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PubMed2005

Synthesis and structure-activity correlation studies of metal complexes of alpha-N-heterocyclic carboxaldehyde thiosemicarbazones in Shewanella oneidensis.

This investigation involved the synthesis of metal complexes to test the hypothesis that structural changesand metal coordination in pyridine thiosemicarbazones affect cell growth and cell proliferation in vitro. Thiosemicarbazones are well known to possess antitumor, antiviral, antibacterial, antimalarial, and other activities. Extensive research has been carried out on aliphatic, aromatic, heterocyclic and other types of thiosemicarbazones and their metal complexes. Due to the pronounced reactivity exhibited by metal complexes of heterocyclic thiosemicarbazones, synthesis and structural characterization of di-2-pyridylketone 4N-phenyl thiosemicarbazone and diphenyl tin (Sn) and platinum (Pt) complexes were undertaken. Shewanella oneidensis MR-1, a metal ion-reducing bacterium, was used as a model organism to explore the biological activity under aerobic conditions. A comparision of the cytotoxic potential of selected ligand and metal-complex thiosemicarbazones on cell growth in wild type MR-1 and mutant DSP-010 Shewanella oneidensis strains at various concentrations (0, 5, 10, 15, 20 or 25 ppm) was performed. The wild type (MR-1) grown in the presence of increasing concentrations of Sn- thiosemicarbazone complexes was comparatively more sensitive (mean cell number = 4.8 X 10(8) +/- 4.3 X 10(7) SD) than the DSP-010, a spontaneous rifampicillin derivative of the parent strain (mean cell number = 5.6 x 10(8) +/- 6.4 X 10(7) SD) under comparable aerobic conditions (p = 0.0004). No differences were observed in the sensitivity of the wild and mutant types when exposed to various concentrations of diphenyl Pt- thiosemicarbazone complex (p = 0.425) or the thiosemicarbazone ligand (p = 0.313). Growth of MR-1 in the presence of diphenyl Sn-thiosemicarbazone was significantly different among treatment groups (p = 0.012). MR-1 cell numbers were significantly higher at 5ppm than at 10 to 20ppm (p = 0.05). The mean number of DSP-010 variant strain cells also differed among diphenyl Sn- thiosemicarbazone complex treated groups (p = 0.051). In general, there was an increasing trend in the number of cells from about 5.0 X 10(8) cells (methanol control group) to about 6.0 X 10(8) cells (25ppm). The number of cells in methanol control group was significantly lower than cell numbers at 20ppm and 25ppm (p = 0.05), and numbers at 5ppm treatment were lower than at 20 and 25ppm (p = 0.05). Furthermore, a marginally significant difference in the number of MR-1 cells was observed among diphenyl Pt- thiosemicarbazone complex treatment groups (p = 0.077), and an increasing trend in the number of cells was noted from approximately 5.0 X 10(8) cells (methanol control group) to approximately 5.8 X 10(8) cells (20ppm). In contrast, the DSP-010 variant strain showed no significant differences in cell numbers when treated with various concentrations of diphenyl Pt- thiosemicarbazone complex (p = 0.251). Differences in response to Sn- metal complex between MR-1 and DSP-010 growing cultures indicate that biological activity to thiosemicarbazone metal complexes may be strain specific.

Colony Count, Microbial↗
PubMed2000

The cytotoxicity of symmetrical and unsymmetrical bis(thiosemicarbazones) and their metal complexes in murine and human tumor cells.

