Dioclea violacea lectin inhibits tumorigenesis and tumor angiogenesis in vivo.

Dioclea violacea seed mannose-binding lectin (DvL) has attracted considerable attention because of its interesting biological activities, including antitumor, antioxidant, and anti-inflammatory activities. This study evaluated the cytotoxic effect of DvL on tumor and normal cells using the mitochondrial activity reduction (MTT) assay, the carcinogenic and anti-carcinogenic activity by the epithelial tumor test (ETT) in Drosophila melanogaster, and the anti-angiogenic effect by the chick embryo chorioallantoic membrane (CAM) assay. Data demonstrated that DvL promoted strong selective cytotoxicity against tumor cell lines, especially A549 and S180 cells, whereas normal cell lines were weakly affected. Furthermore, DvL did not promote carcinogenesis in D. melanogaster at any concentration tested, but modulated DXR-induced carcinogenesis at the highest concentrations tested. In the CAM and immunohistochemical assays, DvL inhibited sarcoma 180-induced angiogenesis and promoted the reduction of VEGF and TGF-ß levels at all concentrations tested. Therefore, our results demonstrated that DvL is a potent anticancer, anti-angiogenic, and selective cytotoxic agent for tumor cells, suggesting its potential application as a prototype molecule for the development of new drugs with chemoprotective and/or antitumor effects.

Mannose-Binding Lectins as Potent Antivirals against SARS-CoV-2.

The SARS-CoV-2 entry into host cells is mainly mediated by the interactions between the viral spike protein (S) and the ACE-2 cell receptor, which are highly glycosylated. Therefore, carbohydrate binding agents may represent potential candidates to abrogate virus infection. Here, we evaluated the in vitro anti-SARS-CoV-2 activity of two mannose-binding lectins isolated from the Brazilian plants Canavalia brasiliensis and Dioclea violacea (ConBR and DVL). These lectins inhibited SARS-CoV-2 Wuhan-Hu-1 strain and variants Gamma and Omicron infections, with selectivity indexes (SI) of 7, 1.7, and 6.5, respectively for ConBR; and 25, 16.8, and 22.3, for DVL. ConBR and DVL inhibited over 95% of the early stages of the viral infection, with strong virucidal effect, and also protected cells from infection and presented post-entry inhibition. The presence of mannose resulted in the complete lack of anti-SARS-CoV-2 activity by ConBR and DVL, recovering virus titers. ATR-FTIR, molecular docking, and dynamic simulation between SARS-CoV-2 S and either lectins indicated molecular interactions with predicted binding energies of -85.4 and -72.0 Kcal/Mol, respectively. Our findings show that ConBR and DVL lectins possess strong activities against SARS-CoV-2, potentially by interacting with glycans and blocking virus entry into cells, representing potential candidates for the development of novel antiviral drugs.