Analogues of a potent oxytocin antagonist with truncated C-terminus or shorter amino acid side chain of the basic amino acid at position 8.

Twelve analogues were synthesized, their structure derived from modifications of [(S)Pmp1, D-Trp2, Pen6, Arg8]oxytocin, PA, in which (S)Pmp = beta,beta-(3-thiapentamethylene-beta-mercaptopropionic acid). PA is a potent antagonist of the uterotonic effect of oxytocin in the rat (uterotonic test in vitro, pA2 = 8.86) and in the baboon. Truncated analogues of PA from the C-terminus were systematically prepared ending in either the free acid or the amide, i.e. PA1-9 acid, PA1-8 acid, PA1-7 acid, PA1-6 acid, PA1-8 amide, PA1-7 amide and PA1-6 amide. PA1-8 amide was roughly as potent as PA in the rat uterotonic assay in vitro, and the shorter amides were only somewhat weaker antagonists. All four acid analogues were weaker antagonists than PA but still maintained rather high antagonistic potency. These findings suggest that, if these truncated acids form as metabolites in vivo, they may contribute to the overall biological effect of PA and their contribution should be taken into account. Furthermore, using these analogues, the radioimmunoassay measurements of PA may be standardized, as they may cross react with PA antibodies and interfere with the determination. In addition, five analogues were made by substituting Arg8 of PA with Lys, Orn8, Dab8, Dap8 and Cit8. All of these analogues maintained high potency as OTAs in the uterotonic assay, although their activity was only about 1.5-3 times lower than PA. The most potent analogue in the uterotonic assay, [Dap8]PA, pA2 = 8.53, had weak pressor activity (pA2 = 6.90) and no antidiuretic effect. The pressor activity was lower for all tested acids, and for PA1-6 acid it was even below the detection limit. Additionally, PA1-9 acid, PA1-7 acid and PA1-6 acid showed no antidiuretic activity. Hence, the PA1-6 acid is a potent OTA with pA2 = 8.27 and no measurable effect in the pressor or antidiuretic tests and thus it is a pure oxytocin antagonist. This fact makes it an attractive candidate for further studies on inhibition of OT biological effects and on preterm labour.     

Effects of bPTH fragments (1-34), (3-34) and (7-34) on uterine contraction

Synthetic bovine parathyroid hormone containing the NH2 terminal 34 amino acids [bPTH-(1-34)] was recently demonstrated to inhibit oxytocin stimulated uterine contraction in vitro. The parathyroid hormone analogues [Nle8, Nle18, Tyr34]bPTH-(3-34)amide [NTA-(3-34)] and [Tyr34]bPTH-(7-34)amide [NTA-(7-34)] have been reported to act as inhibitors of antagonists of parathyroid hormone (PTH) in numerous assays. In the present study the effects of these PTH analogues on uterine contraction and the ability of these analogues to act as antagonists to the uterine inhibitory action of bPTH-(1-34) in vitro were investigated. The NTA-(3-34) fragment had no effect on oxytocin stimulated uterine contractions. However, the NTA-(3-34) fragment was able to alter the ability of bPTH (1-34) to reduce oxytocin stimulated uterine contraction in a dose-related manner. Bovine PTH(1-34) (0.3 microgram/ml) reduced the contractile response obtained with oxytocin (0.5 mU/ml) by 20%. A dose of 15 micrograms/ml) of NTA-(3-34) abolished this inhibitory action of bPTH-(1-34) on oxytocin stimulated uterine contraction. In contrast the NTA-(7-34) caused a change in itself, stimulated contraction of resting uterine horns in a dose-related manner; 3.0 micrograms/ml of NTA-(7-34) caused a change in gram tension of + 1.5 grams. Bovine PTH-(1-34) was able to reduce the uterine contraction stimulated by NTA-(7-34) and 0.3 microgram/ml of bPTH-(1-34) reduced the contractile response obtained with 3.0 micrograms/ml of NTA-(7-34) by as much as 70%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and antibacterial activity of hydrolytically stable (-)-epicatechin gallate analogues for the modulation of beta-lactam resistance in Staphylococcus aureus

Hydrolytically more stable analogues of (-)-epicatechin gallate (ECg) have been synthesised from ECg where an amine or amide function has been substituted for the ester linkage that joins the C-ring with the galloyl D-ring. Sub-inhibitory concentrations (25 mg/L) of the amide analogue 7, possessing the natural C-3 stereochemistry, were able to reduce the resistance to oxacillin of three strains of methicillin resistant Staphylococcus aureus (BB 568, EMRSA-15 and EMRSA-16) comparable to levels achieved with ECg.     