A number of thiosemicarbazones have been tested previously and herein are included three bis(thiosemicarbazones) for comparison to the previous derivatives. In general the uncomplexed thiosemicarbazones were more potent in the cytotoxic screens than the bis(thiosemicarbazone) except in the murine L1210 and the human colon SW480 screens. Mode of action studies have only demonstrated slight differences in the effects of the two types of compounds on nucleic acid metabolism. The symmetrical and unsymmetrical bis(thiosemicarbazones) complexes of copper, nickel, zinc, and cadmium have been examined to compare them to the heterocyclic N(4)-substituted thiosemicarbazones metal complexes. These new derivatives demonstrated excellent activity against the growth of suspended lymphomas and leukemias although it should be pointed out that generally they were not as active as the copper complexes of N(4)-substituted thiosemicarbazones. Nevertheless, selected bis(thiosemicarbazones) complexes were active against the growth of human lung MB9812, KB nasopharynx, epidermoid A431, glioma UM-86, colon SW480, ovary 1-A9, breast MCK-7, and osteosarcoma Saos-2. In human HL-60 promyelocytic leukemia cells the complexes preferentially inhibited DNA and purine syntheses over 60 min. The regulatory enzyme of the de novo purine pathway, IMP dehydrogenase, appeared to be a major target of the complexes. However, minor inhibition of the activities of DNA polymerase alpha, PRPP-amido transferase, ribonucleotide reductase, and nucleoside kinases occurred over the same time period. No doubt these effects of the complexes on nucleic acid metabolism were additive since the d[NTP] pool levels were reduced after 60 min as was DNA synthesis. The symmetrical and unsymmetrical bis(thiosemicarbazones) and their metal complexes did not cause as severe DNA fragmentation as the heterocyclic N(4)-substituted thiosemicarbazone metal complexes; furthermore, their metabolic effects in the tumor cell were more focused on a single synthetic pathway.

Animals↗
PubMed2006

Bonding trends of thiosemicarbazones in mononuclear and dinuclear copper(I) complexes: syntheses, structures, and theoretical aspects.

Reactions of copper(I) halides with a series of thiosemicarbazone ligands (Htsc) in the presence of triphenylphosphine (Ph(3)P) in acetonitrile have yielded three types of complexes: (i) monomers, [CuX(eta1-S-Htsc)(Ph3P)2] [X, Htsc = I (1), Br (2), benzaldehyde thiosemicarbazone (Hbtsc); I (5), Br (6), Cl (7), pyridine-2-carbaldehyde thiosemicarbazone (Hpytsc)], (ii) halogen-bridged dimers, [Cu2(mu2-X)2(eta1-S-Htsc)2(Ph3P)2] [X, Htsc = Br (3), Hbtsc; I (8), furan-2-carbaldehyde thiosemicarbazone (Hftsc); I (11), thiophene-2-carbaldehyde thiosemicarbazone (Httsc)], and (iii) sulfur-bridged dimers, [Cu2X2(mu2-S-Htsc)2(Ph3P)2] [X, Htsc = Cl (4), Hbtsc; Br (9), Cl (10), pyrrole-2-carbaldehyde thiosemicarbazone (Hptsc); Br (12), Httsc]. All of these complexes have been characterized with the help of elemental analysis, IR, 1H, 13C, or 31P NMR spectroscopy, and X-ray crystallography (1-12). In all of the complexes, thiosemicarbazones are acting as neutral S-donor ligands in eta()S or mu2-S bonding modes. The Cu...Cu separations in the Cu(mu2-X)2Cu and Cu(mu2-S)2Cu cores lie in the ranges 2.981(1)-3.2247(6) and 2.813(1)-3.2329(8) Angstroms, respectively. The geometry around each Cu center in monomers and dimers may be treated as distorted tetrahedral. Ab initio density functional theory calculations on model monomeric and dimeric complexes of the simplest thiosemicarbazone [H2C=N-NH-C(S)-NH2, Htsc] have revealed that monomers and halogen-bridged dimers have similar stability and that sulfur-bridged dimers are stable only when halogen atoms are engaged in hydrogen bonding with the solvent of crystallization or H2O molecules.

Copper↗
PubMed2003

Synthesis, structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands.

