INTRODUCTION
Baccharoides guineensis (Benth.) H. Rob. (Fig. 1) is a subshrub or perennial herb belonging to the Asteraceae or Compositae family. This species was originally treated under the genus Vernonia Schreb. (Isawumi et al., 1996), a genus confined to North America (Robinson et al., 2016). The genus name Baccharoides was first proposed by Moench in 1,793 and remained unused until it was resurrected by Robinson in 1990 (Robinson, 1999; Robinson et al., 2016). Baccharoides guineensis is a variable species with three recognized varieties based on the floral characteristics and geographical distribution. These varieties include the most widespread taxon, var. guineensis H. Rob., recorded in South Sudan, Central Africa Republic, Gabon, Guinea, Chad, Liberia, Ghana, Cameroon, Mali, Burkina Faso, Niger, Sierra Leone, Côte d’Ivoire, the Democratic Republic of Congo (DRC), Sudan, Togo, Angola, and Zambia; var. procera (O. Hoffm.) Isawumi, recorded in Benin and Nigeria; and var. cameroonica (C.D. Adams) Isawumi which is restricted to Cameroon. The synonyms associated with the name B. guineensis include Cacalia firma Kuntze, C. guineensis Kuntze, Vernonia chevalieri O. Hoffm., V. firma Oliv. & Hiern, V. guineensis Benth., V. hierniana S. Moore, V. procera O. Hoffm., V. rotundisquama S. Moore, V. ulophylla O. Hoffm., V. guineensis Benth. var. cameroonica C.D. Adams, V. guineensis Benth. var. guineensis, and V. guineensis Benth. var. procera (O. Hoffm.) C.D. Adams (Isawumi et al., 1996; Smith, 1971). Baccharoides guineensis has been recorded in variable habitats, ranging from high rainfall areas to open deciduous woodlands and savannas, grasslands, granite kopjes, and roadsides.
The Baccharoides genus is reported in the literature to have medicinal properties. For example, Baccharoides adoensis (Sch. ex Walp.) H. Rob., B. antheintica (L.) Moeh, and B. lasipus (O. Hofm.) H. Rob. are used in tropical Africa and India as ethnoveterinary medicine and traditional medicines for cough, diabetes, fever, gastrointestinal problems, malaria, sexually transmitted infections, tuberculosis, and wounds (Burkill, 1985; Hutchings et al., 1996; Toyang and Verpoorte, 2013). In countries such as Cameroon, the DRC, South Sudan, and Zambia, where B. adoensis, B. guineensis, and B. lasiopus have been recorded (Darbyshire et al., 2015; Dharani and Yenesew, 2010; Dharani et al., 2010; Dharani, 2019; Figueiredo and Smith, 2008; Friis and Vollesen, 1998; Neuwinger, 1996, 2000; Pope, 1992), there appear to be difficulties in identifying the species due to similar morphological characters. An ethnopharmacological research revealed that B. adoensis, B. anthelmintica, and B. lasiopus are characterized by antimicrobial, anthelmintic, antidiabetic, antioxidant, hepatoprotective, cytotoxicity, and antiplasmodial activities (Toyang and Verpoorte, 2013). Similarly, the tubers of B. guineensis are sold as traditional medicines by herbalists, informal traders, and hawkers in West Africa, particularly in Cameroon using the trade name Ginseng (Ngemenya et al., 2019; Toyang et al., 2012a; Toyang et al., 2013a; Wouamba et al., 2020). The common name Ginseng is based on the striking morphological resemblance between the carrot-like tubers or roots of B. guineensis and the roots of the popular medicinal plant species Panax ginseng C.A. Mey (family Araliaceae) and other Ginseng species (Toyang et al., 2012a). Moreover, a patent highlighting the chemotherapeutic activities of the phytochemical compounds isolated from the species against abnormal cell growth was registered about 10 years ago (Toyang et al., 2012b). It is, therefore, within this context that this investigation was undertaken aimed to document the pharmacological properties, phytochemistry, and medicinal uses of B. guineensis.
