Dietary phytochemicals against COVID‐19: A focus on thymoquinone

[...]new mutant variants of coronaviruses are emerging, which could cause the loss of the efficacy of the approved vaccines, mAbs, and small molecule antiviral drugs, exposing the elderly and those with chronic conditions, such as diabetes and cancers. [...]novel vaccines, effective therapies, and affordable management, such as phytochemicals, are highly desirable. Numerous phytochemicals such as flavonoids including quercetin (e.g., apples, onions, parsley, and sage), kaempferol (spinach and kale), isoliquiritigenin (soybean and shallots), tangeretin (tangerine), and baicalein (Scutellaria baicalensis, Huang-qin) (Song et al., 2021) (Figure 1) are shown to be inhibitors of SARS-CoV-2 Mpro with a similar mechanism as Nirmatrelvir in Paxlovid (Mandal et al., 2021). In silico Docking studies suggested TQ can bind human angiotensin-converting enzyme 2 (ACE2) as the receptor of SARS-CoV-2 spike proteins (Jakhmola Mani et al., 2022; Srivastava et al., 2021; Xu et al., 2021) and a sheddase ADAM7 (a membrane-bound metalloprotease) associated with the modulation of ACE2 (He et al., 2022), thus blocking the virus entry to human cells. Clinical trials A phase I clinical trial study showed that TQ-rich black cumin oil (containing 5% of TQ) was safe at 200 mg/adult/day (Thomas et al., 2022).