Iso-lactam and reduced amide analogues of the peptidomimetic dopamine receptor modulator 3(R)-[(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide

An analogue of the highly potent gamma-lactam Pro-Leu-Gly-NH(2) peptidomimetic, 3(R)-[(2(S)-pyrrolidinylcarbonyl) amino]-2-oxo-1-pyrrolidineacetamide (2), 4(R)-[[2(S)-pyrrolidinylcarbonyl]amino]-2-oxo-1-pyrrolidineacetamide (3), in which the lactam carbonyl moiety has been placed in a different position with respect to the 3-amino group was synthesized. Also, a series of analogues of 2, compounds 4-6, were synthesized in which each of the amide bonds of 2 were systematically replaced with a reduced amide bond surrogate. The analogues were tested for their ability to enhance the binding of [3H]N-propylnorapomorphine to dopamine receptors in a functional in vitro assay utilizing bovine striatal membranes. Peptidomimetic 3 was shown to be more potent than 2, while 4 and 5 were significantly less effective than 2. Peptidomimetic 6 had a pharmacological profile similar to that of 2.     

Conformationally constrained analogues of 2-arachidonoylglycerol

Novel monocyclic analogues of 2-arachidonoylglycerol (2-AG) were designed in order to explore the pharmacophoric conformations of this endocannabinoid ligand at the key cannabinergic proteins. All 2-arachidonoyl esters of 1,2,3-cyclohexanetriol [meso-7 (AM5504), (+/-)-8 (AM5503), and meso-9 (AM5505)] were synthesized by regioselective acylation of 2,3-dihydroxycyclohexanone followed by selective reductions. The optically active isomers (+)-8 (AM4434) and (-)-8 (AM4435) were synthesized from (2S,3S)- and (2R,3R)-2,3-dihydroxycyclohexanone, respectively, via a chemoenzymatic route. These head group constrained and conformationally restricted analogues of 2-AG as well as the 1-keto precursors were evaluated as substrates for the endocannabinoid deactivating hydrolytic enzymes monoacylglycerol lipase (MGL) and fatty acid amide hydrolase (FAAH), and also were tested for their affinities for CB1 and CB2 cannabinoid receptors. The observed biochemical differences between these ligands can help define the conformational requirements for 2-AG activity at each of the above endocannabinoid protein targets.     

The interaction of phospholipase A2 with phospholipid analogues and inhibitors

A series of structurally modified phospholipids have been used to delineate the structural features involved in the interaction between cobra venom (Naja naja naja) phospholipase A2 and its substrate. Special emphasis has been placed on sn-2 amide analogues of the phospholipids. These studies have led to a very potent, reversible phospholipase A2 inhibitor. A six-step synthesis of this compound, 1-palmitylthio-2-palmitoylamino-1,2-dideoxy-sn-glycero-3- phosphorylethanolamine (thioether amide-PE), was developed. Other analogues studied included 1-palmitylthio-2-palmitoylamino-1,2-dideox-sn- glycero-3-phosphorylcholine, 1-palmityl-2-palmitoylamino-2- deoxy-sn-glycero-3-phosphorylcholine, 1-palmitoyl-2-palmitoylamino-2-deoxy-sn-glycero-3- phosphorylcholine, 1-palmitylthio- 2([(tetradecyloxy)carbonyl]amino)-1,2-dideoxy-sn-glycero-3- phosphorylcholine, 1-palmitoyl- 2([(octadecylylamino)carbonyl]amino)-2-deoxy-sn-glycero-3- phosphorylcholine, and sphingomyelin. Inhibition studies used the well defined Triton X-100 mixed micelle system and the spectroscopic thio assay. The phospholipid analogues showed varying degrees of inhibition. The best inhibitor was the thioether amide-PE which had an IC50 of 0.45 microM. In contrast, sphingomyelin, a natural phospholipid that resembles the amide analogues, did not inhibit but rather activated phosphatidylcholine hydrolysis. This systematic study of phospholipase A2 inhibition led to the following conclusions about phospholipid-phospholipase A2 interactions: (i) sn-2 amide analogues bind tighter than natural phospholipids, presumably because the amide forms a hydrogen bond with the water molecule in the enzyme active site, stabilizing its binding. (ii) Inhibitor analogues containing the ethanolamine polar head group appear to be more potent inhibitors than those containing the choline group. This difference in potency may be due solely to the fact that the cobra venom phospholipase A2 is activated by choline-containing phospholipids. Thus, choline-containing non-hydrolyzable analogues both inhibit and activate this enzyme. Both of these effects must be taken into account when studying phosphatidylcholine inhibitors of the cobra venom enzyme. (iii) The potency of inhibition of these analogues is significantly enhanced by increasing the hydrophobicity of the sn-1 functional group.(ABSTRACT TRUNCATED AT 400 WORDS)     

