A REVIEW OF BOTANY, MEDICINAL USES, AND BIOLOGICAL ACTIVITIES OF PENTANISIA

This study is aimed at providing a critical review of the botany, biological activities and medicinal uses of P. prunelloides. Documented information on botany, biological activities, and medicinal uses of P. prunelloides was collected from several online sources which included BMC, Scopus, SciFinder, Google Scholar, Science Direct, Elsevier, PubMed, and Web of Science. Additional information on the botany, biological activities, and medicinal uses of P. prunelloides was gathered from book chapters, books, journal articles, theses, and scientific publications sourced from the University of Fort Hare Library. The study showed that the leaves and roots of P. prunelloides are used as herbal medicines for bodily pains, burns, cancer, diabetes, fever, gastrointestinal problems, heartburn, heart problems, respiratory problems, retained placenta, rheumatism, sexually transmitted infections, skin infections, snakebite, sores, wounds, toothache, and vomiting. Pharmacological research revealed that P. prunelloides extracts have antibacterial, antimycobacterial, antifungal, antiviral, antidiabetic, anti-inflammatory, analgesic, antioxidant, uterotonic and cytotoxicity activities. Future studies should focus on evaluating the phytochemical, pharmacological, and toxicological activities of P. prunelloides crude extracts as well as chemical compounds isolated from the species.


INTRODUCTION
Pentanisia prunelloides (Klotzsch ex Eckl. and Zeyh.) Walp. is a member of the Rubiaceae family and an important component of the grassland biome in south-central Africa. The fleshy, tuberous root is mainly used as herbal medicine, but sometimes also the leaves. The roots of P. prunelloides are ingredients of a herbal concoction referred to as "isihlambezo" consisting of Agapanthus africanus (L.) Hoffmans (roots),  [1][2][3][4]. Isihlambezo is used to induce or augment labor, is used as a postnatal medication to expel afterbirth, is administered to animals to expel the placenta, and is also used in the treatment of endometritis [3,4]. The roots of P. prunelloides are ingredients of another herbal concoction known as "sejeso" (Ingwe @ brand), made up of Elephantorrhiza elephantina (Burch.) Skeels, Alepidea amatymbica Eckl. and Zeyh., Hypoxis obtusa Burch. ex Ker Gawl., deionized water, and potassium sorbate as a preservative, which is used as a remedy for constipation, heartburn, indigestion, loss of appetite, stomach ailments, and vomiting [5][6][7]. Research by Famewo et al. [8,9] revealed that P. prunelloides is an ingredient of a polyherbal medicine mixed with Centella eriantha (A.Rich.) Drude (rhizome), Hypoxis argentea Harv. ex Baker (corm), Kniphofia drepanophylla Baker (root), Rapanea melanophloeos (L.) Mez (bark), and Strychnos decussata (Pappe) Gilg (bark) which is used as a herbal medicine for tuberculosis.
Due to the popularity of the species as a herbal medicine, the roots of P. prunelloides are sold in informal herbal medicine markets in the Eastern Cape [10,11], KwaZulu-Natal province [12], and Western Cape [11] provinces in South Africa. P. prunelloides is also one of the important medicinal plants in South Africa, included in the book "Medicinal Plants of South Africa," a photographic guide to the most commonly used plant medicines in the country, including their botany, main traditional uses, and active ingredients [13]. According to Arnold et al. [14] and Van Wyk [15,16], the roots and leaves of P. prunelloides have commercial potential as remedies for headache, pain, and wounds and act as a purgative in South Africa. Therefore, P. prunelloides is an integral part of traditional pharmacopoeia in South-Central Africa with potential contribution to primary health care of local communities in the region [17,18]. Therefore, this is the rationale behind the current study, aimed at providing a critical appraisal of the existing ethnomedicinal uses, phytochemistry, and biological activities of P. prunelloides.