Twelve zinc(II) complexes with thiosemicarbazone and semicarbazone ligands were prepared and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FT-IR and 1H and 13C NMR spectroscopy. Seven three-dimensional structures of zinc(II) complexes were determined by single-crystal X-ray analysis. Their antimicrobial activities were evaluated by MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 5- and 6-coordinate zinc(II) complexes with a tridentate thiosemicarbazone ligand (Hatsc), ([Zn(atsc)(OAc)](n) 1, [Zn(Hatsc)(2)](NO(3))(2).0.3H(2)O 2, [ZnCl(2)(Hatsc)] 3 and [Zn(SO(4))(Hatsc)(H(2)O)].H(2)O 4 [Hatsc=2-acetylpyridine(thiosemicarbazone)]), showed antimicrobial activities against test organisms, which were different from those of free ligands or the starting zinc(II) compounds. Especially, complex 2 showed effective activities against P. aeruginosa, C. albicans and moderate activities against S. cerevisiae and two molds. These facts are in contrast to the results that the 5- or 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridine-4N-morpholinethiosemicarbazone, ([Zn(mtsc)(2)].0.2EtOH 5, the previously reported catena-poly [Zn(mtsc)-mu-(OAc-O,O')](n) and [Zn(NO(3))(2)(Hmtsc)] [Hmtsc=2-acetylpyridine (4N-morpholyl thiosemicarbazone)]), showed no activities against the test microorganisms. The 5- and 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridinesemicarbazone, ([Zn(OAc)(2)(Hasc)] 6 and [Zn(Hasc)(2)](NO(3))(2) 7 [Hasc=2-acetylpyridine(semicarbazone)]), showed no antimicrobial activities against bacteria, yeasts and molds. Complex [ZnCl(2)(Hasc)] 8, which was isostructural to complex 3, showed modest activity against Gram-positive bacterium, B. subtilis. The 1:1 complexes of zinc(II) with pentadentate thiosemicarbazone ligands, ([Zn(dmtsc)](n) 9 and [Zn(datsc)](n) 10 [H(2)dmtsc=2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone) and H(2)datsc=2,6-diacetylpyridine bis(thiosemicarbazone)]), did not inhibit the growth of the test organisms. On the contrary, 7-coordinate zinc(II) complexes with one pentadentate semicarbazone ligand and two water molecules, ([Zn(H(2)dasc)(H(2)O)(2)](OAc)(2).5.3H(2)O 11 and [Zn(H(2)dasc)(H(2)O)(2)](NO(3))(2).H(2)O 12 [H(2)dasc=2,6-diacetylpyridine bis(semicarbazone)]), showed modest to moderate activities against bacteria. Based on the X-ray structures, the structure-activity correlation for the antimicrobial activities was elucidated. The zinc(II) complexes with 4N-substituted ligands showed no antimicrobial activities. In contrast to the previously reported nickel(II) complexes, properties of the ligands such as the ability to form hydrogen bonding with a counter anion or hydrated water molecules or the less bulkiness of the 4N moiety would be a more important factor for antimicrobial activities than the coordination number of the metal ion for the zinc(II) complexes.

Anti-Bacterial Agents↗
PubMed2006

Rhodium assisted C-H activation of benzaldehyde thiosemicarbazones and their oxidation via activation of molecular oxygen.

The benzaldehyde thiosemicarbazones are found to undergo oxidation at the sulfur center upon reaction with [Rh(PPh3)3Cl] in refluxing ethanol in the presence of a base (NEt3). A group of organorhodium complexes are obtained from such reactions, in which the oxidized thiosemicarbazones are coordinated to rhodium as tridentate CNS donors, along with two triphenylphosphines and a hydride. From the reaction with para-nitrobenzaldehyde thiosemicarbazone, a second organometallic complex is obtained, in which the thiosemicarbazone is coordinated to rhodium as a tridentate CNS donor, along with two triphenylphosphines and a hydride. Reaction of the benzaldehyde thiosemicarbazones with [Rh(PPh3)3Cl] in refluxing ethanol in the absence of NEt3 affords another group of organorhodium complexes, in which the thiosemicarbazones are coordinated to rhodium as tridentate CNS donors, along with two triphenylphosphines and a chloride. Structures of representative complexes of each type of complexes have been determined by X-ray crystallography. In all of the complexes, the two PPh3 ligands are trans. All of the complexes show intense MLCT transitions in the visible region. Cyclic voltammetry on these complexes shows a Rh(III)-Rh(IV) oxidation on the positive side of SCE. Redox responses of the coordinated thiosemicarbazones are also displayed by all of the complexes.

Benzaldehydes↗
PubMed1960

The structure-activity relationships of the antiviral chemotherapeutic activity of isatin beta-thiosemicarbazone.

