Every part of bitter kola (Garcinia kola Heckel) is traditionally used in Africa to treat typhoid fever, bronchitis, bacterial infections, malignant tumors, skin infections, tuberculosis, gastritis, colds, and jaundice [85,86]. The plant is indigenous to Africa and pharmacologically evaluated in animal studies to have antiviral, antiasthma, antioxidant, antidiabetic, antihypertensive, antibacterial, antiasthma, and hepatoprotective activities [87,88,89]. Although G. kola has not been scientifically documented for use in pandemics, its traditional usage and bioactive constituents make the plant a candidate for use in pandemics and epidemics in Africa [85]. For instance, in recent reviews, G. kola has been suggested as a potential and promising medicinal plant for the treatment of coronaviruses due to its antiviral and antioxidant activities [90,91,92]. Similarly, G. kola, the active constituent of G. kola, has been reported to be active against polioviruses, measles virus, yellow fever virus, influenza, and herpes simplex virus-1 [93,94]. G. kola’s immunorestorative and immunomodulatory activities make it a significant plant in diseases causing immunodeficiencies, such as COVID-19 and AIDS [95]. The bioactive compounds found in G. kola include alkaloids, phenols, saponins, sterols, tannins, garciniflavanone, kolanone, garcinoic acid, kolaflavanone, and kolaviron [85,89,96]. The seed is also rich in phosphorous and potassium [96]. Kolavoviron has significant anti-inflammatory and antioxidant activity. It was reported to be effective against viruses via immunomodulating activities, metal chelating, and as a potent radical scavenger [93,97,98]. Furthermore, kolavoviron modulate oxidative stress via stimulation of phase 2 detoxification of enzymes, proving its chemopreventive effects. This action mitigates the expression of COX-2 and iNOS at the molecular level, downregulating AP-1 DNA and NF-kB binding, and mitigating oxidative damage to biomolecules [97,99,100]. Other derivatives of G. kola, such as guttiferones and garcinol, have been reported to inhibit the cytopathic effects of HIV [101]. Toxicological studies in rats and mice showed G. kola to be safe [102]. The long history of the seed’s usage and the safe toxicological profile make G. kola a suitable candidate for clinical trials in pandemics.

Dihydroxybishopsolicepolide, scopoletin, acacetin, flavonoids, and yomogiartemin are the common phytochemicals identified and described in Artemisia [103,104]. The shrub is abundant in Northern, Eastern, and Southern Africa. It has been reported for use traditionally in treating influenza, respiratory infections, cough, malaria, diabetes, and fever [105]. The plant’s bioactive ingredients have been reported to have potent antioxidant activity through scavenging hydrogen peroxide and hydroxyl ions and modulating reactive oxygen species, thus, making Artemisia a protective agent that strengthens the antioxidant defense mechanism [106]. Furthermore, the phytochemicals in Artemisia and their derivatives provided selective cytotoxicity in randomized double-blinded subjects treated for colorectal cancer [107]. Slezakova and Ruda-Kucerova (2017) [108] further reported Artemisia’s promising potential in hepatocellular carcinoma, lung cancer, and breast cancer.

Artemisia also has significant antiviral activities against influenza virus A, human herpes viruses 1 and 2, hepatitis B and C, and HIV-1 viruses [109,110,111]. Artemisia’s general mechanism of action blocks the host-cell–type and metabolic requirements for viral replication by inhibiting the central regulatory activity of viral-infected cells [109,111,112].

Artemisia is an African indigenous traditional medicinal plant for treating diseases associated with pandemics and epidemics. Its antioxidant, anti-inflammatory, antiviral activities, low toxicity, and safety make Artemisia a potential drug candidate for the prevention and treatment of diseases in pandemics and epidemics on the continent of Africa [105,113].

