RESUMO
Cyclotides are mini-proteins with potent bioactivities and outstanding potential for agricultural and pharmaceutical applications. More than 450 different plant cyclotides have been isolated from six angiosperm families. In Brazil, studies involving this class of natural products are still scarce, despite its rich floristic diversity. Herein were investigated the cyclotides from Anchietea pyrifolia roots, a South American medicinal plant from the family Violaceae. Fourteen putative cyclotides were annotated by LC-MS. Among these, three new bracelet cyclotides, anpy A-C, and the known cycloviolacins O4 (cyO4) and O17 (cyO17) were sequenced through a combination of chemical and enzymatic reactions followed by MALDI-MS/MS analysis. Their cytotoxic activity was evaluated by a cytotoxicity assay against three human cancer cell lines (colorectal carcinoma cells: HCT 116 and HCT 116 TP53-/- and breast adenocarcinoma, MCF 7). For all assays, the IC50 values of isolated compounds ranged between 0.8 and 7.3 µM. CyO17 was the most potent cyclotide for the colorectal cancer cell lines (IC50, 0.8 and 1.2 µM). Furthermore, the hemolytic activity of anpy A and B, cyO4, and cyO17 was assessed, and the cycloviolacins were the least hemolytic (HD50 > 156 µM). This work sheds light on the cytotoxic effects of the anpy cyclotides against cancer cells. Moreover, this study expands the number of cyclotides obtained to date from Brazilian plant biodiversity and adds one more genus containing these molecules to the list of the Violaceae family.
Assuntos
Produtos Biológicos , Ciclotídeos , Proteínas de Plantas , Violaceae , Produtos Biológicos/química , Produtos Biológicos/isolamento & purificação , Produtos Biológicos/farmacologia , Brasil , Linhagem Celular Tumoral , Ciclotídeos/química , Ciclotídeos/isolamento & purificação , Ciclotídeos/farmacologia , Humanos , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/farmacologia , Espectrometria de Massas em Tandem , Violaceae/químicaRESUMO
Cyclotides are cyclic peptides, present in several plant families, that show diverse biological properties. Structurally, cyclotides share a distinctive head-to-tail circular knotted topology of three disulfide bonds. This framework provides cyclotides with extraordinary resistance to thermal and chemical denaturation. There is increasing interest in the therapeutic potential of cyclotides, which combine several promising pharmaceutical properties, including binding affinity, target selectivity, and low toxicity towards healthy mammalian cells. Recently, cyclotides have been reported to be orally bioavailable and have proved to be amenable to modifications. Here, we provide an overview of the structure, properties, and pharmaceutical applications of cyclotides.
Assuntos
Ciclotídeos , Descoberta de Drogas/métodos , Sequência de Aminoácidos , Simulação por Computador , Ciclotídeos/síntese química , Ciclotídeos/isolamento & purificação , Ciclotídeos/farmacologia , Bases de Dados Factuais , Humanos , Plantas/químicaRESUMO
Two new bracelet cyclotides from roots of Pombalia calceolaria with potential anticancer activity have been characterized in this work. The cyclotides Poca A and B (1 and 2) and the previously known CyO4 (3) were de novo sequenced by MALDI-TOF/TOF mass spectrometry (MS). The MS2 spectra were examined and the amino acid sequences were determined. The purified peptides were tested for their cytotoxicity and effects on cell migration of MDA-MB-231, a triple-negative breast cancer cell line. The isolated cyclotides reduced the number of cancer cells by more than 80% at 20 µM, and the concentration-related cytotoxic responses were observed with IC50 values of 1.8, 2.7, and 9.8 µM for Poca A (1), Poca B (2), and CyO4 (3), respectively. Additionally, the inhibition of cell migration (wound-healing assay) exhibited that CyO4 (3) presents an interesting activity profile, in being able to inhibit cell migration (50%) at a subtoxic concentration (2 µM). The distribution of these cyclotides in the roots was analyzed by MALDI imaging, demonstrating that all three compounds are present in the phloem and cortical parenchyma regions.
Assuntos
Neoplasias da Mama/tratamento farmacológico , Calceolariaceae/química , Movimento Celular/efeitos dos fármacos , Ciclotídeos/química , Ciclotídeos/farmacologia , Sequência de Aminoácidos , Linhagem Celular Tumoral , Citotoxinas/química , Citotoxinas/farmacologia , Feminino , Humanos , Raízes de Plantas/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodosRESUMO
Plants from the genus Psychotria include species bearing cyclotides and/or alkaloids. The elucidation of factors affecting the metabolism of these molecules as well as their activities may help to understand their ecological function. In the present study, high concentrations of antioxidant indole alkaloids were found to co-occur with cyclotides in Psychotria leiocarpa and P. brachyceras. The concentrations of the major cyclotides and alkaloids in P. leiocarpa and P. brachyceras were monitored following herbivore- and pathogen-associated challenges, revealing a constitutive, phytoanticipin-like accumulation pattern. Psyleio A, the most abundant cyclotide found in the leaves of P. leiocarpa, and also found in P. brachyceras leaves, exhibited insecticidal activity against Helicoverpa armigera larvae. Addition of ethanol in the vehicle for peptide solubilization in larval feeding trials proved deleterious to insecticidal activity and resulted in increased rates of larval survival in treatments containing indole alkaloids. This suggests that plant alkaloids ingested by larvae might contribute to herbivore oxidative stress detoxification, corroborating, in a heterologous system with artificial oxidative stress stimulation, the antioxidant efficiency of Psychotria alkaloids previously observed in planta. Overall, the present study reports data for eight novel cyclotides, the identification of P. leiocarpa as a cyclotide-bearing species, and the absence of these peptides in P. umbellata.
Assuntos
Ciclotídeos/isolamento & purificação , Alcaloides Indólicos/isolamento & purificação , Inseticidas/isolamento & purificação , Inseticidas/farmacologia , Psychotria/química , Sequência de Aminoácidos , Animais , Antioxidantes/química , Brasil , Ciclotídeos/análise , Ciclotídeos/química , Ciclotídeos/farmacologia , Herbivoria , Alcaloides Indólicos/análise , Alcaloides Indólicos/química , Alcaloides Indólicos/farmacologia , Inseticidas/química , Larva/efeitos dos fármacos , Lepidópteros/efeitos dos fármacos , Dados de Sequência Molecular , Estrutura Molecular , Estresse Oxidativo , Folhas de Planta/químicaRESUMO
Plant cyclotides are unusual peptides with low molecular masses and a three-dimensional structure characterized by the presence of a cyclic fold. Synthetic peptides can adopt this circular conformation, but it is not a common feature for most members of other peptide groups. Cyclotides present a wide range of functions, such as the ability to induce stronger contractions during childbirth and anti-tumor activity. Additionally, some cyclotides present anti-viral, insecticidal or proteinase inhibitory activity. In this paper, we describe the structural and functional characteristics of plant cyclotides, their most conserved features and the development of these peptides for human health and biotechnological applications.