As part of an investigation devoted to the development of new antiviral agents a compound of established antiviral activity has been subjected to systematic structural modification. The structure-activity data so obtained have been used in the design of new compounds, some of which are described. The compound chosen was isatin beta-thiosemicarbazone, which has high activity against neurovaccinia infection in mice, and a 4-point parallel-line assay of in vivo chemotherapeutic activity has been developed, which has enabled the activity of the derivatives to be determined against isatin beta-thiosemicarbazone as a standard. The overall dimensions of the isatin beta-thiosemicarbazone molecule appear to be nearly maximal for the retention of high activity, as all substituents in the aromatic ring decrease the activity irrespective of their nature or position. The projection of the -CS.NH(2) group in relation to the ring nitrogen was found to be critical, as the alpha-thiosemicarbazone was inactive. A number of modifications of the side-chain were investigated:all led to reduction or loss of antiviral activity. The antiviral activity showed a positive correlation with chloroform solubility over a considerable range. The most active compound encountered was 1-ethylisatin beta-thiosemicarbazone, with an activity of 286 (isatin beta-thiosemicarbazone identical with100). Isatin beta-thiosemicarbazone showed no activity against 15 other viruses, and 20 related compounds showed on activity against ectromelia.

Animals↗
PubMed2004

synthesis, characterization and in vitro antiamoebic activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones and their Palladium (II) and Ruthenium (II) complexes.

Synthesis of new Palladium(II) and Ruthenium(II) complexes of the type, [Pd(L)Cl(2)] and [Ru(eta(4)-C(8)H(12))(L)Cl(2)] [where, L = thiosemicarbazones derived from 5-nitrothiophene-2-carboxaldehyde and cycloalkylaminothiocarbonyl hydrazines] have been isolated by the reaction of [Pd(DMSO)(2)Cl(2)] and [Ru(eta(4)-C(8)H(12))(CH(3)CN)(2)Cl(2)] with 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones. The spectral data revealed that the thiosemicarbazones act as bidentate ligands, making use of thionic sulphur and the azomethine nitrogen atom for coordination to the central metal ion. Microdilution method was used for the assessment of antiamoebic activity of all the compounds against HK-9 strain of Entamoeba histolytica. Among all the thiosemicarbazones, 5-NT-4-BPTSCN (3) showed significant antiamoebic activity (IC(50) - 2.56 microM). Enhancement of antiamoebic activity resulted by introducing palladium and ruthenium metals in the thiosemicarbazone moiety. All the Pd(II) and Ru(II) complexes of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones were found more active then their respective ligands. The complexes 1a-4a, 1b and 3b showed antiamoebic activity.

Amebicides↗
PubMed2003

Synthesis, spectral studies and screening for amoebicidal activity of new palladium(II) complexes derived from thiophene-2-carboxaldehyde thiosemicarbazones.

In view of the antiamoebic properties observed for many thiophene-2-carboxaldehyde thiosemicarbazones, a series of N(4)-substituted thiosemicarbazones metal complexes derived from thiophene-2-carboxaldehyde was prepared for evaluation against Entamoeba histolytica. Reaction of thiophene-2-carboxaldehyde with cycloalkylaminothiocarbonylhydrazines having different amines gave the corresponding thiosemicarbazones. Reaction of latter with [Pd(DMSO)(2)Cl(2)] gave requisite palladium thiosemicarbazone complexes of the type [Pd(TSC)Cl(2)] (where TSC=thiosemicarbazones). Screening of antiamoebic activity of these compounds was assayed in vitro against (HM-1:1MSS) strain of E. histolytica. Enhancement of antiamoebic resulted from introducing palladium metal in the thiosemicarbazone moiety. Among the studied compounds, [Pd(2-TCA-1,2,3,4-THQTSC)Cl(2)] (2a) showed better activity.

Amebicides↗
PubMed1995

Synthesis and antitumor activity of 4- and 5-substituted derivatives of isoquinoline-1-carboxaldehyde thiosemicarbazone.

