Behavioral responses and bioefficacy of some aromatic amides against Aedes aegypti

A series of substituted aromatic amides by varying the chain length, substitution of methyl, methoxy, chloro, and fluoro groups at ortho-, meta-, and para-positions of the phenyl ring of N,N-diethyl-2-phenylacetamide were synthesized. Laboratory studies were carried out to observe the behavioral responses and repellent activity of these newly synthesized aromatic amides against Aedes aegypti (L.) mosquitoes. The deterrent activity of these synthetic amides against any vectors has not been reported previously. These aromatic amides were tested for their behavioral responses and compared with the well known insect repellents, namely, N,N-diethyl toluamide; N,N-diethyl phenylacetamide; and N,N-diethylbenzamide. Out of the 14 compounds synthesized, seven compounds were selected on the basis of those showing >75% of repellent response for the bioefficacy test on human volunteers. The potential use of lead compounds in personal protection management is discussed.     

Effects of piperine analogues on stimulation of melanocyte proliferation and melanocyte differentiation

A wide range of piperine analogues has been synthesised in order to undertake a structure-activity study of their ability to stimulate melanocyte proliferation. Results demonstrate that an aromatic ring containing at least one ether function and a carbonyl group containing side chain is essential for this activity. A number of highly active piperine analogues have been identified, for instance 1-(3,4-methylenedioxyphenyl)-penta-2E,4E-dienoic acid methyl ester (5a), 1-E,E-piperinoyl-isobutylamine (4f) and 1-(3,4-methylenedioxyphenyl)-pentanoic acid cyclohexyl amide (20). A selection of analogues has also been evaluated for their effect on melanocyte morphology and melanogenesis. The piperine analogues altered cell morphology by increasing dendrite formation leading to bi-, tri- and quadripolar cells. These same analogues were found to increase total melanin in cell cultures, although melanin content per cell was not significantly altered from control in the presence of these compounds.     

Design,synthesis, and pharmacological effects of structurally simple ligands for MT1 and MT2 melatonin receptors

A series of phenoxyalkyl and phenylthioalkyl amides were prepared as melatoninergic ligands. Modulation of affinity of the newly synthesized compound by applying SARs around the terminal amide moiety, the alkyl chain, and the methoxy group on the aromatic ring provides compounds with nanomolar affinity for both melatonin receptor subtypes. Affinity towards MT₁ and MT₂ receptors were modulated also exploiting chirality. The investigation of intrinsic activity revealed that all the tested compounds behave as full or partial agonists.     

Positioning of the carboxamide side chain in 11-oxo-11H-indeno[1,2-b]quinolinecarboxamide anticancer agents: effects on cytotoxicity

A series of 11-oxo-11H-indeno[1,2-b]quinolines bearing a carboxamide-linked cationic side chain at various positions on the chromophore was studied to determine structure-activity relationships between cytotoxicity and the position of the side chain. The compounds were prepared by Pfitzinger synthesis from an appropriate isatin and 1-indanone, followed by various oxidative steps, to generate the required carboxylic acids. The 4- and 6-carboxamides (with the side chain on a terminal ring, off the short axis of the chromophore) were effective cytotoxins. The dimeric 4- and 6-linked analogues were considerably more cytotoxic than the parent monomers, but had broadly similar activities. In contrast, analogues with side chains at the 8-position (on a terminal ring but off the long axis of the chromophore) or 10-position (off the short axis of the chromophore but in a central ring) were drastically less effective. The 4,10- and 6,10-biscarboxamides had activities between those of the corresponding parent monocarboxamides. The first of these showed good activity against advanced subcutaneous colon 38 tumours in mice.     