Selective L-nitroargininylaminopyrrolidine and L-nitroargininylaminopiperidine neuronal nitric oxide synthase inhibitors

Selective inhibition of the localized excess production of NO by neuronal nitric oxide synthase (nNOS) has been targeted as a potential means of treating various neurological disorders. Based on observations from the X-ray crystal structures of complexes of nNOS with two nNOS-selective inhibitors, (4S)-N-{4-amino-5-[(2-amino)ethylamino]pentyl}-N'-nitroguanidine (L-Arg(NO2)-L-Dbu-NH2 (1) and 4-N-(Nomega-nitro-L-argininyl)-trans-4-amino-L-proline amide (2), a series of descarboxamide analogues was designed and synthesized (3-7). The most potent compound was aminopyrrolidine analogue 3, which exhibited better potency and selectivity for nNOS than parent compound 2. In addition, 3 provided higher lipophilicity and a lower molecular weight than 2, therefore having better physicochemical properties. Nalpha-Methylated analogues (8-11) also were prepared for increased lipophilicity of the inhibitors, but they had 4- to 5-fold weaker binding affinity compared to their parent compounds.     

Role of Asn(2) and Glu(7) residues in the oxidative folding and on the conformation of the N-terminal loop of apamin

The X-ray structure of [N-acetyl]-apamin has been solved at 0.95 A resolution. It consists of an 1-7 N-terminal loop stabilized by an Asn-beta-turn motif (2-5 residues) and a helical structure spanning the 9-18 residues tightly linked together by two disulfide bonds. However, neither this accurate X-ray nor the available solution structures allowed us to rationally explain the unusual downfield shifts observed for the Asn(2) and Glu(7) amide signals upon Glu(7) carboxylic group ionization. Thus, apamin and its [N-acetyl], [Glu(7)Gln], [Glu(7)Asp], and [Asn(2)Abu] analogues and submitted to NMR structural studies as a function of pH. We first demonstrated that the Glu(7) carboxylate group is responsible for the large downfield shifts of the Asn(2) and Glu(7) amide signals. Then, molecular dynamics (MD) simulations suggested unexpected interactions between the carboxylate group and the Asn(2) and Glu(7) amide protons as well as the N-terminal alpha-amino group, through subtle conformational changes that do not alter the global fold of apamin. In addition, a structural study of the [Asn(2)Abu] analogue, revealed an essential role of Asn(2) in the beta-turn stability and the cis/trans isomerization of the Ala(5)-Pro(6) amide bond. Interestingly, this proline isomerization was shown to also depend on the ionization state of the Glu(7) carboxyl group. However, neither destabilization of the beta-turn nor proline isomerization drastically altered the helical structure that contains the residues essential for binding. Altogether, the Asn(2) and Glu(7) residues appeared essential for the N-terminal loop conformation and thus for the selective formation of the native disulfide bonds but not for the activity.     

Site-directed affinity-labeling of delta opioid receptors by

The S-3-nitro-2-pyridinesulfenyl (SNpys) group in an affinity ligand can bind to a free thiol group of a cysteine residue in a target receptor molecule, forming a disulfide bond via the thiol-disulfide exchange reaction. SNpys-containing Leu-enkephalin analogues of [-Ala², Leu⁵]-enkephalyl-Cys(Npys)⁶ and [-Ala²,Leu(CH₂SNpys)⁵]enkephalin, and dynorphin A analogues of [-Ala²,Cys(Npys)¹²]dynorphin A-(1-13) amide and [-Ala²,Cys(Npys)⁸]dynorphin A-(1-9) amide have been found to affinity-label all of the δ, μ (rat brain), and κ (guinea pig brain) opioid receptor subtypes. In this study, using these chemically synthesized SNpys-containing analogues, we attempted to identify the analogues that affinity-label the cysteine residue at position 60 of the δ opioid receptor. We first established the assay procedure, principally based on the receptor binding assay to use COS-7 cells expressing the δ opioid receptor. Then, using a mutant δ receptor with the Cys60→Ala substitution, we assayed the SNpys-containing analogues for their specific affinity-labeling. [-Ala²,Cys(Npys)¹²]dynorphin A-(1-13) amide was found to have drastically reduced labeling activity for this mutant receptor as compared to its activity for the wild-type δ receptor. Other analogues exhibited almost the same activity for both the wild-type and mutant δ receptors. These results indicate that the δ-Cys60 residue has a free thiol group, which is labeled by [-Ala²,Cys(Npys)¹²]dynorphin A-(1-13) amide.     