DESCRIPTION AND TAXONOMY OF P. PRUNELLOIDES
The genus name Pentanisia is derived from the Greek word "penta" meaning five and "anisos" which means unequal, in reference to the calyx lobes. The specific epithet "prunelloides" means resembling members of the genus Prunella L. (Lamiaceae family) derived from the Latin word "prunus" which means purple [19]. P. prunelloides is divided into two subspecies, namely P. prunelloides subsp. latifolia (Hochst.) Verdc. and P. prunelloides subsp. prunelloides [20,21]. In South Africa, both subspecies have height ranging from 10 cm to 45 cm and have been recorded at an altitude ranging from 10 m to 2200 m above the sea level [21]. However, most ethnobotanical and ethnopharmacological literature do not separate P. prunelloides into specific subspecies, but rather P. prunelloides sensu lato, and this is the approach that has been adopted in the current review. Synonyms associated with P. prunelloides include Diotocarpus prunelloides (Klotzsch) Hochst., P. variabilis Harv. var. intermedia Sond., and P. variabilis Harv. var. latifolia (Hochst.) Sond. [20,21]. The species has been recorded in Lesotho, Malawi, Mozambique, South Africa, Swaziland, Tanzania, and Zambia [20,21]. P. prunelloides is a perennial herb of about 0.6 m in height and 0.6 m wide [13,22]. P. prunelloides is a multi-stemmed herb often trailing in the grass or erect. The leafy, hairy, stout, and spreading branches sprout from a thick and tuberous rootstock [13]. The leaves are without stalks, with waxy margins; are oblong in shape; are borne in pairs; are narrow; and are usually hairless. The tubular blue or lilac flowers are borne in heads on stalks above the leaves on the branch ends. P. prunelloides has Maroyi been recorded in well-drained sandy and loamy soils. P. prunelloides is long lived and dormant in the winter months [13]. The English common names of the species are wild verbena and broad-leaved pentanisia; other vernacular names include sooibrandbossie and wild verbena (Afrikaans), khatoane and setimamollo (Sotho), icikamlilo, icimamlilo, and icishamlilo (Xhosa), icimamlilo, icishamililo-elincane, incishamlilo, and umakuphole (Zulu) [13,19,22,23].

MEDICINAL USES OF P. PRUNELLOIDES
A wide range of medicinal uses of P. prunelloides have been reported in literature (Table 1). Its major uses have been reported in at least two countries and literature records include its treatment of bodily pains, burns, cancer, diabetes, fever, gastrointestinal problems, heartburn, heart problems, respiratory problems, retained placenta, rheumatism, sexually transmitted infections, skin infections, snakebite, sores, wounds, toothache, and vomiting. In South Africa, the roots of P. prunelloides are mixed with those of Jatropha zeyheri Sond. and Warburgia salutaris (Bertol.f.) Chiov. as herbal medicine for blisters, bruises, burns, and cuts [24,25]. The roots of P. prunelloides are mixed with those of E. elephantina as herbal medicine for eczema [7,[24][25][26][27]. According to Bryant [28] and Hutchings et al. [23], the roots of P. prunelloides are mixed with those of Withania somnifera (L.) Dun. as herbal medicine for gangrenous rectitis. Research by Bisi-Johnson et al. [29] and Mpofu et al. [6] revealed that the roots of P. prunelloides are mixed with those of Acokanthera oblongifolia (Hochst.) Codd and E. elephantina as remedy for stomach ailments. The roots of P. prunelloides are mixed with those of Dicoma anomala Sond. [24][25][26]30,31] or are mixed with roots of D. anomala and bulbs of Hypoxis colchicifolia Baker [24,25,27] as remedy for insect and sting bites. According to Masika and Afolayan [32], the leaves of P. prunelloides are mixed with those of Cannabis sativa L. and glycerin as ethnoveterinary medicine for conjunctivitis and retained placenta.

