This article followed all ethical standards for research without direct contact with human or animal subjects. No ethical clearance is required as this research used secondary data and literature reviews or published data.

Pseudarthria hookeri Wight & Arn. is a member of the Fabaceae, Leguminosae or legume, bean or pea family. The genus Pseudarthria Wight & Arn. consists of perennial, erect to suberect, woody herbs, shrubs or subshrubs arising from a thick rhizomatous and woody rootstock (Leistner 2000). The genus has been recorded in Asia, tropical Africa, Réunion island, Mauritius and Madagascar with about six species (Leistner 2000; Schrire 1988; Verdcourt 1971, 2000; Zhang, Yi1 & Pan 2018). The genus name ‘Pseudarthria’ is derived from two Greek words ‘pseudes’ which means ‘false’ and ‘arthria’ which means ‘joint’, in reference to the imperfectly segmented fruits (Manning 2009). The species name ‘hookeri’ is in honour of Sir William Jackson Hooker (1785–1865), an English botanist and botanical illustrator who was the first director of the Royal Botanical Gardens at Kew in the United Kingdom (Schmidt, Lotter & McCleland 2017). The synonyms associated with the botanical name P. hookeri Wight & Arn. include Anarthrosyne densiflora Klotzsch, Anarthrosyne robusta E. Mey., Desmodium kerstenii O. Hoffm., D. robustum E. Mey., Pseudarthria alba A. Chev., P. densiflora (Klotzsch.) B. D. Jacks and P. robusta (E. Mey.) Schltr. (Schrire 1988; Verdcourt 1971, 2000; Zhang et al. 2018). Accepted infraspecific taxa within P. hookeri are P. hookeri var. argyrophylla Verdc. and P. hookeri var. hookeri (Schrire 1988; Verdcourt 1971, 2000). The English common names of P. hookeri include ‘bug-catcher’, ‘pink velvet bean’ and ‘velvet bean’ (Gumede 2021; Manning 2009, 2012).

Pseudarthria hookeri is an erect, slender or arching deciduous shrub growing from a thick rhizome, with short-lived, erect-ascending velvety, angular and hairy stems, which branch from about halfway up, with grooved or strongly ribbed branches, growing up to 3 m in height (Manning 2012). The leaves of P. hookeri are alternate, petiolate, trifoliolate, terminal leaflet the largest, widely ovate to obovate elliptic, tips tapering, margins finely toothed, rough and green above and pale and velvety beneath. The curved, velvety hairs on leaves and stems act like velcro, sticking to other surfaces (Manning 2012). The flowers occur in copious terminal panicles or branched racemes, bright pink in colour, and calyx is velvety-brown or mauve in colour (Figure 1). The pods are oblong in shape, woody, straight, jointed but not breaking into segments, brown in colour, finely hairy, slightly constricted between the seeds. Pseudarthria hookeri has been recorded in Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, the Democratic Republic of Congo (DRC), Eswatini, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Kenya, Madagascar, Malawi, Mali, Mauritius, Mozambique, Nigeria, Rwanda, Senegal, Siera Leone, South Africa, South Sudan, Sudan, Tanzania, Togo, Uganda, Zambia and Zimbabwe (Burrows & Willis 2005; Burrows et al. 2018; Figueiredo & Smith 2008; Fischer et al. 2010; Germishuizen & Meyer 2003; Gosline et al. 2023; Loffler & Loffler 2005; Schrire 1988) (Figure 3). The species has been recorded in open woodland, savanna, often in rocky places, scrub, bushveld, upland and lowland grassland, bushed and wooded grassland on sandy soils at an altitude ranging from sea level to 2000 m above sea level (Burrows & Willis 2005; Loffler & Loffler 2005; Manning 2012; Schrire 1988; Wild et al. 1972). Ecological assessments, however, showed that P. hookeri is also a common weed or ruderal, particularly in old cultivation, abandoned agricultural fields, forest margins, disturbed areas, along rivers and streambanks, swampy areas and vleis (Manning 2012; Schrire 1988; Wild et al. 1972). In the field, P. hookeri is easily confused with Flemingia grahamiana Wight & Arn. (family Fabaceae), but F. grahamiana lacks the prominent striated stems and short stalk of the terminal leaflet (Schmidt et al. 2017).

