Synthesis and in vitro cytotoxic activity of a natural peptide of plant origin

Synthesis, Anticancer, and Antimicrobial Evaluation of Integerrimide-A

Integerrimide-A (IG-A) is a cyclic heptapeptide that was recently synthesized after being recovered from the latex of the Jatropha integerrima tree. This was achieved by first coupling a tetrapeptide unit (Boc-Gly-L-Leu-L-Leu-L-Leu-OMe) with a tripeptide unit (L-Thr-L-Pro-L-Trp-OMe). The characterization was done by using spectral techniques like FT-IR, 1H-NMR, mass spectrometry, and elemental analysis of the newly synthesized cyclic molecule. Antimicrobial and anticancer properties of IG-A were tested using a biological screening. Gram +ve bacteria (B. subtilis and S. aureus) and Gram -ve bacteria (P. aeruginosa and E. coli) were used in the antibacterial testing. Fungal strains such as C. albicans, A. niger, T. mentagrophytes, and M. audouinii were used to test the antifungal activities. Antimicrobial activity analysis revealed that cyclic peptide—IG-A (8)—has modest antibacterial activity and antifungal activities, when compared with the standard drugs ciprofloxacin and griseofulvin, respectively. Comparable MTT assays were performed on HCT116 (human colon carcinoma) and B16F10 (melanoma cells) cell lines with doxorubicin as the standard drug to determine the cytotoxic activity of the synthesized cyclic peptide. Inhibition of growth of HCT116 and B16F10 cell lines was used to calculate the cytotoxic effect. At a dosage of 120 μg/mL, the cyclopeptide IG-A (8) inhibited cell proliferation by 87.5 and 72.5 percent, respectively. Cyclopeptide IG-A had CTC50 values of 77.65 μM and 68.63 μM against HCT116 and B16F10, respectively. The % growth inhibitions at lesser levels are 72.5 and 50 at 60 μg/mL, respectively. The standard drug inhibited growth by 100 percent with CTC50 values of 48.63 μM and 43.25 μM against HCT116 and B16F10, respectively. From the results, it is concluded that IG-A has considerable antimicrobial and cytotoxic effects. Internucleosomal DNA fragmentation may be the underlying mechanism in HCT116 cells, whereas the suppression of eumelanin synthesis in B16F10 cells is another possibility.

Toward the Synthesis of a Heterocyclic Analogue of Natural Cyclooligopeptide with Improved Bio-Properties

AIMS

The present investigation is targeted toward the synthesis of a novel analogue of a natural peptide of marine origin. <P> Background: Marine sponges are enriched with bioactive secondary metabolites especially circular peptides. Heterocycles are established organic compounds with potential biological value. Taking into consideration the bio-properties of heterocycles and marine sponge-derived natural peptides, an effort was made for the synthesis of a heterocyclic analogue of a natural cyclopeptide. <P> Objective: A heterocyclic analogue of a sponge-derived proline-containing cyclic peptide, rolloamide A, was synthesized by interaction of Boc-protected L-histidinyl-L-prolyl-L-valine and L-prolyl-L-leucyl-L-prolyl-L-isoleucine methyl ester and compared with synthetic rolloamide A with bioactivity against bacteria, fungi, and earthworms. <P> Methods: The synthesis of cycloheptapeptide was accomplished employing the liquid phase method. The larger peptide segment was prepared by interaction of Boc-protected L-prolyl-L-leucine with L-prolyl-L-isoleucine methyl ester. Similarly, the tripeptide unit was synthesized from Boc-protected L-histidinyl-L-proline with L-valine ester. The linear heptapeptide segment (7) was cyclized by utilizing pentafluorophenyl (pfp) ester, and the structure was elucidated by elemental and spectral (IR, 1H/13C NMR, MS) analysis. The peptide was also screened for diverse bioactivities such as antibacterial, antifungal, and potential against earthworms and cytotoxicity. <P> Results: The novel cyclooligopeptide was synthesized with 84% yield by making use of carbodiimides. The synthesized cyclopeptide exhibited significant cytotoxicity against two cell lines. In addition, promising antifungal and antihelmintic properties were observed for newly synthesized heterocyclic peptide derivative (8) against dermatophytes and three earthworm species at 6 µg/mL and 2 mg/mL, respectively. <P> Conclusion: Solution-phase technique employing carbodiimide chemistry established to be promising for synthesizing the cycloheptapeptide derivative (8), and C5H5N was proved a better base for heptapeptide circling, when compared to N-methylmorpholine and triethylamine.

Natural cyclic polypeptides as vital phytochemical constituents from seeds of selected medicinal plants

Cyclopolypeptides are among the most predominant biomolecules in nature, especially those derived from plant seeds. This category of compounds has gained extraordinary attention due to remarkable variety of structures and valuable biofunctions. These congeners display enormous variation in terms of both structure and function and are the most significant biomolecules due to their widespread bioproperties. The estrogenic activity, immunosuppressive activity, cytotoxicity, vasorelaxant activity, and other properties possessed by cyclic peptides from seeds of plants make these congeners attractive leads for the drug discovery process. The current study covers the important structural features, structure-activity relationship, synthesis methods, and bioproperties of plant seeds-originated bioactive peptides from Vaccaria segetalis, Linum usitatissimum, and Goniothalamus leiocarpus, which may prove vital for the development of novel therapeutics based on a peptide skeleton.