Antibacterial activities
Yff et al. [42] evaluated the antibacterial activities of aqueous, ethanolic, and ethyl acetate extracts of the leaves and roots of P. prunelloides against Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus, using the serial dilution technique with neomycin as the positive control. The extracts exhibited activities with minimum lethal concentration values, ranging from 0.4 mg/ml to 12.5 mg/ml against 0.4 µg/ml to 3.1 µg/ml exhibited by the control [42]. Jäger [86] evaluated the antibacterial activities of aqueous ethyl acetate root extracts of P. prunelloides against S. aureus and B. subtilis using the microtiter plate assay with neomycin as positive control. The extract exhibited activities with minimum inhibitory concentration (MIC) value of >1.0 mg/ml and >2.0 mg/ml against 1.6 μg/ml and 3.1 µg/ml exhibited by the control [86]. Mabona [25] and Mabona et al. [30] evaluated the antibacterial activities of aqueous and dichlomethane: methanol (1:1) root and root bark extracts of P. prunelloides using the microtiter plate assay against dermatologically relevant pathogens such as Brevibacillus agri, Propionibacterium acnes, Pseudomonas aeruginosa, S. aureus, and S. epidermidis with ciprofloxacin as a positive control. The extracts exhibited activities with MIC values ranging from 1.0 mg/ml to >16.00 mg/ml. Mabona et al. [30] also evaluated the interactive antibacterial activities of P. prunelloides root mixed with E. elephantine rhizome; P. prunelloides root and root bark mixed with D. anomala tuber against P. aeruginosa, S. aureus, and S. epidermidis. These combinations produced synergistic effects with MIC values from 0.5 mg/ml to >16.00 mg/ml, with the sum of the ∑fractional inhibitory concentration (∑FIC) values ranging from 0.3 to 4.0 [25,30]. Madikizela et al. [60] and Madikizela [61] evaluated the antibacterial activities of dichloromethane, petroleum ether, ethanol, and water extracts of leaves and roots of P. prunelloides against K. pneumoniae, S. aureus, and Mycobacterium aurum using the microdilution assay with neomycin and streptomycin as positive controls. The extracts exhibited activities with MIC values ranging from 0.2 mg/ml to 12.5 mg/ml, with the positive controls exhibiting MIC values ranging from 0.05 mg/ml to 0.2 mg/ml [60,61]. Mpofu et al. [6] evaluated the antibacterial activities of the methanol and aqueous root extracts of P. prunelloides using the microtiter assay against Bacillus cereus, Enterococcus faecalis, and E. coli with ciprofloxacin as a positive control. The extracts exhibited activities with MIC values ranging from 0.4 mg/ mL to 16.0 mg/mL. Mpofu et al. [6] also evaluated the antibacterial activities of P. prunelloides combined with E. elephantina in 1:1 ratio which exhibited activities ranging from 0.2 mg/mL to 4.0 mg/mL, displaying synergistic interactions with sum of the values ranging from 0.2 to 1.0 against B. cereus, E. faecalis, and E. coli. Mpofu et al. [6] also evaluated the antibacterial activities of (-)-epicatechin and palmitic acid isolated from P. prunelloides roots using the microtiter plate dilution technique against B. cereus, E. faecalis, and E. coli with ciprofloxacin as a positive control. The compounds exhibited activities with MIC values ranging from 0.1 mg/mL to 0.6 mg/mL, whereas combination of the two compounds exhibited activities with MIC values ranging from 0.2 mg/mL to 4.0 mg/mL; synergistic interactions were noted against E. coli and E. faecalis with ΣFIC values of 0.1 and 0.50, respectively [6]. Mugomeri et al. [63] used the checkerboard microdilution technique to determine the efficacy of mixing (-)-epicatechin and palmitic acid or any of these two compounds with P. prunelloides against B. cereus, S. aureus, E. coli, K. pneumonia, and E. faecalis. The results demonstrated that the combinations resulted in either additive or synergistic effects, but no antagonistic interactions were observed [65]. Muleya [87] and Muleya et al. [88] evaluated the antibacterial activities of crude, hexane, dichloromethane, ethyl acetate, acetone, and methanol root extracts of P. prunelloides against S. aureus, E. coli, E. faecalis, and P. aeruginosa using serial dilution assay. The extracts exhibited activities with MIC values ranging from 150.0 µg/ml to 650.0 μg/ml [87,88]. Xaba [31] and Xaba and Buwa [89] evaluated the antibacterial activities of methanol, ethanol, acetone, and aqueous root extracts of P. prunelloides against P. aeruginosa, Bacillus pumilus, S. aureus, E. coli, and K. pneumonia using microplate dilution assay. The extracts exhibited activities with MIC values ranging between 0.1 mg/ml and 6.3 mg/ml [31,89].

Antifungal activities
Mabona [25] and Mabona et al. [30] evaluated the antifungal activities of aqueous and dichloromethane: methanol (1:1) root and root bark extracts  [30] also evaluated the interactive antifungal activities of P. prunelloides root mixed with E. elephantina rhizome; P. prunelloides root and root bark mixed with D. anomala tuber against C. albicans. These combinations produced synergistic effects with MIC values of 2.0 mg/ml to 16.00 mg/ml and ∑FIC values ranging from 0.3 to 3.0 [25,30]. Muleya [87] and Muleya et al. [88] evaluated the antifungal activities of acetone root extracts of P. prunelloides against C. albicans and Aspergillus fumigatus using serial dilution assay. The extracts exhibited activities with MIC value of 625.0 μg/ml [87,88]. Xaba [31] and Xaba and Buwa [89] evaluated the antifungal activities of methanol, ethanol, acetone, and aqueous root extracts of P. prunelloides against C. albicans and Trichophyton mucoides using microplate dilution assay. The extracts exhibited activities with an MIC value of 0.5 mg/ml [31,89].