 | Figure 1. B. guineensis. (A) entire plant showing leaves and inflorescence, (B) leaf showing leaf serrations, and (C) inflorescence (photo: A Maroyi). [Click here to view] |
 | Figure 2. Flow diagram showing the literature search and selection processes. [Click here to view] |
MATERIALS AND METHODS
The results of this study are based on literature search on phytochemistry, pharmacological properties, and medicinal uses of B. guineensis using information derived from internet databases (Fig. 2), such as ScienceDirect, Google Scholar, PubMed, MEDLINE, and Scopus. Other sources of information included pre-electronic sources such as scientific publications, books, dissertations. and book chapters and other journal articles obtained from the university library.
RESULTS AND DISCUSSION
Medicinal uses of B. guineensis
The medicinal uses of B. guineensis have been recorded in Cameroon, Angola, Côte d’Ivoire, Nigeria, DRC, Ghana, Guinea, Sierra Leone, and Gabon representing 50% of the countries, where the species is indigenous. Major medicinal applications of B. guineensis, which have been recorded in three countries and supported by at least two literature records, include the use of the species as an anthelmintic, snakebite antidote, and ethnoveterinary medicine and as traditional medicine for toothache, gastrointestinal problems, jaundice, malaria, and female and male infertility (Table 1 and Fig. 3). The other medicinal uses of B. guineensis documented in two countries include the use of the extracts of the species as an aphrodisiac (Burkill, 1985; Iwu, 1993; Jiofack et al., 2009; Smith, 1971; Sobrinho et al., 2015) and purgative (Smith, 1971; Burkill, 1985) and as traditional medicine for hernia (Burkill, 1985; Göhre et al., 2016; Smith, 1971), urogenital disorders (Burkill, 1985; Focho et al., 2009b; Noumi and Ebwelle, 2011; Odugbemi, 2006), and sores and wounds (Burkill, 1985; Göhre et al., 2016; Yamada, 1999).
 | Table 1. Medicinal uses of B. guineensis. [Click here to view] |
Phytochemistry of B. guineensis
The compounds such as vernolepin and vernodalin have been identified from B. guineensis (Toubiana et al., 1975). Tchinda et al. (2002) identified vernoguinosterol and vernoguinoside peracetate from stembark of B. guineensis. Tchinda et al. (2003) identified vernoguinoside, 16β,22R;21,23S-diepoxy-21S,24-dihydroxy-5α-stigmasta-8,14-diene-3,28-dione, 1′,3,3′,4′,6′-pentakis-O-(3-methylbutanoyl)-β-D-fructofuranosyl α-D-glucopyranoside, and 1′,2,3′,6,6′-pentakis-O-(3-methylbutanoyl)-β-D-fructofuranosyl α-D-glucopyranoside from the stem bark of B. guineensis. Donfack et al. (2012) identified vernoguinoside, vernoguinoside A, stigmasterol 3-O-β-D-glucoside, and sitosterol 3-O-β-D-glucoside from the roots of B. guineensis. Toyang et al. (2013a) identified vernopicrin and vernomelitensin from the leaves of B. guineensis. Toyang et al. (2013b) identified pentaisovaleryl sucrose from the tubers of B. guineensis. Ditchou et al. (2019) identified the compounds such as betulinic acid, alphitolic acid, β-sitosterol 3-O-β-D-glucopyranoside, scoparone, and quercetin-3-O-β-galactoside from the roots of B. guineensis. Wouamba et al. (2020) identified vernoguinamide, physion, erythroglaucin, emodin, hop-17(21)-en-3β-yl acetate, lupeol, betulinic acid, vernoguinoside A, vernoguinoside, β-sitosterol 3-O-β-D-glucoside, stigmasterol 3-O-β-D-glucoside, stigmasterol, β-sitosterol, tetracosanoic acid, tricosanic acid, and arachidic acid glycerol ester from the roots of B. guineensis. Similar phytochemical compounds such as alkaloids, carbohydrates, chondrillasterol, flavonoids, free sugars, glaucolides, glycosides, phenols, proanthocyanidin, saponins, steroids, tannins, and terpenoids have been identified from a closely related species B. adoensis (Bohlmann et al., 1984; Deeni and Hussain, 1994; Ibrahim and Ogayi, 2012; Inngjerdingen et al., 2012; Mabhiza et al., 2016; Mozirandi et al., 2019; Muhindi et al., 2016; Sanogo et al., 1998; Swamy et al., 2013, 2014). Similarly, B. lasiopus yielded the elemanolide-type sesquiterpene lactones, alkaloids, anthraquinones, cardiac glycosides, coumarins, flavonoids, phenolics, reducing sugars, saponins, steroids, tannins, terpenoids, and xanthines (Chhabra et al., 1984; Kimani et al., 2017a, 2017b; Koul et al., 2003; Mutembei et al., 2018; Ochwang’i et al., 2016; Tarwish et al., 2017).