Various substituted isoquinoline-1-carboxaldehyde thiosemicarbazones (12 compounds) have been synthesized and evaluated for antineoplastic activity in mice bearing the L1210 leukemia. Condensation of 4-bromo-1-methylisoquinoline (4) with ammonium hydroxide, methylamine, ethylamine, and N-acetylethylenediamine gave the corresponding 4-amino, 4-methylamino, 4-ethylamino, and 4-N-(acetylethyl)amino derivatives, which were then converted to amides and subsequently oxidized to aldehydes followed by condensation with thiosemicarbazide to yield thiosemicarbazones 8a-c, 9a-c, and 16. Nitration of 4, followed by oxidation with selenium dioxide, produced aldehyde 18, which was then converted to the cyclic ethylene acetal 19. Condensation of 19 with morpholine followed by catalytic reduction of the nitro group and treatment with thiosemicarbazide afforded 5-amino-4-morpholinoisoquinoline-1-carboxaldehyde thiosemicarbazone (22). N-Oxidation of 1,5-dimethylisoquinoline, followed by rearrangement with acetic anhydride, gave, after acid hydrolysis, 1,5-dimethyl-4-hydroxyisoquinoline, which was converted to its acetate and then oxidized to yield 4-acetoxy-5-methylisoquinoline-1-carboxaldehyde (32). Sulfonation of 1,4-dimethylisoquinoline, followed by reaction with potassium hydroxide, acetylation, and oxidation, gave 5-acetoxy-4-methylisoquinoline-1-carboxaldehyde (40). Condensation of compounds 32 and 39 with thiosemicarbazide afforded the respective 4- and 5-acetoxy(5- and 4-methyl)thiosemicarbazones 33 and 40, which were then converted to their respective 4- and 5-hydroxy derivatives 34 and 41 by acid hydrolysis. The most active compounds synthesized were 4-aminoisoquinoline-1-carboxaldehyde thiosemicarbazone (9a) and 4-(methylamino)isoquinoline-1-carboxaldehyde thiosemicarbazone (9b), which both produced optimum % T/C values of 177 against the L1210 leukemia in mice when used at a daily dosage of 40 mg/kg for 6 consecutive days. Furthermore, when 9a was given twice daily at a dosage of 40 mg/kg for 6 consecutive days, a T/C value of 165 was obtained and 60% of the mice were 60-day long-term survivors.

Acetylation↗
PubMed1992

Antifungal and antitumor activity of heterocyclic thiosemicarbazones and their metal complexes: current status.

More than 75 substituted thiosemicarbazones and a number of metal complexes of each have been assayed for their antifungal activity. Their activity is significantly affected by the substituted groups attached at both 1N and 4N of the thiosemicarbazone moiety. Greatest activity occurs for 2-substituted pyridine thiosemicarbazones with differences observed for 2-formylpyridine, 2-acetylpyridine and 2-benzoylpyridine derivatives and their metal complexes. Further, there are activity differences for 4N-alkyl-, 4N-aryl-, 4N-dialkyl- and 3-azacyclothiosemicarbazones and their metal complexes as well as changes in the substituent size among each of these subgroups. Cu(II) complexes are often more active than the uncomplexed thiosemicarbazones, with the latter showing similar activity to Ni(II) complexes in many instances. The reduction potential of the thiosemicarbazone ligand in a Cu(II) complex, the strength of the ligand field and various spectral properties can be correlated to the inhibitory activity.

Antifungal Agents↗
PubMed1994

Inhibitors of ribonucleotide reductase. Comparative effects of amino- and hydroxy-substituted pyridine-2-carboxaldehyde thiosemicarbazones.

