botanical aspects, ethnopharmacology, phytochemistry, biological activity, toxicity and commercial aspects of the scientific literature available on L. leonurus.

METHODS

An extensive review of the literature from 1900 to 2015 was carried out. Electronic databases including Scopus, SciFinder, Pubmed, Google Scholar and Google were used as data sources. All abstracts, full-text articles and books written in English were considered.

RESULTS

The phytochemistry of particularly the non-volatile constituents of L. leonurus has been comprehensively investigated due to interest generated as a result of the wide variety of biological effects reported for this plant. More than 50 compounds have been isolated and characterised. L. leonurus contains mainly terpenoids, particularly labdane diterpenes, the major diterpene reported is marrubiin. Various other compounds have been reported by some authors to have been isolated from the plant, including, in the popular literature only, the mildly psychoactive alkaloid, leonurine. Leonurine has however, never been reported by any scientific analysis of the extracts of L. leonurus.

CONCLUSION

Despite the publication of various papers on L. leonurus, there is still, however, the need for definitive research and clarification of other compounds, including alkaloids and essential oils from L. leonurus, as well as from other plant parts, such as the roots which are extensively used in traditional medicine. The traditional use by smoking also requires further investigation as to how the chemistry and activity are affected by this form of administration. Research has proven the psychoactive effects of the crude extract of L. leonurus, but confirmation of the presence of psychoactive compounds, as well as isolation and characterization, is still required. Deliberate adulteration of L. leonurus with synthetic cannabinoids has been reported recently, in an attempt to facilitate the marketing of these illegal substances, highlighting the necessity for refinement of appropriate quality control processes to ensure safety and quality. Much work is therefore still required on the aspect of quality control to ensure safety, quality and efficacy of the product supplied to patients, as this plant is widely used in South Africa as a traditional medicine. Commercially available plant sources provide a viable option for phytochemical research, particularly with regard to the appropriate validation of the plant material (taxonomy) in order to identify and delimit closely related species such as L. leonurus and L. nepetifolia which are very similar in habit.

Eleven Microbial Metabolites of 6-Hydroxyflavanone

6-Hydroxyflavanone (1) when fermented with fungal culture Cunninghamella blakesleeana (ATCC 8688a) yielded flavanone 6-O-β-D-glucopyranoside (2), flavanone 6-sulfate (3), and 6-hydroxyflavanone 7-sulfate (4). Aspergillus alliaceus (ATCC 10060) also transformed 1 to metabolite 3 as well as 4'-hydroxyflavanone 6-sulfate (5) and 6,4'-dihydroxyflavanone (6). Beauveria bassiana (ATCC 7159) metabolized 1 to 6 and flavanone 6-O-β-D-4-O-methyglucopyranoside (7). Mucor ramannianus (ATCC 9628) transformed 1 to 2,4-cis-6-hydroxyflavan-4-ol (8), 2,4-trans-6-hydroxyflavan-4-ol (9), 2,4-trans-6,4'-dihydroxyflavan-4-ol 5-sulfate (10), 1,3-cis-1-methoxy-1-(2,5-dihydroxyphenyl)-3-phenylpropane (11) and 2,4-trans-flavan-4-ol 6-sulfate (12). Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antimalarial activities against selected organisms. However, weak antileishmanial activity was observed for metabolite 11 when tested against Leishmania donovani.

4-Aminoquinoline-pyrimidine-aminoalkanols: synthesis, in vitro antimalarial activity, docking studies and ADME predictions

4-Aminoquinoline-pyrimidine-aminoalkanols displaying good in vitro antimalarial activities against both CQ-sensitive and -resistant strains of P. falciparum, together with favourable resistance-indices and the predicted ADME properties, are reported.

A new enniatin antibiotic from the endophyte Fusarium tricinctum Corda

Enniatins (ENs), a group of antibiotics commonly produced by various strains of Fusarium, are six-membered cyclic depsipeptides formed by the union of three molecules of D-α-hydroxyisovaleric acid and three N-methyl-L-amino acids. The endophyte Fusarium tricinctum Corda was isolated from the fruits of Hordeum sativum Jess. and cultivated on a rice medium. The fungal metabolites were extracted with methanol and were identified, employing liquid chromatography-mass spectrometry as ENs A, A1, B, B1, B2 and Q. EN Q is a new analog of EN A and the occurrence of EN B2 is reported for the first time from this endophyte, in addition to four well-known ENs (A, A1, B and B1). The methanol extract of F. tricinctum showed mild antibacterial and antileishmanial activities. Additionally the tested extract displayed inhibition of the activity of thioredoxin reductase enzyme of Plasmodium falciparum.