Pseudarthria hookeri is used as a source of traditional medicines in Burundi, Cameroon, Eswatini, Ethiopia, Ivory Coast, Kenya, Nigeria, South Africa, Uganda and Zimbabwe, representing 29.4% of the countries where the species is indigenous (Table 1). Traditional medicines prepared from the fruits, leaves, roots and stems of P. hookeri are used to treat and/or manage 35 human and animal diseases and ailments (Table 1). The main diseases and ailments treated by P. hookeri extracts include reproductive problems, malaria, gastro-intestinal problems, respiratory infections, liver and skin problems (Table 1). In Zimbabwe, the root decoctions of P. hookeri are taken orally mixed with Arachis hypogea L. (family Fabaceae) as remedy for diarrhoea (Gelfand et al. 1985). Similarly, in Uganda, the leaf decoctions of P. hookeri are taken orally mixed with Cajanus cajan (L.) Huth (family Fabaceae) as remedy for diarrhoea (Namukobe et al. 2011). Similar observations have been made by Van Vuuren, Motlhatlego and Netshia (2022) who argued that combining of medicinal plants is common in the African herbal pharmacopoeia but very little research has been conducted aimed at scientifically validating the different types of herbal medicine combinations being used in the continent.

Leaves and other parts of P. hookeri are characterised by several classes of flavonoids such as flavanones, flavones and isoflavones (Table 2). Some of the chemical compounds isolated from P. hookeri whole plants include acetate, anthraquinone, coumaronochromones, ether, oligothiophene and phenolic acid (Dzoyem et al. 2018; Tchamgoue et al. 2016). In addition to flavonoids, Yaya et al. (2023) isolated alkaloids, including catechic tannins, polyphenols, polyterpenes, quinones, saponosides and sterols from P. hookeri leaves. Pseudarthria hookeri crude extracts and some flavonoids isolated from the species demonstrated pharmacological activities such as anti-anaemic, antibacterial, antifungal, antidiabetic, antioxidant, antiplasmodial, antiproliferative, antischistosomal, oestrogenic and larvicidal properties.

Yaya et al. (2023) evaluated the anti-anaemic activities of aqueous extract of P. hookeri leaves against phenylhydrazine-induced anaemic rats at doses of 50.0 mg/kg bw, 200.0 mg/kg bw, 1000.0 mg/kg bw and 2000 mg/kg bw with ranferon^® as a positive control. The extract exhibited activities by causing increase in haemoglobin, red blood cell and haematocrit levels, and the effects were similar to those exhibited by the positive control, ranferon^®, a pharmaceutical drug used for the treatment of anaemia (Yaya et al. 2023).

Asiimwe (2015) evaluated the antibacterial activities of ethanol extract of P. hookeri leaves against Staphylococcus aureus (ATCC 25923) and Streptococcus pneumoniae (ATCC 49619) using agar diffusion assay with ciprofloxacin as a positive control. The extract exhibited activities against the tested pathogens with zone of inhibition of 12.0 mm (Asiimwe 2015). Similarly, Dzoyem et al. (2018) evaluated the antibacterial activities of the flavonoids pseudarflavone A, 6,7-(2″,2″-dimethylchromano) flavanone, 6-prenylpinocembrin and desmoxyphyllin A isolated from the whole plants of P. hookeri against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus using broth microdilution assay with ciprofloxacin as a positive control. The flavonoids exhibited activities against the tested pathogens with minimum inhibitory concentration (MIC) values ranging from 4.0 µg/mL to 64.0 µg/mL (Dzoyem et al. 2018). These antibacterial properties exhibited by the crude extracts of P. hookeri and flavonoids isolated from the species support the traditional uses of the species against gastro-intestinal problems (Asiimwe et al. 2013; Gelfand et al. 1985; Gumede 2021; Gumisiriza et al. 2019; Kamatenesi-Mugisha et al. 2014; Kigen et al. 2016; Lye et al. 2008), respiratory problems (Asiimwe et al. 2013; Auerbach et al. 2012; Gumede 2021; Koné et al. 2004, 2005, 2007; Namukobe et al. 2011), syphilis (Ssegawa & Kasenene 2007b) and wounds (Auerbach et al. 2012).

Asiimwe (2015) evaluated the antifungal activities of ethanol extract of P. hookeri leaves against Candida albicans (ATCC 10231) using agar diffusion assay with nystatin as a positive control. The extract exhibited activities against the tested pathogen with zone of inhibition of 8.0 mm (Asiimwe 2015). These preliminary ethnopharmacological findings corroborate the traditional use of leaf or root decoctions of P. hookeri against skin problems such as purulent rashes (Ngezahayo et al. 2015), ringworm (Lye et al. 2008; Ngezahayo et al. 2015; Tabuti et al. 2003) and scabies (Lye et al. 2008).

Kahou et al. (2016) evaluated the antidiabetic activities of aqueous extract of P. hookeri leaves on haemoglobin glycation in diabetic Wistar rats. The extract administered orally at doses of 1000.0 mg/kg bw and 1200.0 mg/kg bw for 28 days caused a decrease in blood glucose, triglycerides and serum total cholesterol levels in diabetic rats (Kahou et al. 2016). Similarly, Tchamgoue et al. (2016) evaluated the insulin secretory activities of the flavonoids pseudarflavones A, 6,7-(2”,2”-dimethylchromano) flavanone, gancaonin P, boeravinone L, dorsamin F, dorsmanin I, 6-prenyl-30 -methoxyeriodictyol and orobol isolated from P. hookeri whole plants on isolated in vitro mice islets. The flavonoids exhibited mild to moderate insulin secretory activities (Tchamgoue et al. 2016). The antidiabetic and insulin secretory activities exhibited by the P. hookeri crude extracts and flavonoids isolated from the species support the traditional use of leaf decoctions as remedies for diabetes (Kahou et al. 2016).