One of the most valuable African plant species widely applied in traditional medicine is P. guineense. The plant has potent antioxidant properties with strong antibacterial, anticancer, and antiviral properties [114]. An ethnopharmacological survey showed that the plant is used in traditional African settings for sexually transmitted diseases [115]. Piperine, piperlongumine, ligans, monoterpenes, terpenoids, sterols, sesquiterpenes, and volatile oils are some of the bioactive compounds in P. guineense [116]. These alkaloids are scaffolds for discovering new drugs since they contain antimicrobial pharmacological properties [117,118]. For instance, piperine, a potent antibacterial agent, inhibits the efflux pump in Staphyloccocus aureus, making it a potential phytochemical for multidrug-resistant bacteria [119].

Furthermore, a recent study suggested that a combination of piperine and rifampicin improved rifampicin’s effectiveness, making piperine an agent that can reduce the adverse effects of rifampin when used in clinical therapy [120]. Apart from piper’s reported effectiveness as an anti-inflammatory and antiproliferative, the bioactive compound was also reported to demonstrate protection against chronic diseases based on clinical studies [110]. Furthermore, piperlongumine is effective as an anticancer, antifungal, antihelminth, and in treating many neglected tropical diseases in Africa, making P. guineense a valuable plant used in pandemics [110]. The effectiveness of piperlongumine in neurodegenerative diseases is due to its ability to inhibit or reduce the synthesis of prostaglandins E₂, nitric oxide, cyclooxygenases-2, nuclear factor kappa B, interleukin-6, and tumor necrosis factor-alpha 9 [121,122]. Osho et al. (2016) reported the antiviral activity of P. guineense’s methanolic extract in broiler chickens infected with Newcastle disease virus (NDV) [123]. The numerous underlying mechanisms of action and multitargeting potentials of P. guineense are still being studied, even though the benefits have existed in Africa for a long time [122].

The origin of Achyranthes aspera is in Africa, even though some literature indicates that the plant is also to be native to South Asia [124]. The plant has been associated with its usefulness in pandemics due to its significant antioxidant and immune-boosting abilities and its antiviral effects [124,125]. The antiviral potential of a methanolic extract of Achyranthes aspera was evaluated against herpes simplex virus type 1 and type 2. A. aspera demonstrated good anti-Herpes simplex virus activity [125]. In addition to its usefulness in pandemics, the entire part of A. aspera has been traditionally used in Africa and other parts of Asia for dysentery, arthritis, malaria, hemorrhoids, fever, pain, and diarrhea [124]. In addition, the plant is diuretic, anti-inflammatory, antiasthmatic, and valuable for pneumonia [126,127,128].

Triacontanol, eugenol, ecdysterone, and betaine are the main bioactive compounds in A. aspera. Furthermore, the plant’s antioxidant and immune-boosting activities are enhanced by ascorbic acid [128,129,130,131]. The ascorbic acid in A. aspera significantly boosts immunity and alleviates inflammation in the SARS-coronavirus by conferring antioxidant properties [92]. The chemopreventive effects of A. aspera have also been reported in a few studies. Saponin fractions of A. aspera considerably reduce early antigen activation elicited by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate in Raji cells by Epstein-Barr virus. [132]. Furthermore, A. aspera induced apoptosis through a mitochondrial-mediated pathway [133].

Garlic (Allium sativum L., Fam. Liliaceae), though historically believed to originate from West China, is presently cultivated and used globally as a spice, immune booster, and a remedy during pandemics. Garlic is the first remedy to prevent and treat pandemics, such as influenza, typhus, cholera, and dysentery [134]. Garlic was fed to pyramid builders to boost immunity and was reported as a nutritional supplement in ancient inscriptions in Egyptian pyramid plates. In addition, garlic provided the builders with vitamins, balance, and the energy to pull the heavy plates used in building the pyramids [135].

Traditionally, garlic has been used in Africa to manage bacterial, parasitic, viral, and other infectious diseases [136,137,138]. Other uses included gynecological diseases, toothaches, snake bites, arthritis, and hypertension [136,137,139,140]. In general, garlic extracts are effective as antioxidants, anticancer, and antimicrobials and tend to reduce the risk of cardiovascular events [134,141,142]. Experimental animal and clinical studies have provided evidence of garlic’s effectiveness in managing the common flu, diabetes, hypertension, arthritis, and cancer prevention [142,143].