High-throughput screening identifies Ceefourin 1 and Ceefourin 2 as highly selective inhibitors of multidrug resistance protein 4 (MRP4)

Multidrug resistance protein 4 (MRP4/ABCC4), a member of the ATP-binding cassette (ABC) transporter superfamily, is an organic anion transporter capable of effluxing a wide range of physiologically important signalling molecules and drugs. MRP4 has been proposed to contribute to numerous functions in both health and disease; however, in most cases these links remain to be unequivocally established. A major limitation to understanding the physiological and pharmacological roles of MRP4 has been the absence of specific small molecule inhibitors, with the majority of established inhibitors also targeting other ABC transporter family members, or inhibiting the production, function or degradation of important MRP4 substrates. We therefore set out to identify more selective and well tolerated inhibitors of MRP4 that might be used to study the many proposed functions of this transporter. Using high-throughput screening, we identified two chemically distinct small molecules, Ceefourin 1 and Ceefourin 2, that inhibit transport of a broad range of MRP4 substrates, yet are highly selective for MRP4 over other ABC transporters, including P-glycoprotein (P-gp), ABCG2 (Breast Cancer Resistance Protein; BCRP) and MRP1 (multidrug resistance protein 1; ABCC1). Both compounds are more potent MRP4 inhibitors in cellular assays than the most widely used inhibitor, MK-571, requiring lower concentrations to effect a comparable level of inhibition. Furthermore, Ceefourin 1 and Ceefourin 2 have low cellular toxicity, and high microsomal and acid stability. These newly identified inhibitors should be of great value for efforts to better understand the biological roles of MRP4, and may represent classes of compounds with therapeutic application.

Synthesis, characterization, antimicrobial, DNA cleavage, and in vitro cytotoxic studies of some metal complexes of schiff base ligand derived from thiazole and quinoline moiety

A novel Schiff base ligand N-(4-phenylthiazol-2yl)-2-((2-thiaxo-1,2-dihydroquinolin-3-yl)methylene)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-thioxo-1,2-dihydroquinoline-3-carbaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), and Zn(II) complexes have been characterized by elemental analysis and various spectral studies like FT-IR, (1)H NMR, ESI mass, UV-Visible, ESR, TGA/DTA, and powder X-ray diffraction studies. The Schiff base ligand (L) behaves as tridentate ONS donor and forms the complexes of type [ML(Cl)2] with square pyramidal geometry. The Schiff base ligand (L) and its metal complexes have been screened in vitro for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleavage activity of ligand and its metal complexes were studied using plasmid DNA pBR322 as a target molecule by gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties for the ligand and its metal complexes against Artemia salina. The results showed that the biological activities of the ligand were found to be increased on complexation.

Synthesis, antimalarial activity, heme binding and docking studies of 4-aminoquinoline–pyrimidine based molecular hybrids

A series of novel 4-aminoquinoline–pyrimidine hybrids was synthesized and evaluated for their antimalarial activity.

Synthesis of piperazine tethered 4-aminoquinoline-pyrimidine hybrids as potent antimalarial agents

Piperazine linked 4-aminoquinoline-pyrimidine hybrids were synthesized and evaluated for in vitro antimalarial activity against W2 and D6 strains of plasmodium falciparum.

Triazine–pyrimidine based molecular hybrids: synthesis, docking studies and evaluation of antimalarial activity

A series of novel triazine–pyrimidine hybrids have been synthesized and evaluated for their in vitro antimalarial activity.

