Table 2.
Scientific evaluations of the inhibitory activity of southern African plants against viral respiratory pathogens.
| Plant Species | Common Name | Family | Plant Part Used | Formulation | Results | Reference |
|---|---|---|---|---|---|---|
| Acokanthera schimperi (A.DC.) Schweinf. | Unknown | Apocynaceae | Leaves | Multiple solvent extracts were tested. | Inhibited 50% parainfluenza production at a 1 in 10 dilution. | Bagla et al. (2012) |
| Aspalathus linearis (Burm.f.) R.Dahlgren | Red bush, bush tea (English), Rooibos (Afrikaans) | Fabaceae | Leaves | Leaf infusions | An IC50 value was not reported. Instead, the authors state that the extract inhibited influenza virus A and B production by 50% at 0.2% of the extract concentration (not stated in that study). | Rahmasaria et al. (2017) |
| Barleria prionitis L. subsp. delagoensis (Oberm.) Brummitt & J.R.I.Wood | Delagoa Bay barleria, porcupine flower (English) | Acanthaceae | Whole plant | DCM extract | Compounds isolated from the extract (6-O-transp-coumaroyl-8-O-acetylshanzhiside methyl ester and its cis isomer) inhibited syncytial virus (RSV) production (EC50 = 2.5 μg/mL) | Chen et al. (1998) |
| Burkea africana Hook. | Wild syringa (English) | Fabaceae | Bark | Purified saponins | Bark extracts displayed apparent antiviral activity in a cytopathic effect (CPE) assay. Eight individual saponins purified from the bark were potent inhibitors of H3N2 influenza Hong Kong strain, with IC50 values 0.05–0.27 μM. | Mair et al. (2018) |
| Carissa spinarum L. | Climbing num-num, small num-num (English), enkeldoringnoemnoem, ranknoemnoem, kleinnoemnoem (Afrikaans), mothokolo (Sotho) | Apocynaceae | Leaves | Multiple solvent extracts were tested. | Inhibited 25% parainfluenza production at a 1 in 10 dilution. | Bagla et al. (2012) |
| Clerodendrum glabrum E.Mey. var. glabrum | Tinderwood (English), tontelhout (Afrikaans), moswaapeba (Sotho), munukha-tshilongwe (Venda), umqwaqwanam (Xhosa), umQoqonga (Zulu) | Lamiaceae | Leaves | Methanol extract | Tested against influenza virus A. EC50 values of 110 μg/mL against both pre- and post-penetration phases of viral replication. Solvent extracts were substantially more potent than aqueous extracts. No direct interaction with viral hemagglutuinin glycoprotein. | Mehrbod et al. (2018) |
| Crassula globularioides subsp. argyrophylla (Diels ex Schönland & Baker f.) Toelken | Unknown | Crassulaceae | Aerial parts | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >6 μg/mL. | Beuscher et al. (1994) |
| Cussonia spicata Thunb. | Cabbage-tree (English), kiepersol (Afrikaans), umsenge(Zulu and Xhosa), motshetshe (Sotho) | Araliaceae | Leaves | Methanol extract | Tested against influenza virus A. EC50 values of 5–15 μg/mL against both pre- and post-penetration phases of viral replication. Solvent extracts were substantially more potent than aqueous extracts. No direct interaction with viral hemagglutuinin glycoprotein. | Mehrbod et al. (2018) |
| Ekebergia capenses Sparm. | Cape ash (English), essenhout (Afrikaans), mmidibidibi (Northern Sotho), umnyamathi (Zulu) | Meliaceae | Bark | Extracted with multiple solvents of varying polarity | Inhibited 75% parainfluenza production at a 1 in 10 dilution. | Bagla et al. (2012) |
| Helichrysum armenium DC | Unknown | Asteraceae | Leaves | Aqueous and ethanolic extracts | Inhibited parainfluenza virus production. MIC = 4 μg/mL | Kutluk et al. (2018) |
| Helichrysum melanacme DC. | Hotnotskooigoed (Afrikaans) | Asteraceae | Leaves | Ethanol extract | Inhibited influenza virus A production. IC50 = 10 μg/mL | Lall et al. (2006) |
