Introduction

Bersama lucens (Hochst.) Szyszyl is a shrub to medium-sized tree belonging to the Francoaceae family. Under the Angiosperm Phylogeny Group iv classification system, the Melianthaceae family is included within the Francoaceae family (Group, 2016). The Francoaceae family consists of six genera, namely Balbisia Cav., Bersama Fresen., Francoa Cav., Greyia Hook. & Harv., Melianthus L. and Viviana Cav. The genus Bersama Fresen consists of shrubs and small trees recorded in the Afromontane vegetation, tropical lowland habitats and margins of evergreen forests in sub-Saharan Africa but conspicuously absent in the Congo basin (Decraene, Linder, Dlamini, & Smets, 2001; Linder, 2007). The recognized species include B. abyssinica Fresen., B. lucens, B. palustris L. Touss., B. swinnyi E. Phillips, B. swynnertonii Baker f., B. tysoniana Oliv, and B. yangambiensis L., Touss. Bersama lucens has been recorded in Eswatini, Mozambique and South Africa. The genus name Bersama refers to the Ethiopian name for this genus. The species name “lucens" is a Latin word meaning "shiny" or "polished" about the “glossy and shiny” leaves which are characteristic of the species. The synonyms of B. lucens include B. abyssinica Fresen., Natalia lucens Hochst., and Rhaganus lucidus E. Mey. The English common names of B. lucens include “glossy Bersama”, “glossy white ash” and “shiny-leaf Bersama”. Bersama lucens is a shrub or small tree with dense leaf clusters at the tips of the branchlets which grows to a height of 3 to 10 metres (Palgrave & Keith, 2002). The branchlets of B. lucens are grey to pale brown in colour, brittle, wrinkled bark with intrapetiolar stipules. The leaves are alternate, imparipinnate with hairless leaflets that are ovate to elliptic in shape, leathery, glossy bright green above with midrib and lateral veins that are yellowish and conspicuous on both surfaces. The leaflet tips are rounded or bluntly pointed with a tapering to rounded base, and the leaflet margins are thickened and usually waxy. The flowers are whitish or yellowish and occur on slender and erect racemes. The fruit is a wrinkled subglobose capsule with short hairs which is dull green when mature and splitting into four valves. The seeds are bright scarlet and partly enveloped in a green-yellowish, cup-shaped aril. Bersama lucens has been recorded in forest areas, riverine thickets, forest margins, bushveld, often in rocky places or on coastal dunes at an altitude ranging from 5 m to 1525 m above sea level.

The bark and roots of B. lucens and two other closely related species, B. swinnyi and tysoniana are regarded as significant sources of traditional medicines against headache, impotence, infertility, menstrual pain, nervous disorders, stroke and venereal diseases in South Africa (Hutchings, Scott, Lewis, & Cunningham, 1996; Wyk & Gericke, 2018). Based on their popularity as medicinal plants, these three species are included in the book "medicinal plants of South Africa," a monographic guide to the popular medicinal plants in the country, including their taxonomy, botanical description, primary medicinal uses, preparation and dosage, active phytochemical compounds and pharmacological effects (Wyk, Oudtshoorn, & Gericke, 2013). Moreover, the bark and roots of B. lucens are traded as herbal medicines in informal herbal medicine markets in about two-thirds of South African provinces, that is, Eastern Cape, Gauteng, KwaZulu-Natal, Mpumalanga, Northern Cape and Western Cape provinces (Dold & Cocks, 2002; Williams, Balkwill, & Witkowski, 2001). Therefore, this review aims to provide an overview of the medicinal uses, phytochemistry and pharmacological properties of B. lucens, and a critical review of the therapeutic potential of the species.

Materials and Methods

An extensive survey of literature related to the medicinal uses, phytochemistry and pharmacological properties of B. lucens was conducted using Science Direct, Pubmed, Google Scholar, Springer, Elsevier, NCBI, Taylor and Francis imprints, and review of books, journal articles and other scientific publications kept in the University library. The literature search was conducted using the following keywords: "Bersama lucens”, “medicinal uses of Bersama lucens”, “phytochemicals of Bersama lucens”, “biological activities of Bersama lucens”, “ethnobotany of Bersama lucens”, and various common names and synonyms of the species were also used as keywords to get additional information about the species.