Bioconversion of 7-hydroxyflavanone: isolation, characterization and bioactivity evaluation of twenty-one phase I and phase II microbial metabolites

Microbial metabolism of 7-hydroxyflavanone (1) with fungal culture Cunninghamella blakesleeana (ATCC 8688a), yielded flavanone 7-sulfate (2), 7,4'-dihydroxyflavanone (3), 6,7-dihydroxyflavanone (4), 6-hydroxyflavanone 7-sulfate (5), and 7-hydroxyflavanone 6-sulfate (6). Mortierella zonata (ATCC 13309) also transformed 1 to metabolites 2 and 3 as well as 4'-hydroxyflavanone 7-sulfate (7), flavan-4-cis-ol 7-sulfate (8), 2',4'-dihydroxychalcone (9), 7,8-dihydroxyflavanone (10), 8-hydroxyflavanone 7-sulfate (11), and 8-methoxy-7-hydroxyflavanone (12). Beauveria bassiana (ATCC 7159) metabolized 1 to 2, 3, and 8, flavanone 7-O-β-D-O-4-methoxyglucopyranoside (13), and 8-hydroxyflavanone 7-O-β-D-O-4-methoxyglucopyranoside (14). Chaetomium cochlioides (ATCC 10195) also transformed 1 to 2, 3, 9, together with 7-hydroxy-4-cis-ol (15). Mucor ramannianus (ATCC 9628) metabolized 1 in addition to 7, to also 4,2',4'-trihydroxychalcone (16), 7,3',4'-trihydroxyflavanone (17), 4'-hydroxyflavanone 7-O-α-L-rhamnopyranoside (18), and 7,3',4'-trihydroxy-6-methoxyflavanone (19). The organism Aspergillus alliaceus (ATCC 10060) transformed 1 to metabolites 3, 16, 7,8,4'-trihydroxyflavanone (20), and 7-hydroxyflavanone 4'-sulfate (21). A metabolite of 1, flavanone 7-O-β-D-O-glucopyranoside (22) was produced by Rhizopus oryzae (ATCC 11145). Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antimalarial activities against selected organisms. Metabolites 4 and 16 showed weak antileishmanial activity.

Novel 4-aminoquinoline-pyrimidine based hybrids with improved in vitro and in vivo antimalarial activity

A class of hybrid molecules consisting of 4-aminoquinoline and pyrimidine were synthesized and tested for antimalarial activity against both chloroquine (CQ)-sensitive (D6) and chloroquine (CQ)-resistant (W2) strains of Plasmodium falciparum through an in vitro assay. Eleven hybrids showed better antimalarial activity against both CQ-sensitive and CQ-resistant strains of P. falciparum in comparison to standard drug CQ. Four molecules were more potent (7-8-fold) than CQ in D6 strain, and eight molecules were found to be 5-25-fold more active against resistant strain (W2). Several compounds did not show any cytotoxicity up to a high concentration (60 μM), others exhibited mild toxicities, but the selective index for the antimalarial activity was very high for most of these hybrids. Two compounds selected for in vivo evaluation have shown excellent activity (po) in a mouse model of Plasmodium berghei without any apparent toxicity. The X-ray crystal structure of one of the compounds was also determined.

Antiparasitic antioxidant phenylpropanoids and iridoid glycosides from Tecoma mollis

A radical scavenging guided phytochemical study on the stem bark of Tecoma mollis afforded seven active phenylpropanoid glycosides (1-7), including a new one (4), and one iridoid (8). The structures of the isolated compounds were elucidated on the basis of spectroscopic evidences and correlated with known compounds. Compounds (1-7) displayed promising antioxidant activity (DPPH assay) in relation to ascorbic acid (positive control). The antimicrobial activity for compounds (1-8) was evaluated against five bacterial and five fungal strains. The isolated compounds exhibited nonselective weak to moderate antimicrobial activity. The highest antileishmanial activity against Leishmania donovani was observed for compound (7) with an IC₅₀ value of 6.71 μg/ml, using pentamidine and amphotericin B as drug controls. Compound (5) exhibited moderate antimalarial activity (45% inhibition) against chloroquine sensitive (D6) clones of Plasmodium falciparum.