| Heteromorpha arborescens (Spreng.) Cham. & Schltdl. | Parsley tree (English), wildepietersielie (Afrikaans) | Apiaceae | Root bark | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >25 μg/mL. | Beuscher et al. (1994) |
| Holarrhena pubescens Wall. ex G. Don | Fever-pod (English) Jasmine-tree (English) | Apocynaceae | Bark | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >10 μg/mL. | Beuscher et al. (1994) |
| Jasminum fluminense Vell. | River jasmine (English), rivier jasmyn (Afikaans) | Olacaceae | Stems | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >50 μg/mL. | Beuscher et al. (1994) |
| Pelargonium sidoides DC. | Black pelargonium, South African geranium (English), kalwerbossie, rabassam (Afrikaans), ikubalo, iyeza lesikhali (Xhosa), khoara-e-nyenyane (Southern Sotho | Geraniaceae | Unspecified | A proprietary preparation named EPs 7630 was tested. | EPs 7360 at a concentration of 100 μg/mL inhibited the replication of H1N1and H3N2 influenza virus, parainfluenza virus, HRSV and human coronavirus strain 229E, but did not affect H5N1 influenza strain, or several adenoviruses and rhinoviruses. | Michaelis et al. (2011) |
| Pittosporum viridiflorum Sm. | Cheesewood (English), kasuur (Afrikaans), kgalagangwe (Northern Sotho), umkhwenkhwe (Zhosa, Zulu), umfusamvu (Zulu) | Pittosporaceae | Leaf | Aqueous, methanol, ethanol and acetone extracts | Tested against influenza virus A. EC50 values of 3–82 μg/mL against both pre- and post-penetration phases of viral replication. Solvent extracts were substantially more potent than aqueous extracts. No direct interaction with viral hemagglutuinin glycoprotein. | Mehrbod et al. (2018) |
| Polygala lancifolia A. St. -Hil. & Moq. | Purple broom (English), persboom, bloukappie (Afrikaans), hlokoa leleue (Sotho), ithethe (Zulu) | Polygalaceae | Aerial parts | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >12 μg/mL. | Beuscher et al. (1994) |
| Pterocarpus angolensis DC. | Bloodwood, paddle-wood, sealing-wax tree, wild teak, Transvaal teak (English), bloedhout, dolfhout, greinhout, kajatenhout, lakhout, wilde-kiaat (Afrikaans), morôtô (Sotho), umvangazi, umbilo (Zulu) | Fabaceae | Bark | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >12 μg/mL. | Beuscher et al. (1994) |
| Rapanea melanophloeos (L.) Mez. | Cape beech (English); boekenhout, beukehout (Afrikaans), isiCalabi, umaPhipha, iKhubalwane, isiQalaba sehlati (Zulu), isiQwane sehlati (Xhosa) | Primulaceae | Leaves and twigs | Aqueous, methanol, ethanol and acetone extracts | Tested against influenza virus A. EC50 values of 113 μg/mL against both pre- and post-penetration phases of viral replication. No direct interaction with viral hemagglutuinin glycoprotein. | Mehrbod et al. (2018) |
| Steganotaenia araliacea Hochest. | Carrot tree (English) | Apiaceae | Root | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >5 μg/mL. | Beuscher et al. (1994) |
| Tabernaemontana ventricosa Hochst. ex. A.DC. | Forest toad tree (English), bospaddaboom (Afrikaans), uKhamamasane (Zulu) | Apocynaceae | Leaves | Extracted with multiple solvents of varying polarity | Tested against influenza virus A. EC50 values of 0.05 μg/mL against both pre- and post-penetration phases of viral replication. Solvent extracts were substantially more potent than aqueous extracts. No direct interaction with viral hemagglutuinin glycoprotein. | Mehrbod et al. (2018) |
| Xanthocercis zambesiaca (Baker) Dumaz-le-Grand | Nyala tree (English), njalaboom, hoenderspoor (Afrikaans), mutshato (Venda) | Fabaceae | Leaves | Methanol and DCM extracts | DCM extract strongly inhibited rhinovirus type 2 production in HeLa cells at concentrations >60 μg/mL. | Beuscher et al. (1994) |