N-acetyl-GLP-1: a DPP IV-resistant analogue of glucagon-like peptide-1 (GLP-1) with improved effects on pancreatic beta-cell-associated gene expression

Glucagon-like peptide-1(7-36)amide (GLP-1) is a key insulinotropic hormone with the reported potential to differentiate non-insulin secreting cells into insulin-secreting cells. The short biological half-life of GLP-1 after cleavage by dipeptidylpeptidase IV (DPP IV) to GLP-1(9-36)amide is a major therapeutic drawback. Several GLP-1 analogues have been developed with improved stability and insulinotropic action. In this study, the N-terminally modified GLP-1 analogue, N-acetyl-GLP-1, was shown to be completely resistant to DPP IV, unlike native GLP-1, which was rapidly degraded. Furthermore, culture of pancreatic ductal ARIP cells for 72 h with N-acetyl-GLP-1 indicated a greater ability to induce pancreatic beta-cell-associated gene expression, including insulin and glucokinase. Further investigation of the effects of stable GLP-1 analogues on beta-cell differentiation is required to assess their potential in diabetic therapy.     

Structural requirement for the agonist activity of the TLR2 ligand Pam2Cys

Synthetic lipopeptides have demonstrated great potential as a vaccine strategy for eliciting cellular and humoral immunity. One of the most potent lipid moieties used is S-[2,3-bis(palmitoyloxy)propyl]cysteine (Pam2Cys). Pam2Cys binds to and activates dendritic cells by engagement of Toll like receptor 2 (TLR 2). In this study, we have investigated the structural requirement of the agonist activity of Pam2Cys by varying the three structural elements of the core structure S-(2,3-dihydroxypropyl)-cysteine namely (1) the α-amino group of the cysteine residue (2) the sulphur atom of the cysteine residue and (3) the 2,3-dihydroxypropyl moiety. Four novel analogues of Pam2Cys were made and each of these analogues were incorporated into vaccine constructs and examined for immunogenicity. Our results demonstrate that (1) the potency of the peptide vaccine is least affected by removal of the amino group (2) substitution of the sulphur atom with an amide bond leads to significant reduction of biological activity (3) removal of the amino group and at the same time substitution of the sulphur with an amide bond significantly decreases the biological activity (4) in the two analogues in which the sulphur atom is replaced with an amide bond the analogue containing the 1,3-dihydroxypropyl moiety demonstrates higher activity than the one which contains 2,3-dihydroxypropyl. In conclusion, the results demonstrate strict structural requirements for agonist activity of the TLR2 ligand Pam2Cys.     

Neurite outgrowth-stimulating activities of beta-casomorphins in Neuro-2a mouse neuroblastoma cells

Endogenous opioid peptides and opiate drugs are known to affect the development of the nervous system. beta-Casomorphins (beta-CMs) belong to a family of exogenous opioid peptides derived from the milk protein beta-casein by proteolytic fragmentation. We investigated the effects of various fragments and analogues of beta-CM on neurite outgrowth in Neuro-2a mouse neuroblastoma cells. The fragments beta-CM-5 to -9 and beta-CM-5 amide stimulated neurite outgrowth. Fragments shorter than beta-CM-5 (beta-CM-3, -4, and beta-CM-4 amide) and longer than beta-CM-9 (beta-CM-13 and -21) had no effects. The activity of beta-CMs to promote neurite outgrowth does not correlate with their opioid activity in guinea-pig ileum. The effect of the most potent fragment, beta-CM-5, was prevented by the micro-opioid receptor-selective antagonist D-Phe-Cys(2)-Tyr(3)-D-Trp-Orn(5)-Thr(6)-Pen(7)-Thr(8)-NH(2) (CTOP), or by pretreatment with pertussis toxin. These results suggest that the stimulatory effects of beta-CMs on neurite outgrowth were mediated through G protein-coupled micro-opioid receptors.     

