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The Role of Natural Products in COVID-19
Published in Hanadi Talal Ahmedah, Muhammad Riaz, Sagheer Ahmed, Marius Alexandru Moga, The Covid-19 Pandemic, 2023
Iqra Akhtar, Sumera Javad, Tehreema Iftikhar, Amina Tariq, Hammad Majeed, Asma Ahmad, Muhammad Arfan, M. Zia-Ul-Haq
Quercetin is a common flavonoid that is found in a number of medicinal plants. Lemon (C. limon) is also rich in quercetin. It has shown strong anti-influenza virus activity previously [84]. Quercetin is known to impair the expression of influenza virus protein [85]. It was particularly found very active against initial stages of viral attack. It has also been in common use since a long for treating common cold [86]. Quercetin also showed predominant detrimental effects on hepatitis C virus (HCV) by hindering the replication of virus inside the host cells quercetin can control the viral load directly itself or by host mediated interference to the viral life cycle [87]. It can suppress the activities of various viral enzymes like proteases, reverse transcriptases, DNA gyrases and polymerases [88–91]. The half-life of quercetin in human body is 25 hours, so its higher levels in blood plasma can be easily maintained for longer to treat viral infections without multiple doses [92].
The Integrative Coronary Heart Disease (CHD) Prevention Program
Published in Mark C Houston, The Truth About Heart Disease, 2023
Quercetin, a flavonoid found in fruits and vegetables, has unique biological properties that may improve CHD and other cardiovascular problems. It also has other properties including anticarcinogenic, anti-inflammatory (lowers HS-CRP), antiviral, antioxidant, and has the ability to inhibit lipid peroxidation, platelet aggregation, and capillary permeability, and stimulate mitochondrial biogenesis. Quercetin (25 mg/kg) administered to rabbits on a high cholesterol diet had reduced progression and increased regression of atherosclerosis. It lowers the oxidative stress substance called myeloperoxidase (MPO), increases the removal of LDL cholesterol from cells called reverse cholesterol transport (RCT), and increases paraoxonase 2 (PON 2), which improves HDL function and decreases the oxidation of LDL. In addition, quercetin will improve endothelial function and increase nitric oxide, lower blood pressure, and decrease platelet aggregation and thrombosis. Exercise endurance is enhanced. There is an increase in muscle mitochondria in humans. Quercetin may slow aging by blocking senescence proteins.
Anti-Proliferative Properties of Various South African Buddleja Species
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
The isolated compounds from this plant include flavonoids (apigenin-7-O-glucoside, quercetin and luteolin) and phenylpropanoids (2-acetylmartynoside and isomartynoside). The presence of inflammation within the body allows the development of cancer and aids in the progression of all stages of tumorigenesis. If the immune response is not restored to homeostasis, it could lead to chronic inflammation, immunosuppression and excessive proliferation. Apigenin-7-O-glucoside is a stable natural flavonoid that has anti-inflammatory activity and exhibits anti-proliferative activity against the colon cancer cell line HCT116 with an IC50 of 15 µM (Smiljkovic et al., 2017). Apoptosis in these cells was induced by the pro-apoptotic proteins Bcl-2-association X protein (Bax) and tumor protein p53 (Smiljkovic et al., 2017). Quercetin has anti-inflammatory activity, due to its ability to inhibit the COX-2 protein, and has immune-modulatory activity (Pendota et al., 2014).
Quercetin improves the imbalance of Th1/Th2 cells and Treg/Th17 cells to attenuate allergic rhinitis
Published in Autoimmunity, 2023
Xia Ke, Ziqi Chen, Xiaoqiang Wang, Houyong Kang, Suling Hong
Chinese medicine has been widely concerned in the treatment of diseases due to its effectiveness and safety. Quercetin is a hydroxyl phenolic compound, which is an important representative of the flavonoid subclass. It exists in a variety of plants and regulates plant growth and development [10]. Moreover, quercetin has many biological activities, such as antioxidant, antiviral, anti-inflammatory, and anti-allergic effects [11,12]. Accumulating evidence has shown that quercetin is used to treat and prevent diseases, including cancers, cardiac diseases, inflammation, and metabolic diseases [13]. Quercetin plays a central role in a variety of allergic diseases, including AR. It regulates the Th1/Th2 balance and reduces the release of IgE antibodies [12,14]. However, the regulation of quercetin in the Treg/Th17 balance remains largely unknown.
Neuroprotective effects of quercetin on the cerebellum of zinc oxide nanoparticles (ZnoNps)-exposed rats
Published in Tissue Barriers, 2023
Shaimaa A. Abdelrahman, Amal S. El-Shal, Abeer A. Abdelrahman, Ebtehal Zaid Hassen Saleh, Abeer A. Mahmoud
Much prior research suggested that Quercetin may possess antioxidant and anti-inflammatory properties due to its free radical scavenging and metal-chelating capacities.48–50 The anti-inflammatory/anti-allergic property of Quercetin was attributed to mast cell membranes stabilization so, preventing the release of histamine and other inflammatory mediators in the body. It was shown to reduce IL-6 and TNFα in lipopolysaccharide in murine macrophages.51 Quercetin also prevents glial cells from releasing proinflammatory cytokines. It protects against neuroinflammation by decreasing the formation of nitric oxide (NO) in microglial cells, which inhibits NF-B signaling.52–55 Similarly, Quercetin has been shown to reduce manganese neurotoxicity via reducing neuroinflammation-mediated neurodegeneration, by regulating the heme oxygenase-1 (HO-1)/nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear NF-B pathways.56
Folic acid: a potential inhibitor against SARS-CoV-2 nucleocapsid protein
Published in Pharmaceutical Biology, 2022
Yu-meng Chen, Jin-lai Wei, Rui-si Qin, Jin-ping Hou, Guang-chao Zang, Guang-yuan Zhang, Ting-ting Chen
In the association analysis of TCM and CWM, three central compounds were identified; baicalein, oestrone, and quercetin. Baicalein is a flavonoid with antihyperglycemic activity (Dinda et al. 2017). Quercetin is also a flavonoid; it exhibits beneficial effects on inflammation and immunity (Li et al. 2016). Studies have shown that quercetin may decrease the frequency and duration of respiratory tract infections as an effective intervention; however, further research is needed (Aucoin et al. 2020). Natural oestrogens mainly comprise oestradiol, oestrone, and oestriol. It has been shown that oestrogen treatment silences inflammatory reactions and decreases virus titres, leading to improved survival rates in animal experiments (Zsuzsanna 2020). GO analysis was performed on the overlapping fraction of targets obtained from target association analysis of TCM and CWM to obtain target enrichment in the cytosol and protein binding category. KEGG analysis was performed to obtain target enrichment in the pathways of cancer and hepatitis B. The commonality between TCM and CWM for the treatment of COVID-19 has been shown.