Synthesis and inhibitory effect of piperine derivates on monoamine oxidase

A series of piperine derivates (1-19) have been designed, synthesized and evaluated in vitro for their monoamine oxidase (MAO) A and B inhibitory activity and selectivity. It is worth noting that most of the small amine moieties substituted on the piperidine ring proved to be potent and selective inhibitors of MAO-B rather than of MAO-A. 5-(3,4-methylenedioxyphenyl)-2E,4E-pentadienoic acid n-propyl amide (3) showed the greatest MAO-B inhibitory activity (IC(50)(MAO-B)=0.045 μM) and good selectivity (IC(50)(MAO-A)=3.66 μM). The conjugated double bond and carbonyl group of piperine are proved to be an essential feature for piperine and related alkylamides to exhibit MAO-inhibitory activity. Binding mode of the titled compounds was predicted using FlexX algorithm. The design and optimization of novel small molecule monoamine oxidase inhibitors will be guided by the results of this report.     

Hepatoprotective amide constituents from the fruit of Piper chaba: Structural requirements,mode of action,and new amides

The 80% aqueous acetone extract from the fruit of Piper chaba (Piperaceae) was found to have hepatoprotective effects on d-galactosamine (d-GalN)/lipopolysaccharide-induced liver injury in mice. From the ethyl acetate-soluble fraction, three new amides, piperchabamides E, G, and H, 33 amides, and four aromatic constituents were isolated. Among the isolates, several amide constituents inhibited d-GalN/tumor necrosis factor-α (TNF-α)-induced death of hepatocytes, and the following structural requirements were suggested: (i) the amide moiety is essential for potent activity; and (ii) the 1,9-decadiene structure between the benzene ring and the amide moiety tended to enhance the activity. Moreover, a principal constituent, piperine, exhibited strong in vivo hepatoprotective effects at doses of 5 and 10 mg/kg, po and its mode of action was suggested to depend on the reduced sensitivity of hepatocytes to TNF-α.     

Novel aromatic ester from Piper longum and its analogues inhibit expression of cell adhesion molecules on endothelial cells

We report here the isolation and characterization of two active principles, ethyl 3',4',5'-trimethoxycinnamate (1) and piperine (2), from the combined hexane and chloroform extracts of Piper longum. Using primary human umbilical vein endothelial cells, we evaluated the activities of compound 1 on TNF-alpha-induced expression of cell adhesion molecules, viz., ICAM-1, VCAM-1, and E-selectin, which play key roles in controlling various inflammatory diseases. Both compounds 1 and 2 inhibited the TNF-alpha-induced expression of ICAM-1 in a dose- and time-dependent manner; however, the activity of ethyl 3',4',5'-trimethoxycinnamate (1) was approximately 1.3 times higher than that of piperine (2). As ethyl 3',4',5'-trimethoxycinnamate (1) has been isolated for the first time from a natural source, Piper longum, and it exhibited higher activity, we carried out further studies on it. To correlate its cell adhesion molecule inhibitory activity with its functional consequences, we showed that it significantly blocked the adhesion of neutrophils to endothelium in a time- and concentration-dependent manner. Importantly, the inhibitory effect of cinnamate 1 was found to be reversible. To elucidate its structure-function-activity relationship, we synthesized nine different analogues of ethyl 3',4',5'-trimethoxycinnamate, i.e., compounds 3-11, and compared the ICAM-1 inhibitory activity of compound 1 with those of its synthetic analogues as well as the corresponding acids 12-15. The structure-activity studies indicate that the chain length of the alcohol moiety, substituents in the aromatic ring, and alpha, beta-double bond of the cinnamic acid ester have significant effects on the inhibition of TNF-alpha-induced expression of ICAM-1 on endothelial cells. These findings have implications in developing compounds with a better therapeutic index against various inflammatory diseases.     

Design, synthesis and nootropic activity of new analogues of sunifiram and sapunifiram, two potent cognition-enhancers

A series of amides and sulfonamides, structurally related to DM235 (sunifiram) and MN19 (sapunifiram), derived by ring expansion or contraction, or by inversion of the exocyclic amide function, have been synthesized and tested for cognition-enhancing activity in the mouse passive-avoidance test. Some of the compounds display good antiamnesic and procognitive activity, with higher potency than piracetam, and with a potency similar to the parent compounds.     