Over a hundred bioactive compounds are found in garlic, with allicin (thiosulfate) being the most active and responsible for garlic taste and smell [144]. Other sulfur-containing bioactive substances found in garlic include diallyl trisulfate, ajoenes, diallyl disulfide (sulfides), 2-vinyl-(4H)-1,3-dithiin, 3-vinyl-(4H)-1,2-dithiin (vinyldithiins), and alliin, which, constitutes majorly cysteine sulfoxide [145,146,147].

Garlic is used in pandemics due to its antioxidant, antiviral, and antibacterial activities [88]. Reduction in the synthesis of oxygen-free radical species has been reported with garlic when it is frequently consumed, promoting antioxidant activity [147,148]. Similarly, garlic extracts have been reported to reduce glutathione peroxides and superoxide dismutase in rats’ hepatic tissues [149,150]. In addition, high radical scavenging activity with different sulfur-containing substances in garlic, phenols, and flavonoids has been demonstrated with garlic extracts [151]. Other antioxidant activities of the bioactive compounds in garlic include a decrease in the synthesis of reactive nitrogen and oxygen species by diallyl sulfide through the enzymatic suppression of cytochrome P450-2E1, leading to hepatoprotection [147,152]; inhibition and H₂O₂-induced DNA damage with saponins extracted from garlic [153]; and the inhibition of NADPH oxidase 1 through the prevention of reactive oxygen species with alliin [154].

In a recent review, Batiha et al. (2020) [147] reported that garlic extract is effective against diverse viruses, such as vesicular stomatitis virus, human rhinovirus type 2, influenza virus type 3, human cytomegalovirus, influenza B type virus, and herpes simplex 1 and 2 [155]. The inhibition of adhesive interaction and fusion of leukocytes with ajoenes; inhibiting the synthesis of thiol enzymes by allicin; and the enhancement of natural killer-cell activity through the destruction of cells infected by viruses’ diallyl trisulfide on human cytomegalovirus are a few mechanisms of garlic’s action [147,155]. Finally, allicin has a wide range of activities against many bacterial organisms, including K. aerogenes, E. faecalis, S. enterica, E. coli, S. pyogenes, S. mutans, Mycobacteria, Shigella, P. vulgaris, and P. aeruginosa [137,149,156,157,158,159]. The ability of garlic to inhibit NF-kB and modulate cytokine expression makes it an immunomodulatory and effective plant for pandemics in Africa. Finally, prostaglandin-E2, COX-2, and nitric oxide production inhibition lead to a significant reduction in the synthesis of inflammatory interferon γ, interleukin-6, and TNF- α with garlic [159].

Moringa oleifera is commonly called the miracle tree in Africa because of its numerous traditional and pharmacological activities against various diseases. The plant’s multipurpose nutritional and health benefits have been widely reported in Africa and most parts of the world [140,160,161,162]. The plant has been traditionally used in Africa for food, livestock feed, nutrition, and medicine [163]. Recently, Moringa has been used in biofuel production, cosmetics, and water purification [161,164]. The phytochemicals responsible for Moringa’s biological effects include isothiocyanate, phenolic acids, polyphenols, sterols, alkaloids, terpenes, flavonoids, and flavanol glycosides [160,161,162,163]. Some ethnopharmacological activities of moringa include antioxidant, parasitic diseases, antituberculosis, anticancer, antidiabetic, anti-inflammatory, sexually transmitted infections, typhoid fever, cardioprotective, neuroprotective, antihypertensive, and hepatoprotective effects [162]. Even though moringa significantly decreased triglyceride, cholesterol, and glucose levels in rats; the plant is safe and has a high therapeutic index [165]. Moringa leaves are rich in beta carotene, minerals, and proteins, essential compounds lacking in most populations found in developing nations. The ability of Moringa to boost the immune system and help the body fight infections has been reported. The plant showed some significant activities against various viruses, including HIV, and has been reported to be used in managing AIDS and diseases related to AIDS infections [166,167]. In addition, Moringa is effective against the influenza A virus, new castle disease virus, herpes simplex virus, Epstein-Barr virus, hepatitis B virus, and foot-and-mouth disease virus in cloven-footed animals [168]. Protection of infected host cells from cytopathic effect; decrease in the levels of cytokines; inhibition of the expression and nuclear transfer of cellular proteins transcription factor EB leading to a weakening of the autophagy infected cells; and the inhibition of viral replication in host cells are some of the reported antiviral mechanisms of action of moringa [169]. These biologic activities made Moringa an African medicinal plant used to prevent and treat pandemics and diseases related to pandemics in the African continent.