Potent antagonistic action of synthetic analogues of APGWGNamide,an antagonist of molluscan neuropeptide APGWamide

Fifty-five kinds of analogues of APGWGNamide (Ala-Pro-Gly-Trp-Gly-Asn-NH2), which is an antagonist of molluscan neuropeptide APGWamide, were synthesized and their antagonistic activities were examined on two molluscan smooth muscles. Among all the analogues tested, on spontaneous contraction of the crop of the land snail, Euhadra congenita, APGWG(L-biphenylalanine, Bip)amide showed the most potent antagonistic activity and its potency was 50-100 times higher than that of APGWGNamide. Likewise, on phasic contraction of the anterior byssus retractor muscle (ABRM) of the sea mussel, Mytilus edulis, the effect of APGWG(D-homophenylalanine, dHfe) was the most potent and showed 5-10 times stronger activity than that of APGWGNamide. In the tolerance test to known exo- and endopeptidases or the crop tissue homogenate, APGWGNamide was not only easily degraded by a proline-specific endopeptidase but also by the homogenate. Two kinds of potent antagonists were thus developed: APGWG(Bip)amide and APGWG(dHfe)amide, which will be useful tools for investigation of the function of APGWamide in the snail and the mussel, respectively.     

Structure activity relationship studies on the antimicrobial activity of novel edeine A and D analogues.

Edeines are pentapeptide amide antibiotics composed of four nonprotein amino acids, glycine, and polyamine. They exhibit antimicrobial and immunosuppressive activities and are universal inhibitors of translation. Moreover, it was proven that the free ionizable carboxy group in the (2R, 6S, 7R)-2,6-diamino-7-hydroxyazelaic acid moiety is not essential for biological activity of these compounds. In this paper we describe the synthesis of four novel edeine A and D analogues in which the above-mentioned acid residue was replaced with the (3R, 4S)- or (3S, 4S)-4,5-diamino-3-hydroxypentanoic acid moiety. In one compound we also introduced into molecule the 3-N,N-dimethyl derivative of (S)-2,3-diaminopropanoic acid to prevent the transpeptidation process, which results in the loss of biological activity of alpha-isomers of edeines. All peptides were synthesized applying the active ester and azide methods and on the basis of the coupling of suitable N-terminal tripeptides with proper C-terminal dipeptide amides. The activities of the newly obtained edeine analogues against selected strains of bacteria and fungi are also presented.     

Oxytocin analogues with amide groups substituted by tetrazole groups in position 4, 5 or 9

Eleven oxytocin analogues substituted in position 4, 5 or 9 by tetrazole analogues of amino acids were prepared using solid-phase peptide synthesis method and tested for rat uterotonic in vitro and pressor activities, as well as for their affinity to human oxytocin receptor. The tetrazolic group has been used as a bioisosteric substitution of carboxylic, ester or amide groups in structure-activity relationship studies of biologically active compounds. Replacement of the amide groups of Gln(4) and Asn(5) in oxytocin by tetrazole analogues of aspartic, glutamic and alpha-aminoadipic acids containing the tetrazole moiety in the side chains leads to analogues with decreased biological activities. Oxytocin analogues in which the glycine amide residue in position 9 was substituted by tetrazole analogues of glycine had diminished activities as well. The analysis of differences in rat uterotonic activity and in the affinity to human oxytocin receptors of analogues containing either an acidic 5-substituted tetrazolic group or a neutral 1,5- or 2,5-tetrazole nucleus makes it possible to draw some new conclusions concerning the role of the amide group of amino acids in positions 4, 5 and 9 of oxytocin for its activity. The data suggest that the interaction of the side chain of Gln(4) with the oxytocin receptor is influenced mainly by electronic effects and the hydrogen bonding capacity of the amide group. Steric effects of the side chain are minor. Substitution of Asn(5) by its tetrazole derivative gave an analogue of very low activity. The result suggests that in the interaction between the amide group of Asn(5) and the binding sites of oxytocic receptor hydrogen bonds are of less importance than the spatial requirements for this group.     

