In vivo structure–activity studies on the dark‐color‐inducing neurohormone of locusts

Abstract: In the 11‐residue long dark‐color‐inducing neurohormone (DCIN = [His⁷]‐corazonin), of locusts, from residue 2 to residue 11, one amino acid at each time was substituted by d ‐phenylalanine (d ‐Phe). The dark‐color‐inducing effect of these peptides was investigated in comparison with unaltered DCIN by a bioassay based on nymphs of a DCIN‐deficient albino mutant of the migratory locust, Locusta migratoria. Substitution of any single amino acid by d ‐Phe always reduced the activity, but did not abolish it completely. Maximum inactivation was obtained after substitution of Gln4, Ser6, or Trp9. The latter two residues are within the partial sequence ‐Ser‐Xxx‐Gly‐Trp‐ (Xxx = His in the DCIN) that seems to be important for the dark‐color‐inducing activity, as found also in another study (Insect Biochem. Mol. Biol. 32, 2002, 909). Gln4, however, is outside of this partial sequence. Minimal, although still considerable, inactivation occurred after substitution of Gly8, Phe3, or Asn11, despite the fact that Gly8 is within the ‐Ser‐Xxx‐Gly‐Trp‐ partial sequence. In conclusion, no single active core was found, indicating that the whole sequence of the DCIN is necessary to induce maximum darkening effect. No difference was found in the activity of the peptides in which Gly8 was substituted by d ‐Phe or by l ‐Phe. Therefore the ‐Ser‐Xxx‐Gly‐Trp‐ partial sequence does not seem to be stabilized by a type II β‐turn. Nevertheless, existence of another kind of turn that includes this partial sequence is feasible. A single unsuccessful attempt was made to discover an antagonist to the DCIN.     

3D‐QSAR,molecular docking,and ONIOM studies on the structure–activity relationships and action mechanism of nitrogen‐containing bisphosphonates

Nitrogen‐containing bisphosphonates (N‐BPs) have been used widely to treat various bone diseases by inhibiting the key enzyme farnesyl pyrophosphate synthase (FPPS) in the mevalonate pathway. Understanding the structure–activity relationships and the action mechanisms of these bisphosphonates is instructive for the design and the development of novel potent inhibitors. Here, a series of N‐BPs inhibitors of human FPPS (hFPPS) were investigated using a combination of three‐dimensional quantitative structure–activity relationship (3D‐QSAR), molecular docking, and three‐layer ONIOM studies. The constructed 3D‐QSAR model yielded a good correlation between the predicted and experimental activities. Based on the analysis of comparative molecular field analysis (CoMFA) contour maps, a series of novel N‐BPs inhibitors were designed and ten novel potent N‐BPs inhibitor candidates were screened out. Molecular docking and ONIOM (B3LYP/6‐31 + G*:PM6:Amber) calculations revealed that the inhibitors bound to the active site of hFPPS via hydrogen‐bonding interactions, hydrophobic interactions, and cation‐π interactions. Six novel N‐BPs inhibitors with better biological activities and higher lipophilicity were further screened out from ten candidates based on the calculated interaction energy. This study will facilitate the discovery of novel N‐BPs inhibitors with higher activity and selectivity.     

Anticancer activity of VmCT1 analogs against MCF‐7 cells

Antimicrobial peptides are considered promising drug candidates due to their broad range of activity. VmCT1 (Phe–Leu–Gly–Ala–Leu–Trp–Asn–Val–Ala–Lys–Ser–Val–Phe–NH₂) is an α‐helical antimicrobial peptide that was obtained from the Vaejovis mexicanus smithi scorpion venom. Some of its analogs showed to be as antimicrobial as the wild type, and they were designed for understanding the influence of physiochemical parameters on antimicrobial and hemolytic activity. Some cationic antimicrobial peptides exhibit anticancer activity so VmCT1 analogs were tested to verify the anticancer activity of this family of peptides. The analogs were synthesized, purified, characterized, and the conformational studies were performed. The anticancer activity was assessed against MCF‐7 mammary cancer cells. The results indicated that [Glu]⁷‐VmCT1‐NH₂, [Lys]³‐VmCT1‐NH₂, and [Lys]⁷‐VmCT1‐NH₂ analogs presented moderated helical tendency (0.23–0.61) and tendency of anticancer activity at 25 μmol/L in 24 hr of experiment; and [Trp]⁹‐VmCT1‐NH₂ analog that presented low helical tendency and moderated anticancer activity at 50 μmol/L. These results demonstrated that single substitutions on VmCT1 led to different physicochemical features and could assist on the understanding of anticancer activity of this peptide family.     