Zingiber officinale R. (Fam Zingiberaceae) is presently widely cultivated in most African countries for the prevention and treatment of common influenza, cough, sore throats, arthritis, lung diseases, peptic ulcer disease, hypertension, and infectious diseases, such as bacterial and viral infections. Although Ginger was initially used as a food spice and for medicinal plants in China, the use of ginger in Africa for the prevention and treatment of diseases has been documented [170]. Presently over 100 species of ginger are cultivated worldwide; however, Z. officinale is the most cultivated and used as an ingredient for food and medicinal plants [171,172].

The US Department of Agriculture (2013) identified steroids, phenols, and alkaloids as the bioactive compounds found in ginger with therapeutic activities. Other active compounds include gingerols, zingerone, zingiberol, paradols, and shogaols [173,174,175,176]. Ginger has been widely reported to have antiarthritic, anticancer, antioxidant, anti-rhinoviral, antimicrobial, and antiglycemic pharmacological activities [174,177,178]. Shogaol and gingerol have significant pharmacological activity compared to other bioactive compounds found in ginger [179].

Ginger’s antiviral, antioxidant, and antibacterial effects make it a viable medicinal herb and spice used to prevent and manage pandemics in Africa [180]. Chang et al. (2013) demonstrated that fresh ginger acts by blocking viral attachments and internalization and is effective against human respiratory syncytial virus-induced plaque formation on airway epithelium [181]. Similarly, Rathinavel et al. (2020) reported that 6-gingerol, a phytocompound from Z. officinale, showed high binding affinity against SARS COVID-19, including spike proteins, RNA binding, and viral proteases proving antiviral activity, making 6-gingerol a promising bioactive compound for COVID-19. Good ADME pharmacokinetic properties and excellent drug-likeness parameters with zero rule violations were demonstrated by 6-gingerol [182]. Generally, the Zingiberaceae plant family (Zingiber officinale, Curcuma longa, and Aframomum melegueta) is effective against a wide variety of viruses, such as Enterovirus 71, Japanese encephalitis virus, Epstein-Barr virus, Herpes simplex virus types 1 and 2, influenza A virus, human immunodeficiency viruses, coronavirus SARS-CoV-1, rhinovirus, chikungunya virus, and respiratory syncytial virus. In addition, these herbs are significant immune system boosters and excellent sources of nutrition [180].

Furthermore, besides possessing antiviral activities, Z. officinale has significant antioxidant activities. Zingerone, for instance, suppresses lipid peroxidation and scavenges hydroxyl ions and peroxides [183,184,185]. Similarly, 6-gingerol effectively protects against ultraviolet B-induced skin disorders in rats by inhibiting the induction of NF-kappa translocation, proteins, and cyclooxygenase-2 mRNA [186]. Z. officinale terpenoids significantly rendered endometrial cancer cells ineffective by promoting the stimulation of p53 [178]. In addition, the combination of 10-gingerol, 8-gingerol, 6-gingerol, and 6-shogaol prevented the rapid multiplication of PC-3 prostate cancer cells, thereby providing cytoprotective effects [186,187]. Other studies on ginger’s cytoprotective effects reported ginger powder suppressing the synthesis of the COX-1 enzyme associated with intestinal cancers [188]. Similarly, a decrease in the synthesis of metalloproteinase-9 and the colonization of breast cancer cells was demonstrated by 6-shogaol [189]. In addition, 6-gingerol stimulates the generation and formation of new blood vessels, aiding in the prevention of the spread of cancer cells [190]. Preventing the synthesis of prostaglandin synthase or 5-lipoxygenase with gingerol and shogaol effectively inhibits the expression of prostaglandins and leukotrienes [191,192]. Although the rhizome is commonly used, all the parts of ginger are utilized in African traditional medicine [92].