A new series of alpha-(N)-heterocyclic carboxaldehyde thiosemicarbazones (HCTs) was studied for their effects on L1210 cell growth in culture, cell cycle transit, nucleic acid biosynthesis and ribonucleotide reductase activity. 3-Aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) and 3-amino-4-methylpyridine-2-carboxaldehyde thiosemicarbazone (3-AMP) were the most active compounds tested with respect to inhibition of cell growth and ribonucleotide reductase activity. 5-Aminopyridine-2-carboxaldehyde thiosemicarbazone (5-AP) and 4-methyl-5-aminopyridine-2-carboxaldehyde thiosemicarbazone (5-AMP) were slightly less active. 3-AP, 3-AMP, 5-AP and 5-AMP inhibited the incorporation of [3H]thymidine into DNA without affecting the rate of incorporation of [3H]uridine into RNA. The uptake and incorporation of [14C]cytidine into cellular ribonucleotides and RNA, respectively, were not decreased by 3-AP or 3-AMP; however, the incorporation of cytidine into DNA via ribonucleotide reductase was inhibited markedly. Thus, a pronounced decrease in the formation of [14C]deoxyribonucleotides from radioactive cytidine occurred in the acid-soluble fraction of 3-AP- and 3-AMP-treated L1210 cells. Consistent with an inhibition of DNA replication that occurred at relatively low concentrations of 3-AP and 3-AMP, cells gradually accumulated in the S-phase of the cell cycle; at higher concentrations of 3-AP and 3-AMP, a more rapid accumulation of cells in the G0/G1 phase of the cell cycle occurred, with the loss of the S-phase population, implying that a second less sensitive metabolic lesion was created by the HCTs. N-Acetylation of 3-AMP resulted in a compound that was 10-fold less active as an inhibitor of ribonucleotide reductase activity and 8-fold less active as an inhibitor of L1210 cell growth. N-Acetylation of either 5-AP or 5-AMP did not alter the inhibitory properties of these compounds. The results obtained provide an experimental rationale for the further development of the HCTs, particularly 3-AP and 3-AMP, as potential drugs for clinical use in the treatment of cancer.

Animals↗
PubMed1995

Structure-function relationships for a new series of pyridine-2-carboxaldehyde thiosemicarbazones on ribonucleotide reductase activity and tumor cell growth in culture and in vivo.

The synthesis of a new series of pyridine-2-carboxaldehyde thiosemicarbazones (HCTs) that have amino groups in the 3- and 5-positions has allowed the comparison of the structure/function relationships with regard to inhibition of ribonucleotide reductase activity, L1210 cell growth in culture and L1210 leukemia in vivo. 3-Aminopyridine-2-carboxaldehyde thiosemicarbazones are more active than the corresponding 3-hydroxy-derivatives. The 3-amino-2-pyridine carboxaldehyde thiosemicarbazones were also more active then the 5-amino-2-carboxaldehyde thiosemicarbazones in inhibiting ribonucleotide reductase activity and L1210 cell growth in culture and in vivo. N-Acetylation of the 3-amino derivative resulted in a compound that was much less active both in vitro and in vivo; N-acetylation of the 5-amino derivative did not alter the in vitro inhibitory properties, but did eliminate the antitumor properties in vivo. When the most active HCTs were studied in more detail, it was found that the incorporation of [3H]thymidine into DNA was inhibited completely without the inhibition of [3H]uridine incorporation into RNA. Further, the conversion of [14C]cytidine to deoxycytidine nucleotides and incorporation into DNA was inhibited by the HCTs without an effect on the incorporation of cytidine into RNA. These data support the conclusion that ribonucleotide reductase is the major site of action of these HCTs. The 3-aminopyridine-2-carboxaldehyde thiosemicarbazones emerge as strong candidates for development for clinical trials in cancer patients.

Acetylation↗
PubMed2006

Cyclooctadiene Ru(II) complexes of thiophene-2-carboxaldehyde-derived thiosemicarbazones: synthesis, characterization and antiamoebic activity.

Thiosemicarbazones (TSC) 1-10 were synthesized by condensing substituted thiosemicarbazide with thiophene-2-carboxaldehyde. These thiosemicarbazones were further reacted with [Ru(eta4-C8H12)(CH3CN)2Cl2] to form complexes of the type [Ru(eta4-C8H12)(TSC)Cl2] 1a-10a. Thiosemicarbazones exhibited antiamoebic activity in the range IC50=1.09-5.42 microM. In vitro assessment of antiamoebic activity indicated that the thiosemicarbazones 3, IC50=1.67 microM, 4, IC50=1.11 microM and 6, IC50=1.09 microM showed substantially less IC50 value than metronidazole (IC50=1.87 microM), a commonly used drug against amoebiasis. Cyclooctadiene Ru(II) complexes of thiosemicarbazones showed significant improvement in antiamoebic activity (IC50=0.30-1.39 microM). All the complexes possess noteworthy potencies and showed less IC50 values than metronidazole against HK-9 strain of Entamoeba histolytica. Among all the complexes, the most promising antiamoebic activities was shown by the complexes 4a and 6a (IC50=0.31 microM of 4a and IC50=0.30 microM of 6a versus metronidazole).

Aldehydes↗