Coronaviruses (CoVs) are a broad group of spherical and enveloped viruses that cause diseases in humans and animals. CoVs have become a major threat to public health in the past two decades, exemplified by epidemics of acute respiratory syndromes and, most recently, the coronavirus disease 2019 pandemic. The envelope of CoVs contains spike (S) proteins, which are transmembrane proteins with a crown-like shape involved in cell attachment, cell‒cell fusion, host tropism, and pathogenesis. The receptors for spike proteins in host cells can be glycans and proteins. This review approaches the structural and functional aspects of the S protein of CoVs. Several issues are presented, including the structure‒function relationship, examples of host receptors, S protein-host cell connection, and its role in the entry of the virus into host cells. The S protein is one of the main targets of studies on the evolutionary relationships between CoVs, mapping of cross-host transmission events, changes in virulence, variations in disease severity level, and the development of therapeutic strategies and vaccines.
Antitumor research leads to the development of new molecules that act specifically in tumor cells by blocking or inhibiting their molecular targets. New therapeutic approaches for the screening of bioactive compounds present in medicinal plants have received increasing attention due to their chemopreventive and chemotherapeutic properties. In ethnomedicine, plants of the genus Vernonia (Asteraceae) are widely used and some have shown several and interesting biological activities, including anticancer. This present study aimed to document experimental evidence supporting the claimed ethnomedical uses of Vernonia species for the treatment of various types of cancer and also to confirm the anticancer potential of these plants. The compounds isolated from aqueous and alcoholic extracts, as well as fractions from different parts of Vernonia plants have acted as potential anticancer agents that inhibited the proliferation of various types of human cancer cell lines, including cervical cancer cells, melanoma cells, promyelocytic leucemia cells, breast adenocarcinoma cells, ovarian cancer, liver cancer cell, and human lung cancer cells. Studies have correlated the antitumor activity of Vernonia plants by inducing apoptosis and modulating mitochondrial signaling pathways controlled by NF-κB, Bcl-2 and p53, as well as inducing DNA damage and arresting the cell cycle at the S-phase checkpoint by oxidative stress. In conclusion, Vernonia species act as a promising source for drug development. However, further studies are needed to explore the exact mechanism of action, pharmacokinetics, chronic toxicological studies, safe dose consumption, and possible interactions with other herbs.
Introdução: Lectinas são glicoproteínas que reconhecem glicoconjugados de superfícies celulares, possibilitando diversas aplicações biotecnológicas. Objetivo: Investigar a presença de lectinas em folhas de A. occidentale e S. cumini Material e métodos: A farinha das folhas secas de S. cumini e A.occidentale foram homogeneizadas em NaCl 0,15 M. Após filtração e centrifugação, o sobrenadante correspondeu ao extrato. As proteínas presentes no extrato foram precipitadas com (NH4)2SO4 obtendo-se a fração proteica F0-60% (após centrifugação/dialise). As preparações foram avaliadas quanto à concentração proteica e a presença de lectinas foi avaliada pela atividade hemaglutinante (AH) utilizando eritrócitos humanos e de coelho. Realizou-se o ensaio de inibição da AH com carboidratos. Para o ensaio do efeito do pH sobre a AH, as F0-60% foram incubadas em tampões na faixa de pH 4-8; Para determinar a estabilidade térmica, as F0-60% foram incubadas entre 30 e 100 °C antes da realização da AH. Resultados: A concentração proteica para S.cumini foi de 5,0 mg/mL(extrato) e 7,0 mg/mL (F0-60%) e de A. occidentale 17 mg/mL (extrato) e 8,6 mg/mL(F0-60%). No ensaio de AH as preparações mostraram maior AH para eritrócitos de coelho. A lectina em F0-60% de S.cumini foi inibida por glicose, galactose, lactose e manose; e A.occidentale por frutose, maltose, manose, e metil-α-D-glicopiranosídeo. Para S.cumini, AHE de F0-60% foi diminuída em toda faixa de pH testada e após aquecimento a 30 ºC. Na F0-60% de A.occidentale, a AHE foi mantida em toda faixa até pH 7,0,diminuíndo em pH 8,0; o aquecimento não alterou a AH. Conclusão: podese deduzir a presença de lectina nas preparações de folhas de A. occidentale e S. cumini, como demonstrado pelos ensaios de AH e de inibição. A Caracterização estrutural e investigação de atividades biológicas estão em planejamento.
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