Bioactive compounds, and bio-activities common to three natural products expected to boost the treatment of the comorbidities of COVID-19: A review

COVID-19, with many variants of its causative virus, has been and is still causing ravages and claiming many lives all over the globe. Currently, there are no therapeutic agents against the disease except for a few already existing ones that are used to manage the symptoms and comorbidities associated with the disease. Even some currently developed vaccines cannot efficiently handle various variants of the causative agent for COVID-19. This review is aimed at utilizing the possible synergy that might exist in the combination therapy of Nigella sativa, Curcuma longa, and honey for better management of COVID-19 and the associated comorbidities. The literature search was performed by inputting some relevant keywords into important search engines and websites such as Google, Google Advanced Search, PubMed, and so on. In vitro studies on some bioactive compounds isolated from N. sativa and C. longa have demonstrated activity against SARS-CoV-2. The three natural products, N. sativa, C. longa, and honey have exhibited wonderful activities against some of the health conditions associated with COVID-19; such include; antiviral, immunomodulatory, antioxidant, anti-inflammatory, bronchodilatory, antihistamine, antitussive, antimicrobial and other activities. Some of the major active compounds responsible for the bioactivities of these products and their mechanisms of action have been highlighted. The products individually have exhibited strong biological activities against conditions associated with COVID-19 and so are expected to exert a synergistic effect when combined in the treatment of the disease even with many variants of the causative organism.