Pharmacological properties of B. guineensis
The following pharmacological activities have been documented from the leaves, roots, and/or tubers of B. guineensis, and the phytochemical compounds isolated from the species have anthelmintic, antiangiogenic, antibacterial, antifungal, antioxidant, antiplasmodial, antiproliferative, antitrypanosidal, and clonogenic activities.
Anthelmintic activities
Toyang et al. (2012c) evaluated the anthelmintic activities of dichloromethane, methanol, and water extracts from the leaves and tubers of B. guineensis using the larval and adult stages of the hookworm Ancylostoma ceylanicum and the mouse nematode Trichuris muris. The organic extracts of the tubers demonstrated activities, exhibiting 100% killing efficacy against T. muris at 2.0 mg/ml in 48 hours. The organic extracts of the leaves exhibited the activities killing 100% of the adult A. ceylanicum at 1.0 mg/ml in 24 hours, whereas the aqueous extract of the leaves was active at 2.0 mg/ml in 72 hours, killing 100% of the adult A. ceylanicum (Toyang et al., 2012c). Evaluation of the anthelmintic activities of the aqueous extracts of B. lasiopus leaves using the in vitro anthelmintic assay against the gastrointestinal nematode infective larvae of Haemonchus, Mecistocirrus, Ostertagia, Trichostrogylus, Cooperia, Bunostomum, and Oesophagostomum species exhibited moderate anthelmintic activities (Njonge et al., 2013).
 | Figure 3. Medicinal applications of B. guineensis derived from the literature records. [Click here to view] |
Antiangiogenic activities
Toyang et al. (2012a) evaluated the antiangiogenic activities of aqueous, dichloromethane, and methanol extracts of the tubers of B. guineensis and the compound pentaisovaleryl sucrose isolated from the tubers of the species against three prostate cancer cell lines (PC-3, DU-145 and AT3B-1) using the Sprague–Dawley rat ring aorta assay. The methanol and aqueous extracts inhibited the sprout formation in the rat ring aorta assay at 30 and 100 μg/ml (Toyang et al., 2012a).
