Pharmacological activities of some synthetic peptides related to dermorphin

Objectives: To investigate the relationship between the structure of demorphins (DM) and their pharmacological properties, six analogues of Hyp6DM and Pro6DM were synthesised and their biological activities were studied. Methods: The peptides were synthesised by the solid phase method using 9-fluorenylmethoxycarbonyl amino acid trichlorophenyl esters as coupling agents and Merrifield resin as solid support. The opioid agonist activity was studied using co-axially, electrically stimulated contraction of isolated guinea pig ileum (GPI, in vitro). Their analgesic activity was assessed in mice using Eddy's hot plate method and tail-flick method. The antidiarrhoeal activity was determined by the charcoal meal test in mice. Results: In the GPI assay, the synthetic analogues possess agonistic activity that are less pronounced than morphine. Peptides I and II (substitution of ser of position 7 and Gly at position 4 in Hyp6DM series respectively) possessed considerable analgesic activity but are almost inactive in the GPI assay. Peptide III (Pro6, Sar7DM) possess only analgesic activity. In GPI assay, peptide IV was inactive. Peptide V and VI had equipotent analgesic and antidiarrhoeal activity. Conclusion: Peptides with various structures can possess specificities that may prove useful in biological applications. Among them Sar4, Hyp6, Tyr7DM, Hyp6, Pro7DM, Pro6, Sar DM and Phg3, ProDM exhibited a high degree of selectivity in their activities

Solid phase synthesis of O-glycoopioid peptides related to dermorphin

Glycosylation of Fmoc-hydroxyamino acids with β-D-glucose pentaacetate has been carried out in the presence of several Lewis acids and BF3.Et2O has been found to be the most suitable one. Thus, 2,3,4,6-tetra-O-acetyl-β-D-glycopyranosyl derivatives of Fmoc-Ser/Thr/Tyr are prepared in a single step in reasonably good yields and high purity. The O-glycosylated derivatives are then converted to their corresponding trichlorophenyl esters for use in the solid phase synthesis of five glycoopioid peptides related to dermorphin. The effect of glycosylation on biological activity of dermorphin has been studied. Among the peptides synthesized, Tyr(β-D-Glc)5dermorphin and Ser(β-D-Glc)5, Tyr7)dermorphin exhibit considerable analgesic activity of about 80-90% compared to morphine and antidiarrhoeal activity of about 50% compared to dermorphin

Synthesis of peptides mediated by KOBt

Coupling of Fmoc-amino acid chlorides can be mediated by the potassium salt of 1-hydroxybenzotriazole (KOBt), the reaction being carried out in an organic medium. The use of a base like NaHCO3/Na2CO3 or DIEA/NMM/pyridine is not necessary. Coupling is fast and racemization free; the work-up, isolation of the product and scale-up are easy. The pentapeptide sequence of Fmoc-Leuenkephalin was thus synthesized in the solution phase on a 5 mmol scale without isolation of any intermediate. Acylation of C-protected N- methylamino acid esters by Fmoc-N-methylamino acid chlorides by this procedure is also feasible, as demonstrated by the synthesis of cyclosporin A fragments 4-7 and 8-11. The peptides obtained in high yields were crystalline solids, unlike earlier reports in which they were obtained mostly as oily or foamy intermediates. They showed spectral properties identical with those of the authentic compounds

Solid-phase synthesis of oxytocin using iodotrichlorosilane as Boc deprotecting agent

Deprotection of the tert-butoxycarbonyl group during solid-phase synthesis of peptides can be conveniently and efficiently carried out using a neutral reagent, silicon tetrachloride/sodium iodide (iodotrichlorosilane). This simple and rapid method has been advantageously employed during the solid-phase synthesis of the pituitary hormone, oxytocin

Synthetic peptides related to δ-receptor agonist dermorphin gene associated peptide

Five peptides related to the δ-receptor agonist, dermorphin gene associated peptide (DGAP), having structural modifications at the positions 2, 6 and 7 were synthesised by the solid phase method using 9-fluorenylmethoxycarbonyl amino acid trichlorophenyl esters as coupling agents and p-alkoxybenzyl alcohol resin as the solid support. The biological activities of these peptides were determined in vitro using guinea pig ileum and mouse vas deferens assays and in vivo employing the analgesic and antidiarrhoeal assays. The δ-receptor selectivity was determined by the ratio of IC50 values in the MVD assay to that of the GPI assay and all the synthetic peptides were found to possess δ-receptor selectivity; Nva6DGAP being the most selective in the present series. Eth6DGAP exhibits a higher selectivity with regard to analgesic to antidiarrhoeal activity in the in vivo assay

Synthetic peptides related to laminin pentapeptide (YIGSR) fragment

The synthetic laminin pentapeptide amide fragment (LF), Tyr-Ile-Gly-Ser-Arg-NH2 corresponding to a part of B1 chain of the glycoprotein, laminin, and six of its analogues having structural modifications at positions 1, 3 and 4 were synthesized by solid phase method employing mainly 9-fluorenylmethoxycarbonyl-amino acid trichlorophenyl esters as coupling agents and Merrifield resin as the solid support. Their biological activities were studied in vivo by lung tumor colonization assay and in vitro by cell adhesion assay. The activity of synthetic LF was found to correlate with the earlier reported results in both in vivo and in vitro assays. Among the analogues made, Tyr4 LF and Thr4LF were found to inhibit the lung tumor colonies more efficiently than LF itself in the in vivo assay whereas D- Ser4LF exhibited almost the same inhibition as LF