Structure–activity relationship of butyrate analogues on apoptosis,proliferation and histone deacetylase activity in HCT‐116 human colorectal cancer cells

1. Butyrate, a bacteria fermentative product in the colonic lumen, has been shown to produce a wide variety of biological effects in human cancer cells in vitro. However, there are pharmacological drawbacks associated with the use of butyrate therapy and there are limited published data on the structure–activity relationship of butyrate analogues in colorectal cancer cells. Previously, we determined structure–activity relationship using HT‐29 human colorectal cancer cells. However, it was viewed as important to explore similar relationships in another colorectal cancer cell line. 2. Therefore, in the present study, the in vitro structure–activity relationship of butyrate analogues was examined by investigating their effects on apoptosis, cell proliferation, histone deacetylase (HDAC) activity and lactate dehydrogenase (LDH) leakage as a measure of cell toxicity in HCT‐116 human colorectal cancer cells. 3. Of the 32 analogues tested, only 4‐benzoylbutyrate, 3‐benzo‐ylpropionate, 4‐(4‐nitrophenyl)butyrate and 3‐(4‐fluorobenzoyl)propionate exhibited comparable biological effects to butyrate. The common structural properties of the compounds of interest were to lack amino or hydroxyl substitutions at the 2‐, 3‐ and/or 4‐position of the aliphatic moiety of butyrate. 4. The present study reveals a dissociation between the induction of apoptosis, inhibition of cell proliferation, HDAC activity and LDH leakage. The results indicate differential responses of butyrate analogues in HT‐29 and HCT‐116 colorectal cancer cells.     

Non‐peptide‐based new class of platelet aggregation inhibitors: Design,synthesis, bioevaluation,SAR, and in silico studies

A series of 2‐oxo‐2‐phenylethylidene linked 2‐oxo‐benzo[1,4]oxazine analogues 17a–x and 18a–o , incorporated with a variety of electron‐withdrawing as well as electron‐donating groups at ring A and ring C, were synthesized under greener conditions in excellent yields (up to 98%). These analogues 17a–x and 18a–o were evaluated for their arachidonic acid (AA)‐induced platelet aggregation inhibitory activities in comparison with the standard reference aspirin (IC₅₀ = 21.34 ± 1.09 µg/mL). Among all the screened compounds, eight analogues, 17i , 17x , 18f , 18g , 18h , 18i , 18l , and 18o , were identified as promising platelet aggregation inhibitors as compared to aspirin. In addition, cytotoxic studies in 3T₃ fibroblast cell lines by MTT assay of the promising compounds ( 17i , 17x , 18f–18i , 18l , and 18o ) were also performed and the compounds were found to be non‐toxic in nature. Furthermore, the results on the AA‐induced platelet aggregation inhibitory activities of these compounds ( 17i , 17x , 18f–18i , 18l , and 18o ) were validated via in silico molecular docking simulation studies. To the best of our knowledge, this is the first report of the identification of non‐peptide‐based functionalized 2‐oxo‐benzo[1,4]oxazines as platelet aggregation inhibitors.

     

Structure–activity relationship of [Nphe1]‐NC‐(1‐13)‐NH2, a pure and selective nociceptin/orphanin FQ receptor antagonist

Abstract: A series of analogs of the ORL1 receptor antagonist [Nphe¹]‐NC(1‐13)‐NH₂ was prepared and tested for agonistic and antagonistic activities in the mouse vas deferens, a preparation that shows high sensitivity to nociceptin and related peptides. The purpose of this study was to determine the role of the aromatic residue at the N‐terminal for antagonism and eventually identify compounds with improved potency. Results indicated that all 23 compounds are inactive as agonists, and the antagonistic potency of the initial template [Nphe¹]‐NC(1‐13)‐NH₂ is high (pK_B 6.43) compared with those of all other compounds except [(S)(βMe)Nphe¹]NC(1‐13)‐NH₂ (pK_B 6.48). The other 22 compounds can be divided into two groups: 10 show antagonistic potencies (pK_B) ranging from 5.30 to 5.86, whereas the other 12 compounds are inactive. This study clearly shows that the aromatic ring of Nphe is very critical for the interaction with the ORL1 receptor and can not be enlarged or sterically modified without significant loss of antagonistic potency.     

Multiobjective Optimization on Antiplatelet Effects of Three Components Combination by Quantitative Composition–activity Relationship Modeling and Weighted‐Sum Method

Multicomponent therapeutic has become an increasingly favored strategy for treating complex diseases in recent years. In this study, a multiple objective optimization approach was proposed to design the optimal combination of three components for antiplatelet activity. The platelet aggregation assays induced by three different ways, adenosine diphosphate, arachidonic acid, and collagen, were applied to evaluate the in vitro antiplatelet activities of three active components derived from a traditional Chinese medicine. After analyzing this dataset by quantitative composition–activity relationship modeling, a weighted‐sum optimization method was adopted to calculate the optimal ratio between three components for antiplatelet effects. Further experiments validated our method and showed that better antiplatelet activity was exerted by the optimized combination than the individual component or other combinations. Our findings suggested that the proposed multiobjective optimization approach is a novel method for multicomponent drug design.