Antibacterial activities
Donfack et al. (2012) evaluated the antibacterial activities of dichloromethane:methanol (1:1) extract of the roots of B. guineensis and the compounds such as vernoguinoside, vernoguinoside A, and stigmasterol 3-O-β-D-glucoside isolated from the roots of the species against Salmonella typhi, Staphylococcus aureus, and Shigella flexneri using the broth microdilution method with ciprofloxacin (1.0–62.5 μg/ml) as a positive control. The extract and compounds exhibited the activities against S. aureus and S. flexneri with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranging from 62.5 to 125.0 μg/ml in comparison to MIC and MBC values of 3.9–7.8 μg/ml exhibited by the positive control (Donfack et al., 2012). Toyang et al. (2012c) evaluated the antibacterial activities of dichloromethane, methanol, and water extracts of the leaves and tubers of B. guineensis against Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, S. aureus, and Staphylococcus epidermidis using microdilution assay with gentamicin as a positive control. The extracts exhibited weak activities against A. baumannii, S. aureus, and S. epidermidis with MIC values ranging from 750.0 to 1,000.0 μg/ml (Toyang et al., 2012c). Ditchou et al. (2019) evaluated the antibacterial activities of the compounds such as betulinic acid, alphitolic acid, β-sitosterol 3-O-β-D-glucopyranoside, scoparone, and quercetin-3-O-β-galactoside isolated from the roots of B. guineensis against Aerococcus viridans, E. coli, Klebsiella pneumoniae, Neisseria gonorrhoeae, P. aeruginosa, Salmonella choleraesuis, Proteus mirabilis, S. aureus, and Enterococcus faecalis using the microdilution method with ciprofloxacin and gentamicin as the positive controls. The compounds exhibited weak activities against A. viridans, S. choleraesuis, S. aureus, and E. faecalis with MIC and MBC values ranging from 312.5 to 2,500.0 μg/ml and 625.0 to 5,000.0 μg/ml, respectively (Ditchou et al., 2019). Wouamba et al. (2020) evaluated the antibacterial activities of the crude extract, ethyl acetate, and n-butanol fractions of the roots of B. guineensis and the compounds such as vernoguinamide, physion, erythroglaucin, emodin, hop-17(21)-en-3β-yl acetate, lupeol, betulinic acid, vernoguinoside A, vernoguinoside, β-sitosterol 3-O-β-D-glucoside, stigmasterol 3-O-β-D-glucoside, stigmasterol, β-sitosterol, tetracosanoic acid, tricosanic acid, and arachidic acid glycerol ester isolated from the roots of the species against E. coli, Salmonella enterica, and S. flexneri using the broth microdilution method with ciprofloxacin (7.8 μg/ml) as a positive control. The ethyl acetate and n-butanol fractions and the compounds exhibited activities against the tested pathogens with MIC values ranging from 31 to >500.0 μg/ml in comparison to MIC value of 0.07 μg/ml exhibited by the positive control (Wouamba et al., 2020).
Similar results were obtained by several researchers who evaluated the antibacterial activities of aqueous and organic extracts of B. adoensis and compounds isolated from the species against both Gram-negative and Gram-positive bacteria (Kisangau et al., 2007; Chitemerere and Mukanganyama, 2011; Ibrahim and Ogayi, 2012; Mutuku et al., 2013; Mozirandi and Mukanganyama, 2017). The leaf and stem extracts of B. lasiopus also exhibited the antibacterial activities against both Gram-negative and Gram-positive bacteria (Kareru et al., 2008; Mutembei et al., 2018; Rachuonyo et al., 2016a, 2016b, 2016c, 2016d, 2016e).
Antifungal activities
Donfack et al. (2012) evaluated the antifungal activities of dichloromethane:methanol (1:1) extract of the roots of B. guineensis and the compounds such as vernoguinoside, vernoguinoside A, and stigmasterol 3-O-β-D-glucoside isolated from the roots of the species against Candida albicans, Candida parapsilosis, and Cryptococcus neoformans using the broth microdilution method with nystatin (1.0–62.5 μg/ml) as a positive control. The extract and compounds exhibited the activities against tested pathogens with MIC and minimum fungicidal concentration (MFC) values ranging from 7.8 to 125.0 μg/ml in comparison to MIC and MFC values of 1.9–15.6 μg/ml exhibited by the positive control (Donfack et al., 2012). Toyang et al. (2012c) evaluated the antifungal activities of dichloromethane, methanol, and water extracts of the leaves and tubers of B. guineensis against Aspergillus fumigatus, C. albicans, C. neoformans, and Trichophyton mentagrophytes using microdilution assay with fluconazole and amphotericin B as the positive controls. The extracts exhibited weak activities against the tested pathogens with MIC values ranging from 200.0 to 1,000.0 μg/ml (Toyang et al., 2012c). Ditchou et al. (2019) evaluated the antifungal activities of the compounds such as betulinic acid, alphitolic acid, β-sitosterol 3-O-β-D-glucopyranoside, scoparone, and quercetin-3-O-β-galactoside isolated from the roots of B. guineensis against C. albicans using the microdilution method. Only compounds, such as alphitolic acid and β-sitosterol 3-O-β-D-glucopyranoside, exhibited the activities with the zone of inhibition of 7.0 mm (Ditchou et al., 2019). The crude leaf and stem extracts of a closely related species, B. lasiopus, exhibited the activities against C. albicans, Microsporum canis, and T. mentagrophytes (Rachuonyo et al., 2016a, 2016f; Vlietinck et al., 1995).