Citral derived amides as potent bacterial NorA efflux pump inhibitors

Monoterpene citral and citronellal have been used as starting material for the preparation of 5,9-dimethyl-deca-2,4,8-trienoic acid amides and 9-formyl-5-methyl-deca-2,4,8-trienoic acid amides. The amides on bioevaluation as efflux pump inhibitors (EPIs) against Staphylococcus aureus 1199 and NorA overexpressing S. aureus 1199B bacteria resulted in the identification of several of these as potent EPIs. Many of these amides have been shown to possess potency higher or equivalent to known EPIs such as reserpine, verapamil, carsonic acid, and piperine. In this communication, we report a convenient synthesis of alkenyl amides, their bioevaluation and identification as efflux pump inhibitors against S. aureus.     

Antifungal, cytotoxic and SAR studies of a series of N-alkyl, N-aryl and N-alkylphenyl-1,4-pyrrolediones and related compounds

The synthesis, in vitro evaluation and SAR studies of 67 maleimides and derivatives acting as antifungal agents are reported. A detailed SAR study supported by theoretical calculations led us to determine that: an intact maleimido ring appears to be necessary for a strong antifungal activity, dissimilarly affected by the substituents in positions 2 and 3. The best activities were shown by 2,3-nonsubstituted followed by 2,3 dichloro- and 2-methyl-substituted maleimides. They all were fungicide rather than fungistatic enhancing the importance of their antifungal activity. 2,3-Dimethyl and 2,3-diphenyl-maleimides possessed marginal or null activity. The presence of a flexible connecting chain in N-phenylalkyl maleimides appears not to be essential for antifungal activity, although its length shows a correlation with the antifungal behavior, displaying maleimides with alkyl chains of n=3 and n=4 the best antifungal activities in most fungi. Different substituents on the benzene ring did not have a clear influence on the activity. Values of chemical potential properties as well as of energy do not sufficiently discriminate between active and inactive compounds. Nevertheless, it was found that, although logP alone is not strong enough to properly predict the antifungal activity, the comparison of its values for compounds within the same sub-type, showed an enhancement of antifungal activity along with an increment of lipophilicity. In addition, the LUMO's electronic clouds of the highly active compounds showed to be concentrated on the imido ring, indicating that their carbon atoms are potential sites for nucleophilic attack. Same results were obtained from MEPs. Most of the active compounds did not show cytotoxic activity against human cancer cell lines and no one possessed hemolytic activity, indicating that their activity is selective to pathogenic fungi and that they are not toxic at MIC concentrations.     

Studies on the chemistry of thienoanellated O,N- and S,N-containing heterocycles. Part 30: synthesis and pharmacological properties of thieno[2,3-b][1,4]thiazines with potential vasopressin receptor antagonistic activity

A series of new nonpeptide vasopressin antagonists with a 6-ethyl-thieno[2,3-b][1,4]thiazine or 6-benzyl-thieno[2,3-b][1,4]thiazine skeleton and structural modifications of the aryl side chain were synthesized in this study. The effects on guinea pig heart and smooth muscle preparations were investigated. In the presence of AVP the compounds showed an antagonistic effect. The compounds did not change spontaneous rate in right atria and exerted a slight but not significant negative inotropic effect in papillary muscles. The relaxing effect on vascular smooth muscle and terminal ileum was far more pronounced. Generally the relaxing effect on terminal ilea was more potent maybe due to difference in V1a receptor density. Our results demonstrate that compounds with an ethyl group in position six on the thienothiazine ring (14, 16, 18 and 22) exerted the most potent relaxing activity in terminal ilea, whereas compounds with a phenyl ring in position six reduced this effect.     

