Design and synthesis of novel quercetin metal complexes as IL-6 inhibitors for anti-inflammatory effect in SARS-CoV-2

Abstract

One of the most common causes of mortality in COVID-19 patients is cytokine release syndrome (CRS). Though several cytokines are involved in CRS, the role of Interleukin 6 is significant. Considering the importance of IL-6 inhibition and the drawbacks of the existing monoclonal antibodies, the present study develops new flavonoid metal complexes as immune boosters targeting IL-6 for SARS-CoV-2 treatment. To identify the potential flavonoids from 152 secondary plant metabolites, PyRx 0.9 tool has been used. The top scorer quercetin was converted into quercetin-oxime. Seven metal complexes (QM-1 to QM-7) were made from quercetin-oxime by utilizing divalent metals such as zinc, copper, magnesium, cobalt, barium, and cadmium. It was assumed that all compounds were moderately soluble and would not penetrate the BBB through in silico ADME studies. However, the in vitro heamolytic research revealed a modest heamolytic effect in all seven complexes. To know the IL-6 inhibitory potential preliminary level, the complexes were screened for cytotoxicity in cell lines MCF-7 which predominantly expresses the IL-6 level. The cytotoxic effects of all complexes were considerable relative to the marketable Nutridac formulation. The complexes quercetin-Zinc (QM1) and quercetin-Zinc-Ascorbic acid (QM7) showed significant cytotoxicity on MCF-7 compared to Nutridac and no cytotoxic toward the normal cell lines.