Novel adenosine A1 receptor antagonists. Synthesis and structure-activity relationships of a novel series of 3-(2-cyclohexenyl-3-oxo-2,3-dihydropyridazin-6-yl)-2-phenylpyrazolo[1,5 -a]pyridines

A novel series of 3-(2-cyclohexenyl-3-oxo-2,3-dihydropyridazin-6-yl)-2-phenylpyrazol o[1,5-a]pyridines was synthesized and evaluated for in vitro adenosine A1 and A2A receptor binding activities. Most of the cyclohexenyl derivatives (7a-e, 8a-s) were found to be potent adenosine A1 receptor antagonists. In a series of analogues of FR166124 (3a), alcohol 7c, nitrile 7e and amide derivatives (7d, 8c, 8r) were found to be more potent A1 antagonists with higher A2A/A1 selectivity than FR166124. Amongst them, 8r showed considerable water solubility (33.3 mg/mL), but lower than that of the sodium salt of FR166124 (> 200 mg/mL). Additionally, FR166124 had strong diuretic activity by both p.o. and iv administration in rats (minimum effective dose=0.1 and 0.032 mg/kg, respectively).     

Des-Met14]bombesin analogues function as small cell lung cancer bombesin receptor antagonists.

A series of bombesin (BN) analogues lacking the C-terminal methionine at the 14 position were evaluated as BN receptor antagonists. [D-Phe6]BN(6-13)amide inhibited specific 125I-GRP binding to lung cancer cell line NCI-H720 with an IC50 value of 12 nM. In contrast, [D-Phe6]BN(6-13)propylamide, butylamide and methylester were more potent with IC50 values of 3, 5 and 5 nM whereas [D-Phe6,Sta13]BN(6-13)amide was less potent with an IC50 value of 180 nM. [D-Phe6]BN(6-13)propylamide antagonized the ability of BN to elevate cytosolic Ca2+, whereas [D-Phe6]BN(6-13)butylamide was a partial agonist. In a small cell lung cancer (SCLC) growth assay, [D-Phe6]BN(6-13)propylamide inhibited colony formation. In summary, BN analogues which lack a C-terminal methionine may function as useful SCLC BN receptor antagonists.     

Structural analogues of 5-OMe-BPAT: synthesis and interactions with dopamine D2, D3, and serotonin 5-HT1A receptors.

Several structural analogues of 5-methoxy-2-[N-(2-benzamidoethyl)-N-n-propylamino]tetralin (5-OMe-BPAT, 1), a representative of a series of 2-aminotetralin-derived benzamides with potential atypical antipsychotic properties, were synthesized and evaluated for their ability to bind to dopamine D2A, D3, and serotonin 5-HT1A receptors in vitro. The structure affinity relationships revealed that the aromatic ring of the benzamide moiety of 1 contributes to the high affinities for all three receptor subtypes. Furthermore, 1 may interact with the dopamine D2 and D3 receptors through hydrogen bond formation with its carbonyl group. Investigation of the role of the amide hydrogen atom by amide N-alkylation was not conclusive, since conformational aspects may be responsible for the decreased dopaminergic affinities of the N'-alkylated analogues of 1. The effects of the amide modifications on the serotonin 5-HT1A receptor affinity were less pronounced, suggesting that the benzamidoethyl side-chain of 1 as a whole enhances the affinity for this receptor subtype probably through hydrophobic interactions with an accessory binding site. The structural requirements for the substituents at the basic nitrogen atom supported the hypothesis that the 2-aminotetralin moieties of the 2-aminotetralin-derived substituted benzamides may share the same binding sites as the 2-(N,N-di-n-propylamino)tetralins.     

Adjuvant activity of some nonpyrogenic hydrophobic analogues of muramyl dipeptide in enhancing the primary humoral and cell mediated immune responses in guinea pig model

Five muramyl dipeptide analogues synthesized by derivatization of gamma-carboxyl of D-isoglutamine residue of MDP into alkyl amides or incorporation of lysine residue at the site via epsilon-NH2 function were evaluated for immuno-adjuvant activity. Derivatization of gamma-carboxyl of D-isoglutamine into butyl, octyl and dibutyl residues stimulated delayed type of hypersensitivity (DTH) response, the maximum stimulation being observed with octyl amide. Introduction of lauryl amide residue abolished DTH response. The antibody response was impaired with all the alkyl amide analogues except for the lysyl amide derivative with which the response was higher than MDP. Correlation was observed between DTH response and macrophage migration.