Traditional Herbal Medicines, Bioactive Metabolites, and Plant Products Against COVID-19: Update on Clinical Trials and Mechanism of Actions

Abstract

SARS-CoV-2 is the latest worldwide pandemic declared by the World Health Organization and there is no established anti-COVID-19 drug to combat this notorious situation except some recently approved vaccines. By affecting the global public health sector, this viral infection has created a disastrous situation associated with high morbidity and mortality rates along with remarkable cases of hospitalization because of its tendency to be high infective. These challenges forced researchers and leading pharmaceutical companies to find and develop cures for this novel strain of coronavirus. Besides, plants have a proven history of being notable wellsprings of potential drugs, including antiviral, antibacterial, and anticancer therapies. As a continuation of this approach, plant-based preparations and bioactive metabolites along with a notable number of traditional medicines, bioactive phytochemicals, traditional Chinese medicines, nutraceuticals, Ayurvedic preparations, and other plant-based products are being explored as possible therapeutics against COVID-19. Moreover, the unavailability of effective medicines against COVID-19 has driven researchers and members of the pharmaceutical, herbal, and related industries to conduct extensive investigations of plant-based products, especially those that have already shown antiviral properties. Even the recent invention of several vaccines has not eliminated doubts about safety and efficacy. As a consequence, many limited, unregulated clinical trials involving conventional mono- and poly-herbal therapies are being conducted in various areas of the world. Of the many clinical trials to establish such agents as credentialed sources of anti-COVID-19 medications, only a few have reached the landmark of completion. In this review, we have highlighted and focused on plant-based anti-COVID-19 clinical trials found in several scientific and authenticated databases. The aim is to allow researchers and innovators to identify promising and prospective anti-COVID-19 agents in clinical trials (either completed or recruiting) to establish them as novel therapies to address this unwanted pandemic.

Synergic Role of Dexamethasone And Lianhua Qingwen Capsule Accelerate Nucleic Acid Negative Conversion In Severe COVID-19 Patients

“…The ingredients of LHQW recipes, including quercetin, kaempferol, and luteolin, can target ACE2 and 3CLpro to affect viral replication and maturation [21]. At the same time, LHQW reduced systemic and airway in ammation by regulation of the inherent and acquired immune systems through the decrease of IL-6 levels to relieve COVID-19 symptoms [21]. However, in the present study, we failed to show that LHQW alone accelerated nucleic acid negative conversion time.…”

“…3CLpro is a main viral proteinase, which controls the activities of the coronavirus replication complex [20]. The ingredients of LHQW recipes, including quercetin, kaempferol, and luteolin, can target ACE2 and 3CLpro to affect viral replication and maturation [21]. At the same time, LHQW reduced systemic and airway in ammation by regulation of the inherent and acquired immune systems through the decrease of IL-6 levels to relieve COVID-19 symptoms [21].…”

Phytochemicals: Potential Lead Compounds for COVID-19 Therapeutics

“…In spite of the fact that numerous drugs do exist that have clinically proven antiviral properties (Indari et al, 2021) and several drugs that show a limited potential to alleviate COVID-19 symptoms (Lam et al, 2020;Raju et al, 2021), none of them have proven to work efficiently to reduce COVID-19 associated mortality. Nevertheless, several in vitro studies have demonstrated the potential of several phytochemicals to inhibit COVID-19 infectious cycle in humans at various stages (Alam et al, 2021;Behl et al, 2021;Marmitt et al, 2021;Merarchi et al, 2021). These phytochemicals have been demonstrated to inhibit viral entry, viral replication, or viral release -in addition to attenuating the host pathological responses (Figure 2).…”

Targeting autophagy with natural products to prevent SARS-CoV-2 infection

“…Natural products provide a source of bioactive molecules that can be exploited for novel and effective treatments to prevent the fatal evolution of this disease. 2 , 3 , 4 , 5 , 6 These natural biomolecules could interfere at any stage of the virus life cycle, from entering the cell to its replication, assembly, and exit from the cell, as well as by triggering virus clearance. 3 , 7 , 8 , 9 , 10 Autophagy, a vesicular-driven degradation pathway of cellular components, is triggered as a cellular stress response to viral infection, and it is involved in all steps of CoV replication and propagation.…”