Asiimwe (2015) evaluated the antioxidant activities of ethanol extract of P. hookeri leaves against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. The extract exhibited weak antioxidant activities of 43.7% (Asiimwe 2015). A species exhibiting antioxidant activities has the capacity to protect human body cells from harmful damage caused by free radicals.

Clarkson et al. (2004) evaluated the antiplasmodial activities of dichloromethane and methanol (1:1) extracts of P. hookeri leaves against chloroquine-sensitive strain (D10) of Plasmodium falciparum using the parasite lactate dehydrogenase (pLDH) assay with chloroquine diphosphate as a positive control. The extract exhibited activities with half maximal inhibitory concentration (IC₅₀) value of 100.0 µg/mL (Clarkson et al. 2004). Tchamgoue et al. (2022) evaluated the in vivo antiplasmodial activities of ethanol extract of P. hookeri leaves and the flavonoids quercetin, 7-O-benzyl-6-prenylpinocembrin and 6,8-diprenyleriodictyol isolated from the species against male Swiss albino mice infected with Plasmodium berghei. The ethanol extract exhibited activities causing 32.5% suppression at 500.0 mg/kg bw and prolonged the survival period of infected mice while similar activities were also exhibited by the flavonoids quercetin, 7-O-benzyl-6-prenylpinocembrin and 6,8-diprenyleriodictyol (Tchamgoue et al. 2022). Pseudarthria hookeri leaves are widely used as herbal medicines for malaria in Uganda (Anywar et al. 2016; Katuura et al. 2007; Lye et al. 2008; Ssegawa & Kasenene 2007a; Stangeland et al. 2011) and the documented antiplasmodial activities exhibited by both the crude extracts and flavonoids isolated from the species would contribute to the search for phytochemical compounds that could be used in the development of antimalarial drugs.

Dzoyem et al. (2018) evaluated the antiproliferative activities of the flavonoids pseudarflavone A, 6,7-(2″,2″-dimethylchromano) flavanone, 6-prenylpinocembrin, boeravinone L, desmoxyphyllin A and 7-benzyloxy-6-prenylpinocembrin isolated from the whole plants of P. hookeri against the human T-Cell leukaemia cells Jurkat cancer cells using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) colorimetric assay with doxorubicin as a positive control. The flavonoids showed activities exhibiting IC₅₀ values ranging from 3.6 µg/mL to 10.0 µg/mL (Dzoyem et al. 2018). The antiproliferative activities exhibited by the flavonoids isolated from P. hookeri corroborate the traditional uses of the species as remedy for breast cancer (Kudamba et al. 2023).

Sparg, Van Staden and Jäger (2000) assessed the antischistosomal activities of aqueous extracts of P. hookeri leaves against the schistosomula of Schistosoma haematobium with praziquantel as a positive control. The extract exhibited activities by killing 67.7% of the schistosomula worms at a concentration of 50.0 mg/mL after 12 to 24 h of exposure (Sparg et al. 2000). These results support the traditional uses of leaf and root decoctions of P. hookeri as remedy for bilharzia in Zimbabwe (Gelfand et al. 1985).

Vollmer and Njamen (2007) and Njamen et al. (2008) evaluated in vitro and in vivo oestrogenic activities of methanol extracts of P. hookeri roots. The in vitro and in vivo oestrogenic activities were screened using the yeast estrogen receptor assay, ovariectomised Wistar rats and alkaline phosphatase induction assay on Ishikawa cells. The extracts exhibited oestrogenic activities showing stimulating effects (Njamen et al. 2008; Vollmer & Njamen 2007). These preliminary results can be used as baseline data for further oestrogenic studies considering the fact that P. hookeri is used against female reproductive problems such as infertility (Lye et al. 2008), menstrual problems (Kamatenesi-Mugisha et al. 2007; Lye et al. 2008), prolapsed uterus (Kamatenesi-Mugisha et al. 2007; Lye et al. 2008), inducing labour (Lye et al. 2008; Tabuti et al. 2003) and retained placenta (Lye et al. 2008; Tabuti et al. 2003).

Koné et al. (2005) evaluated the larvicidal activities of ethanol extracts of P. hookeri leaves and roots against Haemonchus contortus using fenbendazole and ivermectin as positive controls. Both extracts showed activities exhibiting an absolute lethal concentration (LC₁₀₀) value of 0.8 mg/mL (Koné et al. 2005). Therefore, this species has potential to be used in the treatment of intestinal helminthosis.