Alkyl phenols and saponins from the roots of Labisia pumila (Kacip Fatimah)

Recently, there is a remarkable boom in the sales of Labisia pumila (Kacip Fatimah) in the Malaysian market, as an extract of the plant is used to gain energy and libido as well as to treat many other ailments. A chemical analysis of its roots was undertaken and three metabolites, demethylbelamcandaquinone B (1), fatimahol (2), and dexyloprimulanin (3) together with 21 known compounds including epoxyoleanane glycosides, alkenated phenolics, cerebroside, glycerogalactolipids, and lipids were isolated and identified. Structure elucidation was achieved by spectroscopic and chemical studies. The MeOH extract of KF and compounds 12 and 13 exhibited moderate in vitro antibacterial activity.

Microbial metabolism. Part 12. Isolation, characterization and bioactivity evaluation of eighteen microbial metabolites of 4'-hydroxyflavanone

Fermentation of 4'-hydroxyflavanone (1) with fungal cultures, Beauveria bassiana (ATCC 13144 and ATCC 7159) yielded 6,3',4'-trihydroxyflavanone (2), 3',4'-dihydroxyflavanone 6-O-β-D-4-methoxyglucopyranoside (3), 4'-hydroxyflavanone 3'-sulfate (4), 6,4'-dihydroxyflavanone 3'-sulfate (5) and 4'-hydroxyflavanone 6-O-β-D-4-methoxyglucopyranoside (7). B. bassiana (ATCC 13144) and B. bassiana (ATCC 7159) in addition, gave one more metabolite each, namely, flavanone 4'-O-β-D-4-methoxyglucopyranoside (6) and 6,4'-dihydroxyflavanone (8) respectively. Cunninghamella echinulata (ATCC 9244) transformed 1 to 6,4'-dihydroxyflavanone (8), flavanone-4'-O-β-D-glucopyranoside (9), 3'-hydroxyflavanone 4'-sulfate (10), 3',4'-dihydroxyflavanone (11) and 4'-hydroxyflavanone-3'-O-β-D-glucopyranoside (12). Mucor ramannianus (ATCC 9628) metabolized 1 to 2,4-trans-4'-hydroxyflavan-4-ol (13), 2,4-cis-4'-hydroxyflavan-4-ol (14), 2,4-trans-3',4'-dihydroxyflavan-4-ol (15), 2,4-cis-3',4'-dihydroxyflavan-4-ol (16), 2,4-trans-3'-hydroxy-4'-methoxyflavan-4-ol (17), flavanone 4'-O-α-D-6-deoxyallopyranoside (18) and 2,4-cis-4-hydroxyflavanone 4'-O-α-D-6-deoxyallopyranoside (19). Metabolites 13 and 14 were also produced by Ramichloridium anceps (ATCC 15672). The former was also produced by C. echinulata. Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antiprotozoal activities against selected organisms.

4,4'-Methylenebis{N-[(E)-quinolin-2-yl-methylidene]aniline}

The title compound, C(33)H(24)N(4), was prepared by the reaction of a bifunctional aromatic diamine (4,4'-diamino-diphenyl-methane) and an aldehyde (quinoline-2-carboxaldhyde). The mol-ecule consists of two nearly planar (or r.m.s. deviation = 0.017 Å) 4-methyl-N-[(E)-quinolin-2-yl-methyl-idene]aniline moieties, which are linked by the methyl-ene group. The angle between the mean planes of the two benzene rings connected to the methyl-ene group is 77.86 (11)°.

4,4'-Oxybis{N-[(E)-quinolin-2-yl-methyl-idene]aniline}

The title Schiff base compound, C(32)H(22)N(4)O, was prepared by a reaction of 4,4'-diamino-diphenyl ether and 2-quinoline-carboxaldehyde. The mol-ecule consists of two 4-{N-[(E)-quinolin-2-yl-methyl-idene]amino}-phenyl units linked by an oxygen bridge. The dihedral angles between two benzene rings and between the two quinoline ring systems are 53.81 (7) and 42.56 (4)°, respectively. Inter-molecular C-H⋯N hydrogen bonding is present in the crystal structure.

Structures, targets and recent approaches in anti-leishmanial drug discovery and development

Recent years have seen a significant improvement in available treatment options for leishmaniasis. Two new drugs, miltefosine and paromomycin, have been registered for the treatment of visceral leishmaniasis (VL) in India since 2002. Combination therapy is now explored in clinical trials as a new treatment approach for VL to reduce the length of treatment and potentially prevent selection of resistant parasites. However there is still a need for new drugs due to safety, resistance, stability and cost issues with existing therapies. The search for topical treatments for cutaneous leishmaniasis (CL) is ongoing. This review gives a brief overview of recent developments and approaches in anti-leishmanial drug discovery and development.

