**2.2** *Artemisia afra*

*Artemisia afra* (**Figure 3**)*,* also known as African wormwood, belongs to the *Asteraceae* family [44, 45]. It is indigenous to Africa and is widely distributed in South Africa, Namibia, Zimbabwe, Kenya, Tanzania, Uganda, and Ethiopia [30, 44]. *Artemisia afra* is called Umhlonyane in Xhosa and Lengana in Sesotho [44]. It is used traditionally for the treatment of respiratory symptoms and diseases including cold, cough, headache, influenza, sore throat, asthma, and pneumonia (**Table 1**), and other disease conditions such as diabetes, colic, dyspepsia, bladder and kidney disorders,

*Traditional Medicinal Plants as the Potential Adjuvant, Prophylactic and Treatment Therapy… DOI: http://dx.doi.org/10.5772/intechopen.104491*


#### **Table 2.**

*Secondary metabolites of TMPs with adjuvant, prophylactic, and anti-COVID-19 activity.*

constipation, malaria, and rheumatism [30, 31]. *Artemisia afra* contains secondary metabolites including tannins, alkaloids, terpenoids, cardiac glycosides, and saponins [30]. Pharmacological activities of *Artemisia afra* include antioxidant, antiviral, antiplamodial, antifungal, and antibacterial [30, 31, 44]. *Artemisia afra* aqueous and ethanolic extracts, as well as teas, were shown to inhibit SARS-CoV-2 plaque formation *in vitro* [15]. The antiviral activity of this medicinal plant is reported to have been as a result of flavonoids present in *Artemisia* species (**Table 2**) [15]. The extracts showed some toxicity at higher concentrations with the selectivity index of 10, which opened a therapeutic window that is required to be further investigated in clinical trial [15]. There is still a need to prove whether *Artemisia afra* extracts can reach the serum levels required to completely inhibit the virus in COVID-19 patients.

#### **2.3** *Aspalathus linearis*

*A. linearis* (**Figure 4**), also known as Rooibos in Afrikaans, belongs to the *Fabaceae* family and is an endemic South African species cultivated to produce a tea [46–48]. It is used commonly for the treatment of respiratory disease such as asthma (**Table 1**) and other diseases including cardiac arrhythmias, colic, diarrhea, and hypertension [32]. Rooibos contains flavonoids including aspalathin, isoorientin,

**Figure 3.** Artemisia afra *leaves.*

**Figure 4.** *Aspalathus linearis.*

isovitexin, nothofagin, orientin, quercetin, rutin, and vitexin [41]. Other present secondary metabolites include polyphenols and phenolic compounds such as dihydro-chalcones, flavonols, flavonones, and proanthocyanadins [41, 46, 47]. Rooibos has pharmacological activities including antioxidant, antiviral, immunomodulatory, anti-inflammatory, cardioprotective, and nephroprotective effects [41]. Flavonoids, quercetin, and luteolin (**Table 2**) present in Rooibos were found to inhibit SARS-CoV infection by preventing entry of virus into E6 cells, and luteolin acts by binding to SARS-CoV S proteins, thereby interfering with the S protein function [41]. However, more experiments must be conducted to validate the clinical relevance of Rooibos in treating COVID-19 and other respiratory diseases [41]. Although other studies have highlighted the drug interactions associated with the

*Traditional Medicinal Plants as the Potential Adjuvant, Prophylactic and Treatment Therapy… DOI: http://dx.doi.org/10.5772/intechopen.104491*

Rooibos derived phytochemicals [42], more research is required in determining the safety of Rooibos in patients.

#### **2.4** *Clerodendrum splendens*

*Clerodendrum splendens* (**Figure 5**), also known as bag flower, bleeding-heart, and glory bower in English [33, 49], belongs to the *Lamiaceae* family of plants [20]. It is distributed in tropical Africa, Southern Asia, America, and Northern Australasia [33]. *Clerodendrum splendens* is used traditionally to treat respiratory diseases such as asthma and coughs (**Table 1**) and other diseases including anorexia, leucoderma, leprosy, malaria, skin diseases, ulcers, uterine fibroids, wounds, burns, and sexually transmitted diseases such as syphilis and gonorrhea [20, 33]. Phytochemical constituents present in *Clerodendrum splendens* include alkaloids, cyanogenic glycosides, diterpenes, flavonoids, phenolic compounds, saponins, steroids, tannins, terpenoids, and volatile compounds [17, 20]. It has pharmacological activities including antibacterial, antifungal, anti-inflammatory, antiproliferative, antioxidant, and hepatoprotective [17, 20, 33]. *Clerodendrum splendens* contains a polysaccharide, type II arabinogalactam (**Table 2**), that has been shown to have immunomodulatory activity both *in vitro and in vivo* [17, 20]. Its antiproliferative activity is reported to be as a result of clerodane diterpenes and phenyl propanoids found in aerial parts this plant [17]. The methanol extract of *Clerodendrum splendens* was reported to have *in vitro* anti-inflammatory activity (**Table 2**) [24]. The findings reported on *Clerodendrum splendens* form the basis for further research into the efficacy and safety of this plant as potential COVID-19 treatment and anti-inflammatory agents [17, 24].

### **2.5** *Dioscorea batatas* **decne**

*D. batatas* decne (**Figure 6**), commonly called Chinese yam [50, 51], belongs to the *Dioscoreaceae* family of plants [21, 52]. *Dioscoreaceae* plant species are widely distributed in West Africa, Southeast Asia, and Tropical America [52]. *D. batatas* decne is used traditionally for the treatment of respiratory disease such as

**Figure 5.** Clerodendrum splendens *leaves and flowers.*

#### **Figure 6.** Dioscorea batatas *decne leaves and fruits.*

asthma (**Table 1**) and other conditions including, abscesses, cancer, inflammation, hypertension, ulcer, chronic diarrhea, and diabetes [21]. It has antioxidant and anti-inflammatory activities [22, 50]. *D. batatas* decne contains various active components, such as allantoin, batatasins, choline, dioscorin, diosgenin, gracillin, glycoproteins, L-arginine, mucopolysaccharides, prosapogenin, protein, polysaccharides, and sapogenins (**Table 2**) with immunomodulation effects when orally administered [17, 21, 22]. The immunomodulatory activity of tuber protein and dioscorin occurs through the activation of TLR4-induced macrophage due to the stimulation of signaling molecules such as NF-kB, JNK, p38, and ERK, and by TNF-a and IL-6 cytokines expression [17, 21, 22]. The immunomodulation effect of tuber extract on inflamed and normal skin was reported to be due to the enhancement of granulocyte-macrophage colony-stimulating factor promoter [17]. The tuber extract of *D. batatas* was found to be the potent inhibitor of SARS-CoV (**Table 2**) at concentrations between 25 and 200 μg/mL [53].