Antioxidant activities
Evans et al. (2015) evaluated the antioxidant activities of 80% methanol extracts of the leaves of B. guineensis using ferric reducing antioxidant power (FRAP) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays with ascorbic acid and trolox as the positive controls. The extract exhibited activities with FRAP value of 23.9 mg of TE/g of dry extract in comparison to 45.0 and 47.5 mg of TE/g of dry extract exhibited by the two positive controls. In the ABTS assay, the extract exhibited the activities with the percentage of inhibition of 67.0% and half-maximal inhibitory concentration (IC50) value of 13.1 μg/ml in comparison to the IC50 values of 4.1 and 4.9 μg/ml exhibited by the positive controls (Evans et al., 2015). Similarly, the aqueous and organic extracts of the leaves and roots of B. adoensis exhibited the antioxidant activities when evaluated using ABTS, FRAP, hydroxyl radicals, nitric oxide, and superoxide radicals scavenging ability assays (Mautsa and Mukanganyama, 2017; Nethengwe et al., 2012; Stangeland et al., 2010; Vasincu et al., 2014).
Antiplasmodial activity
Toyang et al. (2013b) evaluated the antiplasmodial activities of dichloromethane, methanol, and water extracts of the leaves and tubers of B. guineensis and the compounds such as vernopicrin, vernomelitensin, and pentaisovaleryl sucrose isolated from the leaves and tubers of the species against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum using an SYBR Green I-based DNA detection method with artesunate and chloroquine as the positive controls. The extracts and compounds exhibited activities with IC50 values ranging from 0.5 to 30.0 μg/ml in comparison to IC50 values of 0.002–0.07 μg/ml exhibited by the positive controls (Toyang et al., 2013b). The aqueous and organic extracts of the leaves of B. adoensis also exhibited antiplasmodial activities (Nethengwe et al., 2012; Obbo et al., 2019; Stangeland et al., 2010; Zemicheal and Mekonnen, 2018). The aqueous and organic extracts of B. lasiopus leaves as well as compounds isolated from the species exhibited antiplasmodial activities against chloroquine-sensitive and resistant P. falciparum (Irungu et al., 2007; Kimani et al., 2017b; Muregi et al., 2003; Muthaura et al., 2015; Njenga et al., 2015). The leaf, root, and stem bark extracts of B. lasiopus exhibited in vivo antimalarial activities in mice against a chloroquine-tolerant Plasmodium berghei (Muregi et al., 2007).
Antiproliferative activities
Toyang et al. (2012a) evaluated the antiproliferative activities of aqueous, dichloromethane, and methanol extracts of the tubers of B. guineensis and the compound such as pentaisovaleryl sucrose isolated from the tubers of the species against three prostate cancer cell lines (PC-3, DU-145 and AT3B-1) using the 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) assay. The extracts and the compound exhibited the activities with IC50 values ranging from 4.2 to >100.0 μg/ml (Toyang et al., 2012a). Toyang et al. (2013a) evaluated the antiproliferative activities of acetone extracts of the leaves of B. guineensis and the compounds such as vernopicrin and vernomelitensin isolated from the leaves of the species against 10 cancer cell lines (breast: MDA-MB-231, breast: MCF-7, colon: HCT-116, leukemia: HL-60, lung: A549, melanoma: A375, ovarian: OVCAR3, pancreas: Mia-paca, prostate: PC-3, and prostate: DU145) using the WST-1 assay. The extract exhibited the activities with IC50 values ranging from 4.0 to 26.0 μg/ml against the 10 cell lines, whereas the compounds exhibited IC50 values ranging from 0.1 to 2.0 μM (Toyang et al., 2013a). Toyang et al. (2013c) evaluated the antiproliferative activities of dichloromethane extracts and the compound pentaisovaleryl sucrose isolated from the tubers of B. guineensis using in vivo antiprostate tumor assay in nude mice, in vitro using the WST-1 assay against nine cancer cell lines (breast: MDA-MB231, breast: MCF-7, colon: HCT-116, leukemia: HL-60, lung: A549, melanoma: A375, ovarian: OVCAR3, pancreatic: Mia-Paca, and prostate cancer: CAPAN-1). The prostate cancer (PC-3) xenograft tumors treated with the extract showed the activities by decreasing the tumor size, whereas the compound also demonstrated activities by exhibiting IC50 values ranging from 5.0 to 14.1 μM (Toyang et al., 2013c). Toyang (2014) evaluated the antiproliferative activities of dichloromethane extracts of the root tubers of B. guineensis against the prostate cancer line (PC-3) using trypan blue cell viability assay. The extract inhibited greater than 50% of cell viability at the concentrations of <40.0 μg/ml (Toyang, 2014).