Bitter melon (Momordica charantia) has been used as a medicinal plant to treat viral and gastrointestinal infections and for ritual purposes in Africa [193]. Bitter melon has been traditionally used to treat diabetes [194]. It contains several bioactive compounds that contribute to its antiviral and antioxidant activities [193,195,196]. The fruit contains minerals, vitamins, phenolic compounds, triterpenes, lipids, proteins, glycosides, steroids, saponins, and flavonoids [195].

M. charantia possessed antiviral activities and was reported to be effective against HIV-1, dengue virus, and hepatitis B [197]. Rebultan (1995) reported that M. charantia significantly increased and normalized CD4 count and CD4/CD8 ratio in HIV-infected persons while reducing recurrent respiratory infections [198].

In addition, M. charantia has been suggested as a promising anticancer agent whose bioactive compounds target cancer cells and are used to correct metabolic aberrations [199]. Autophagy and apoptosis are the mechanisms of action of M. charantia-mediated cell death in colon and breast cancers, respectively [200,201]. The plant’s potential medicinal effects and applications for HIV, diabetes, and cancers made it a good candidate for the treatment of pandemic-related viral diseases and to boost immunity in poor African populations where sophisticated healthcare systems are not available [194,197,200,202]. The variety of steroids and protein compounds isolated from M. charantia, such as kuguacin C and kuguacin E, give the plant its antiviral properties. In a recent review, Jia et al. (2017) summarized the antiviral activity of the Momordica anti-HIV protein of 30 kD (MAP30). The extracted protein from M. charantia inhibits HIV-1 DNA replication in monocytes and selectively kills lymphocytes and macrophage-infected with HIV with minimal toxicity to the cells unaffected by HIV [196]. With a rich collection of phytochemicals and years of successful application in managing and preventing various diseases, M. charantia is a potential source of relief in managing Africa’s present and future epidemics and pandemics.

Several African scientists have reported the use of C. longa in African traditional folk medicine and its use as a food spice [203,204,205,206]. Although the plant is cultivated throughout the entire continent of Africa and other parts of the world, Western and Eastern Africa seem to have wider plant cultivation than the rest of Africa [207]. C. longa has been traditionally reported for use in conjunctivitis, smallpox, and sinusitis [205,206,208]. The plant has antioxidant, anticancer, immunomodulator, and antimicrobial properties [206,208]. These pharmacological potentials and properties of C. longa have been exploited in Africa for pandemics and epidemics [208]. Curcuminoids, quercetin, curcumin, zingiberine, borneol, alpha-phellandrene, and a variety of sesquiterpenes are some of the bioactive phytochemicals found in C. longa [204,206,208]. Aggarwal et al. (2016) reported curcumin as a potent antioxidant by suppressing NF-κB and NF-α, in addition to its antibacterial effect on organisms, such as Vibrio cholera and Klebsiella pneumonia [208]. Furthermore, African C. longa possessed substantial antiviral activities making it a potential plant in pandemics associated with viruses. The plant is effective against HIV-1, H1N1, hepatitis C, parainfluenza virus type 3, H6N1, human papillomavirus, and coxsackievirus B3 [204,206,208]. The ability of curcumin to inhibit viral hemagglutination, suppress viral replication, and down-regulate viral transcription made curcumin a candidate for use in pandemics [208]. The antibacterial, antiviral, anti-inflammatory, and antioxidant activities of C. longa made the plant a valuable and potential therapy in pandemics throughout Africa [209].

The bioactive compounds in medicinal plants, their pharmacologic activity, and their potential to mitigate infectious diseases during epidemics and pandemics are presented in Table 1 and Figure 1.