Piperine analogs as potent Staphylococcus aureus NorA efflux pump inhibitors

Based on our recent findings that piperine is a potent Staphylococcus aureus NorA efflux pump inhibitor (EPI), 38 piperine analogs were synthesized and bioevaluated for their EPI activity. Twenty-five of them were found active with potentiating activity equivalent or more than known EPIs like reserpine, carsonic acid and verapamil. The inhibitory mechanism of the compounds was confirmed by efflux inhibition assay using ethidium bromide as NorA substrate. The present communication describes the synthesis, bioevaluation and structure related activity of these efflux pump inhibitors.     

Effects of piperine on enzyme activities and bioenergetic functions in isolated rat liver mitochondria and hepatocytes

The influence of piperine on the enzymes and bioenergetic functions in isolated rat liver mitochondria and hepatocytes was studied. Piperine at lower concentrations (<50 μM) did not affect the RCR and ADP:O ratios, state 4 and 3 respirations supported by site-specific substrates, viz. glutamate + malate, succinate, and ascorbate + TMPD. The site-specific effects became significantly apparent only at higher concentrations. Only the state 3 respiration supported by NAD-linked substrates was impaired equipotently in mitochondria and permeabilized hepatocytes; the effect appeared to be localized at energy-coupling site 1. In hypotonic treated mitochondria, respiration supported by three kinds of substrates was not affected. Among the respiratory chain-linked enzymes, the activity of NADH-dehydrogenase registered a significant decrease of about 25, 42, and 53% at 100, 150, and 180 μM piperine, respectively. The activity of Mg⁺⁺-ATPase, however, was stimulated at concentrations above 150 μM. Among the matrix enzymes, only malate and succinate dehydrogen-ases were studied. Malate dehydrogenase only showed a strong concentration-related inhibition in both the forward and backward directions. Enzyme kinetics indicated noncompetitive inhibition with a very low Ki of 10 μM. The presence of unsaturated double bonds in the side chain of piperine appeared essential for producing this strong inhibition. The studies suggested that piperine produces concentration related site-specific effects on mitochondrial bioenergetics and enzymes of energy metabolism.     

Induction of adiponectin by natural and synthetic phenolamides in mouse and human preadipocytes and its enhancement by docosahexaenoic acid

Adiponectin, the adipose-derived cytokine, plays an important role in preventing metabolic syndromes. To develop new adiponectin inducers, eight species of ferulic esters and amides, and five related compounds were synthesized and tested on the stimulation of adiponectin production in mouse 3T3-L1 and normal human preadipocytes. The ferulamides with an aromatic ring in the N-substituent are very active in inducing adiponectin as compared with the known active compounds, curcumin, [6]-gingerol, and capsaicin, and furthermore the activities of these ferulamides are remarkably stronger than those of the corresponding esters or the straight chain octylamide. The most active compound, N-(2-phenylethyl)ferulamide (7), was found to activate the PPAR (peroxisome proliferator-activated receptor) gamma-RXR (retinoid X receptor) alpha heterodimeric complex in the PPRE (PPAR-responsive element)-driven luciferase reporter assay. The adiponectin production by 7 is synergistically enhanced by coaddition of a PPARgamma-specific agonist, pioglitazone (PGZ), or another PPARgamma agonist, docosahexaenoic acid (DHA), in cultured preadipocytes. The compound 7 alone did not show a statistically significant effect on the plasma adiponectin level in KK-A(y)/Ta mice, while 1% 7 in the diets significantly lowered the blood glucose and triglyceride levels and 0.3% 7 mixed with DHA oil in the diets significantly increased the adiponectin level as compared with the control. These results suggest that the present ferulamides would be useful lead compounds in developing more potent agents for treatment of metabolic syndromes through promoting the endogenous adiponectin production, and that such an activity is possibly enhanced by the coadministration with DHA.     