Antitrypanosidal activities
Tchinda et al. (2002) evaluated the antitrypanosidal activities of the compounds such as vernoguinosterol and vernoguinoside peracetate isolated from the stem bark of B. guineensis against the four strains of bloodstream trypomastigotes Trypanosoma brucei rhodesiense using the Alamar Blue assay. The compounds exhibited the inhibitory activities with IC50 values ranging from 3. to 5.0 μg/ml (Tchinda et al., 2002). Kimani et al. (2017a, 2017b) evaluated the in vitro antitrypanosomal activities of the aqueous and organic of the aerial parts of B. lasiopus and phytochemical compounds isolated from the species using Almar Blue and resazurin assay. Both the extract and the compounds exhibited the activities with the IC50 values ranging from 0.2 to 65.8 μg/ml for the extracts and 0.07–9.8 μM for the compounds (Kimani et al., 2017a, 2017b).
Clonogenic activities
Toyang et al. (2012a) evaluated the clonogenic activities of aqueous, dichloromethane, and methanol extracts of the tubers of B. guineensis and the compound pentaisovaleryl sucrose isolated from the tubers of the species against the prostate cancer cell lines (PC-3) using the clonogenic assay. The extracts and the compound exhibited dose-dependent activities by inhibiting the colony formation by PC-3 cells (Toyang et al., 2012a). Toyang et al. (2013a) evaluated the clonogenic activities of acetone extracts of the leaves of B. guineensis and the compounds such as vernopicrin and vernomelitensin isolated from the leaves of the species against 10 cancer cell lines (breast: MDA-MB-231, breast: MCF-7, colon: HCT-116, leukemia: HL-60, lung: A549, melanoma: A375, ovarian: OVCAR3, pancreas: Mia-paca, prostate: PC-3, and prostate: DU145) using the clonogenic assay. The extract and the compounds exhibited dose-dependent activities inhibiting the colony formation with an IC50 value of <0.5 μM (Toyang et al., 2013a).
CONCLUSION
Research conducted so far revealed that compounds such as alphitolic acid, arachidic acid, betulinic acid, emodin, erythroglaucin, hop-17(21)-en-3β-yl acetate, lupeol, pentaisovaleryl sucrose, physion, quercetin-3-O-β-galactoside, scoparone, β-sitosterol 3-O-β-D-glucopyranoside, stigmasterol, stigmasterol 3-O-β-D-glucoside, tetracosanoic acid, tricosanic acid, vernoguinamide, vernoguinoside, vernoguinoside A, vernoguinosterol, vernoguinoside peracetate, vernopicrin, and vernomelitensin isolated from B. guineensis have antiangiogenic, antibacterial, antifungal, antitrypanosidal, and clonogenic activities. Therefore, the future research on B. guineensis should focus on the possible biochemical mechanisms of both the crude extracts and identified phytochemical compounds including the toxicological, in vivo, and clinical studies to corroborate the traditional medical applications of the species.
CONFLICT OF INTEREST
The author declares that he has no conflict of interest.
FUNDING
None.
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