Natural Bioactive Thiazole-Based Peptides from Marine Resources: Structural and Pharmacological Aspects

Peptides are distinctive biomacromolecules that demonstrate potential cytotoxicity and diversified bioactivities against a variety of microorganisms including bacteria, mycobacteria, and fungi via their unique mechanisms of action. Among broad-ranging pharmacologically active peptides, natural marine-originated thiazole-based oligopeptides possess peculiar structural features along with a wide spectrum of exceptional and potent bioproperties. Because of their complex nature and size divergence, thiazole-based peptides (TBPs) bestow a pivotal chemical platform in drug discovery processes to generate competent scaffolds for regulating allosteric binding sites and peptide–peptide interactions. The present study dissertates on the natural reservoirs and exclusive structural components of marine-originated TBPs, with a special focus on their most pertinent pharmacological profiles, which may impart vital resources for the development of novel peptide-based therapeutic agents.

Total Synthesis and Pharmacological Investigation of Cordyheptapeptide A

The present investigation reports the synthesis of a phenylalanine-rich N-methylated cyclopeptide, cordyheptapeptide A (8), previously isolated from the insect pathogenic fungus Cordyceps sp. BCC 1788, accomplished through the coupling of N-methylated tetrapeptide and tripeptide fragments followed by cyclization of the linear heptapeptide unit. Structure elucidation of the newly synthesized cyclopolypeptide was performed by means of FT-IR, ¹H-NMR, 13C-NMR, and fast atom bombardment mass spectrometry (FABMS), and screened for its antibacterial, antidermatophytic, and cytotoxic potential. According to the antimicrobial activity results, the newly synthesized N-Methylated cyclopeptide exhibited potent antibacterial activity against Gram-negative bacteria Pseudomonas aeruginosa and Klebsiella pneumoniae and antifungal activity against dermatophytes Trichophyton mentagrophytes and Microsporum audouinii at a concentration of 6 μg/mL, in comparison to the reference drugs, gatifloxacin and griseofulvin. In addition, cyclopolypeptide 8 displayed suitable levels of cytotoxicity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines.

First Total Synthesis and Biological Screening of a Proline-Rich Cyclopeptide from a Caribbean Marine Sponge

A natural heptacyclopeptide, stylissamide G (7), previously isolated from the Bahamian marine sponge Stylissa caribica from the Caribbean Sea, was synthesized via coupling of the tetrapeptide l-phenylalanyl-l-prolyl-l-phenylalanyl-l-proline methyl ester with the tripeptide Boc-l-leucyl-l-isoleucyl-l-proline, followed by cyclization of the linear heptapeptide fragment. The structure of the synthesized cyclooligopeptide was confirmed using quantitative elemental analysis, FT-IR, ¹H NMR, ¹³C NMR and mass spectrometry. Results of pharmacological activity studies indicated that the newly synthesized cycloheptapeptide displayed good anthelmintic potential against Megascoplex konkanensis, Pontoscotex corethruses and Eudrilus eugeniea at 2 mg/mL and in addition, potent antifungal activity against pathogenic Candida albicans and dermatophytes Trichophyton mentagrophytes and Microsporum audouinii at a concentration of 6 μg/mL.

Medicinal property, phytochemistry and pharmacology of several Jatropha species (Euphorbiaceae): a review

The genus Jatropha (Euphorbiaceae) comprises of about 170 species of woody trees, shrubs, subshrubs or herbs in the seasonally dry tropics of the Old and the New World. They are used in medicinal folklore to cure various diseases of 80% of the human population in Africa, Asia and Latin America. Species from this genus have been popular to cure stomachache, toothache, swelling, inflammation, leprosy, dysentery, dyscrasia, vertigo, anemia, diabetis, as well as to treat HIV and tumor, opthalmia, ringworm, ulcers, malaria, skin diseases, bronchitis, asthma and as an aphrodisiac. They are also employed as ornamental plants and energy crops. Cyclic peptides alkaloids, diterpenes and miscellaneous compounds have been reported from this genus. Extracts and pure compounds of plants from this genus are reported for cytotoxicity, tumor-promoting, antimicrobial, antiprotozoal, anticoagulant, immunomodulating, anti-inflammatory, antioxidant, protoscolicidal, insecticidal, molluscicidal, inhibition AChE and toxicity activities.

Total synthesis and antimicrobial activity of a natural cycloheptapeptide of marine origin

The present study deals with the first total synthesis of the proline-rich cyclopolypeptide stylisin 2 via a solution phase technique by coupling of the Boc-L-Pro-L-Ile-L-Pro-OH tripeptide unit with the L-Phe-L-Pro-L-Pro-L-Tyr-OMe tetrapeptide unit, followed by cyclization of the resulting linear heptapeptide fragment. The chemical structure of the finally synthesized peptide was elucidated by FTIR, ¹H/¹³C-NMR and FAB MS spectral data, as well as elemental analyses. The newly synthesized peptide was subjected to antimicrobial screening against eight pathogenic microbes and found to exhibit potent antimicrobial activity against Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans, in addition to moderate antidermatophyte activity against pathogenic Trichophyton mentagrophytes and Microsporum audouinii when compared to standard drugs--gatifloxacin and griseofulvin.