Results and Discussion

Medicinal uses of Bersama lucens

The bark and root infusion or decoction of B. lucens are mainly used as a blood purifier, lice repellent and protective charm, and traditional medicine for stomach problems, leprosy, stroke, sexually transmitted infections (including venereal diseases), headache, infertility, nervous disorders, impotence and menstrual pain (Table 1; Figure 1). Other minor medicinal uses of B. lucens supported by at least one literature report include the use of the bark and root infusion or decoction to boost immunity (Monakisi, 2007), and traditional medicine for hiccough (Simon et al., 1991), meningitis (Monakisi, 2007), pain (McGaw et al., 1997), skin problems (Bhat, 2013) and tuberculosis (Monakisi, 2007).

Phytochemistry and pharmacological properties of Bersama lucens

The ethnobotanical data about B. lucens is centred around its utilization as herbal medicine. However, there is very little information available concerning the phytochemistry and pharmacological properties of the crude extracts or compounds isolated from the species. Pollard and Amuti (1981) identified small amounts of fructose oligosaccharides from the stems of B. lucens. Research by Cunningham (2001) revealed that the bark of B. lucens contains high amounts of calcium oxalate crystals. Koorbanally, Makatini, and Crouch (2008) identified triterpenoid compounds lup-30-al-3b-ol and lup-20-(30)-en-3,29-diol-7-one from the bark of B. lucens. Wyk et al. (2013) argued that B. lucens should be used caution as herbal medicine as related species such as B. abyssinica are known to contain poisonous heart glycosides such as melianthugenin. Some of these phytochemical compounds may be responsible for the pharmacological properties of the species.

Buwa (2006); Buwa et al. (2006) evaluated the antibacterial activities of water, ethyl acetate and ethanol extracts of B. lucens bark against Klebsiella pneumoniae ATCC 13883, Bacillus subtilis ATCC 6051, Staphylococcus aureus ATCC 12600 and Escherichia coli ATCC 11775 using the microplate method with neomycin as a positive control. The water and ethanol extracts exhibited activities against tested pathogens with minimum inhibitory concentration (MIC) values ranging from 3.1 mg/ml to >12.5 mg/ml (Buwa et al., 2006; Buwa, 2006). Khumalo (2018) evaluated the antibacterial activities of dichloromethane and methanol extracts of B. lucens bark against Bacillus cereus ATCC 11175, Enterococcus faecalis ATCC 29121, Escherichia coli ATCC 8739, Salmonella typhimurium ATCC 14028 and Shigella sonnei ATCC 9290 using the micro-titre plate technique with ciprofloxacin as a positive control. The extracts exhibited activities with MIC values ranging from 0.3 mg/ml to 2.0 mg/ml in comparison to MIC values of 0.02 μg/ml to 0.07 μg/ml exhibited by the positive control (Khumalo, 2018).

Buwa (2006); Buwa et al. (2006) evaluated the antifungal activities of water, ethyl acetate and ethanol extracts of B. lucens bark against Candida albicans ATCC 10231 using the microplate method with neomycin as a positive control. The extracts exhibited activities against the tested pathogen with MIC values ranging from 0.78 mg/ml to 12.5 mg/ml (Buwa et al., 2006; Buwa, 2006). McGaw et al. (1997) evaluated the anti-inflammatory activities of the aqueous and ethanol leaf extracts of B. lucens by assessing the inhibition of prostaglandin biosynthesis using the cyclooxygenase assay with indomethacin (0.5 µg) as a positive control. The extracts exhibited suitable activities with percentage inhibition ranging from 71.0% to 80.0%, which were higher than 75.0% exhibited by the positive control (McGaw et al., 1997).

Conclusions

Since toxic heart glycosides such as melianthugenin have been isolated from closely related B. abyssinica, there is, therefore, need for detailed clinical and toxicological evaluations of crude extracts and compounds isolated from B. lucens. Therefore, the widespread use of B. lucens as herbal medicine in southern Africa suggest that the species is not taken at toxic dosages. Therefore, the use of B. lucens for the treatment of human diseases and ailments should be treated with caution and rigorous toxicological and clinical studies of different plant parts used as traditional medicine are necessary.

Acknowledgement

I am grateful to the reviewers who kindly commented on my manuscript.

Funding Support

The authors declare that they have no funding support for this study.

Conflict Of Interest

The authors declare that they have no conflict of interest for this study.