Influence of curcumin, capsaicin, and piperine on the rat liver drug-metabolizing enzyme system in vivo and in vitro

The effect of dietary supplementation of spice-active principles, curcumin (0.2%), capsaicin (0.015%), and piperine (0.02%) on the activities of the liver drug-metabolizing enzyme system was examined. All the 3 dietary spice principles significantly stimulated the activity of aryl hydroxylase. A synergistic action of dietary curcumin and capsaicin with respect to stimulating the activity of aryl hydroxylase was also evidenced when fed in combination. The activity of N-demethylase essentially remained unaffected by dietary curcumin, capsaicin, or their combination, but was significantly lowered as a result of piperine feeding. Uridine dinucleotide phosphate (UDP)-glucuronyl transferase activity was decreased by dietary piperine and the combination of curcumin and capsaicin. NADPH-cytochrome c reductase activity was significantly decreased by dietary piperine. The levels of hepatic microsomal cytochrome P450 and cytochrome b5 were not influenced by any of the dietary spice-active principles. These spice-active principles were also examined for their possible in vitro influence on the components of the hepatic drug-metabolizing enzyme system in rat liver microsomal preparation. Piperine significantly decreased the activity of liver microsomal aryl hydroxylase activity when included in the assay medium at 1 x 10(-6) mol/L, 1 x 10(-5) mol/L, and 1x 10(-4) mol/L level. Lowered activity of N-demethylase was observed in presence of capsaicin or piperine at 1 x 10(-6) mol/L in the assay medium. Hepatic microsomal glucuronyl transferase activity was significantly decreased in vitro by addition of capsaicin or piperine. Capsaicin and piperine brought about significant decrease in liver microsomal cytochrome P450 when included at 1 x 10(-6) mol/L and 1 x 10(-5) mol/L, the effect being much higher in the case of piperine. The results suggested that whereas the 3 spice principles have considerable similarity in structure, piperine is exceptional in its influence on the liver drug-metabolizing enzyme system. The study also indicated that a combination of curcumin and capsaicin does not produce any significant additive effect on the liver drug-metabolizing enzyme system.     

Piperine,a dietary phytochemical,inhibits angiogenesis

Angiogenesis plays an important role in tumor progression. Piperine, a major alkaloid constituent of black pepper, has diverse physiological actions including killing of cancer cells; however, the effect of piperine on angiogenesis is not known. Here we show that piperine inhibited the proliferation and G₁/S transition of human umbilical vein endothelial cells (HUVECs) without causing cell death. Piperine also inhibited HUVEC migration and tubule formation in vitro, as well as collagen-induced angiogenic activity by rat aorta explants and breast cancer cell-induced angiogenesis in chick embryos. Although piperine binds to and activates the cation channel transient receptor potential vanilloid 1 (TRPV1), its effects on endothelial cells did not involve TRPV1 since the antiproliferative effect of piperine was not affected by TRPV1-selective antagonists, nor did HUVECs express detectable TRPV1 mRNA. Importantly, piperine inhibited phosphorylation of Ser 473 and Thr 308 residues of Akt (protein kinase B), which is a key regulator of endothelial cell function and angiogenesis. Consistent with Akt inhibition as the basis of piperine's action on HUVECs, inhibition of the phosphoinositide-3 kinase/Akt signaling pathway with LY-294002 also inhibited HUVEC proliferation and collagen-induced angiogenesis. Taken together, these data support the further investigation of piperine as an angiogenesis inhibitor for use in cancer treatment.     