Synthesis, antiprotozoal, antimicrobial, β-hematin inhibition, cytotoxicity and methemoglobin (MetHb) formation activities of bis(8-aminoquinolines)

In continuing our search of potent antimalarials based on 8-aminoquinoline structural framework, three series of novel bis(8-aminoquinolines) using convenient one to four steps synthetic procedures were synthesized. The bisquinolines were evaluated for in vitro antimalarial (Plasmodiumfalciparum), antileishmanial (Leishmaniadonovani), antimicrobial (a panel of pathogenic bacteria and fungi), cytotoxicity, β-hematin inhibitory and methemoglobin (MetHb) formation activities. Several compounds exhibited superior antimalarial activities compared to parent drug primaquine. Selected compounds (44, 61 and 79) when tested for in vivo blood-schizontocidal antimalarial activity (Plasmodiumberghei) displayed potent blood-schizontocial activities. The bisquinolines showed negligible MetHb formation (0.2-1.2%) underlining their potential in the treatment of glucose-6-phosphate dehydrogenase deficient patients. The bisquinoline analogues (36, 73 and 79) also exhibited promising in vitro antileishmanial activity, and antimicrobial activities (43, 44 and 76) against a panel of pathogenic bacteria and fungi. The results of this study provide evidence that bis(8-aminoquinolines), like their bis(4-aminoquinolines) and artemisinin dimers counterparts, are a promising class of antimalarial agents.

Identification of 3-phenylaminoquinolinium and 3-phenylaminopyridinium salts as new agents against opportunistic fungal pathogens

Previous studies on the indoloquinoline alkaloid, cryptolepine (2), revealed that it has antii-nfective properties among other activities. Using Structure-activity relationship (SAR) techniques, several ring-opened analogs of cryptolepine (3-phenylaminopyridinium and 3-phenylaminoquinolinium derivatives) were designed to improve the potency and lower the cytotoxicity shown by several of the precursor agents. Results indicate that these ring-opened analogs constitute new anti-infective agents with over a 100-fold potency and several fold lower cytotoxicity than cryptolepine from which they are derived.

Structural modifications of quinoline-based antimalarial agents: Recent developments

Antimalarial drugs constitute a major part of antiprotozoal drugs and have been in practice for a long time. Antimalarial agents generally belong to the class of quinoline which acts by interfering with heme metabolism. The recent increase in development of chloroquine-resistant strains of Plasmodium falciparum and failure of vaccination program against malaria have fuelled the drug discovery program against this old and widespread disease. Quinoline and its related derivative comprise a class of heterocycles, which has been exploited immensely than any other nucleus for the development of potent antimalarial agents. Various chemical modifications of quinoline have been attempted to achieve analogs with potent antimalarial properties against sensitive as well as resistant strains of Plasmodium sp., together with minimal potential undesirable side effects. This review outlines essentially some of the recent chemical modifications undertaken for the development of potent antimalarial agents based on quinoline.

Antiprotozoal, anticancer and antimicrobial activities of dihydroartemisinin acetal dimers and monomers

Nine dihydroartemisinin acetal dimers (6-14) with diversely functionalized linker units were synthesized and tested for in vitro antiprotozoal, anticancer and antimicrobial activity. Compounds 6, 7 and 11 [IC(50): 3.0-6.7 nM (D6) and 4.2-5.9 nM (W2)] were appreciably more active than artemisinin (1) [IC(50): 32.9 nM (D6) and 42.5 nM (W2)] against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of the malaria parasite, Plasmodium falciparum. Compounds 10, 13 and 14 displayed enhanced anticancer activity in a number of cell lines compared to the control drug, doxorubicin. The antifungal activity of 7 and 12 against Cryptococcus neoformans (IC(50): 0.16 and 0.55 microM, respectively) was also higher compared to the control drug, amphotericin B. The antileishmanial and antibacterial activities were marginal. A number of dihydroartemisinin acetal monomers (15-17) and a trimer (18) were isolated as byproducts from the dimer synthesis and were also tested for biological activity.