Structural components necessary for the antiestrogenic activity of tamoxifen

The biological activities of tamoxifen derivatives that contain various side chain alterations were studied using a T47D breast cancer cell growth assay in vitro. We studied the activity of various analogs to determine the important aspects of side chain composition and aryl ring positioning on antiestrogenic activity. Previous studies utilizing a rat pituitary cell prolactin synthesis assay have shown that substitution of the aminoethoxy side chain for an allyl side chain resulted in agonist activity, whereas the addition of a glyceryl side chain produced antiestrogenic activity. In the present study utilizing T47D cells, compounds with alkyl or allyl substitutions were partial agonists, as were compounds with bulky para-substituted benzyl group constituents. A tamoxifen derivative with a side chain containing an ethyl ester was antiestrogenic (IC50 = 2 x 10(-6) M) and effectively inhibited estradiol (10(-10) M) stimulation of growth. However, a compound with a short similar methyl ester-containing side chain did not possess any activity. Compounds with carbinol-containing side chains were antiestrogenic (IC50 = 2.8-3.5 x 10(-7) M). All of the compounds displaying antiestrogenic activity could be "rescued" by incubation with estradiol (10(-8) M) and therefore were not nonspecifically toxic to the cells. These results support the hypothesis that the presence of a lone pair of electrons within the side chain region of tamoxifen may be required for antiestrogenic activity. Also, nonplanar placement of the aryl ring of the triphenylethylene-type of compound is critical for potency.     

Piperine,a Natural Bioenhancer,Nullifies the Antidiabetic and Antioxidant Activities of Curcumin in Streptozotocin-Diabetic Rats

Knowing that curcumin has low bioavailability when administered orally, and that piperine has bioenhancer activity by inhibition of hepatic and intestinal biotransformation processes, the aim of this study was to investigate the antidiabetic and antioxidant activities of curcumin (90 mg/kg) and piperine (20 or 40 mg/kg), alone or co-administered, incorporated in yoghurt, in streptozotocin (STZ)-diabetic rats. The treatment for 45 days of STZ-diabetic rats with curcumin-enriched yoghurt improved all parameters altered in this experimental model of diabetes: the body weight was increased in association with the weight of skeletal muscles and white adipose tissues; the progressive increase in the glycemia levels was avoided, as well as in the glycosuria, urinary urea, dyslipidemia, and markers of liver (alanine and aspartate aminotransferases and alkaline phosphatase) and kidney (urinary protein) dysfunction; the hepatic oxidative stress was decreased, since the activities of the antioxidant enzymes superoxide dismutase, catalase and gluthatione peroxidase were increased, and the levels of malondialdehyde and protein carbonyl groups were reduced. The dose of 20 mg/kg piperine also showed antidiabetic and antioxidant activities. The treatment of STZ-diabetic rats with both curcumin and 20 mg/kg piperine in yoghurt did not change the antidiabetic and antioxidant activities of curcumin; notably, the treatment with both curcumin and 40 mg/kg piperine abrogated the beneficial effects of curcumin. In addition, the alanine aminotransferase levels were further increased in diabetic rats treated with curcumin and 40 mg/kg piperine in comparison with untreated diabetic rats. These findings support that the co-administration of curcumin with a bioenhancer did not bring any advantage to the curcumin effects, at least about the antidiabetic and antioxidant activities, which could be related to changes on its biotransformation.     

Investigation into new anticonvulsant derivatives of alpha-substituted N-benzylamides of gamma-hydroxy- and gamma-acetoxybutyric acid. Part 5: search for new anticonvulsant compounds

A series of four N-benzylamides of gamma-hydroxybutyric acid (GHB), that contain N-(4-phenylpiperazine)-, N-(4-benzylpiperazine)rings, N-benzylamino-, or N-(2-phenylethylamine)-groups in the alpha-position of GHB were selected as model compounds, for determining the structural elements responsible for their potential anticonvulsant action. Based on the results of pharmacological, physicochemical, and molecular modelling investigations, the pharmacophore model for anticonvulsant N-substituted amides of GHB was defined. In this model, the presence of the N-benzylamide fragment is essential for activity. In addition, all of the amides contained another hydrophobic unit (aryl ring) as a distal binding site and H-bond donor. In consideration of these model parameters, a number of N-substituted amides of GHB, containing a hydrophobic moiety such as: N-benzylamino or N-(4-chlorobenzylamino) group in the alpha-position of GHB, and a lipophilic substituent in the amide portion, were prepared. It has been shown that the anticonvulsant activities of the newly synthesized compounds might partially be explained on the basis of their lipophilicity (calculated log P values) and the presence of a hydroxyl group in the molecule.