Antiviral activities
Yff et al. [42] evaluated the antiviral activities of aqueous extracts of leaves and roots of P. prunelloides using antiviral assays aimed at assessing replication or inhibition of 1000 TCID 50 influenza A as a percentage reduction in the number of fluorescent foci on the infected VK cell cultures. The extracts inhibited viral replication of the influenza A virus [42].

Antidiabetic activities
Makhudu [84] evaluated the antidiabetic activities of the water, ethanol, aqueous-ethanol, and hexane root extracts of P. prunelloides and tormentic acid isolated from the species against the activities of α-amylase, α-glucosidase, sucrose, and maltase with acarbose as a positive control. The extracts exhibited activities with halfmaximal inhibitory concentration (IC 50 ) values ranging from 0.5 µg/mL to 90.5 µg/mL, while the positive control exhibited IC 50 values of 9.9 µg/mL to 129.4 µg/mL. The tormentic acid inhibited α-amylase and α-glucosidase at 70.5 µg/mL and 28.2 µg/mL, respectively [84].

Anti-inflammatory activities
Lindsey et al. [92] evaluated the aqueous and ethanol leaf and root extracts of P. prunelloides for prostaglandin synthesis inhibitors using the cyclooxygenase inhibitory bioassay with indomethacin as the positive control. The aqueous and ethanol leaf extracts inhibited cyclooxygenase at 71%-87%, which was higher than 67% inhibition exhibited by the standard, indomethacin [92]. Yff et al. [42] evaluated the anti-inflammatory activities of aqueous, ethanolic, and ethyl acetate extracts of leaves and roots of P. prunelloides using the cyclooxygenase-1 assay with indomethacin (20 µM) as a positive control. The extracts exhibited activities with percentage inhibition of cyclooxygenase ranging from 65% to 87%, which was comparable to 83% exhibited by the control [42]. Frum and Viljoen [43] and Lehasa et al [91] evaluated the anti-inflammatory activities of aqueous and methanol root extracts of P. prunelloides through the assessment of 5-lipoxygenase inhibitory activities using a threefold step-wise dilution method with dimethyl sulfoxide and Tween ® 20 as negative controls and nordihydroguaiaretic acid as a positive control. The methanol extract exhibited 5-lipoxygenase inhibitory activities with IC 50 value of 32.7 ppm [43]. Madikizela [61] and Madikizela et al. [90] evaluated the anti-inflammatory activities of dichloromethane, petroleum ether, ethanol, water, leaf, root, and whole plant part extracts of P. prunelloides using the cyclooxygenase-2 (COX-2) inhibition assay with indomethacin as a positive control. The highest COX-2 inhibition was exhibited by petroleum ether against the root extract at 86.9% [61,90]. Muleya [87] and Muleya et al. [88] evaluated the anti-inflammatory activities of acetone root extracts of P. prunelloides against 15-soybean lipoxygenase enzyme. The lipoxygenase inhibitory activity of 79% indicates high anti-inflammatory activity [87,88].
Mathews et al. [83] evaluated the anti-inflammatory activities of leaf and root aqueous extracts of P. prunelloides on egg albumin-induced rat paw edema model, with aspirin used as a standard drug. The extracts exhibited dose-dependent anti-inflammatory effects [83]. Xaba [31] evaluated the anti-inflammatory activities of aqueous, acetone, ethanol, and methanol root extracts of P. prunelloides using the 5-lipoxygenase enzyme (Cayman) assay with nordihydroguaiaretic acid as a positive control. The extracts exhibited activities with IC 50 values ranging from 0.2 µg/ml and 0.4 µg/ml, which was comparable to IC 50 value of 0.6 µg/ ml exhibited by the control [31].

Uterotonic activities
Kaido et al. [2] investigated the uterotonic activities of the crude decoction of P. prunelloides on the isolated rat uterus and ileum preparation. The aqueous extract of P. prunelloides initiated contractions in the isolated rat uterus, showed direct smooth muscle activity on the uterus and ileum preparations, and potentiated the initial response of the uterus to oxytocin [2]. Lindsey et al. [92] evaluated the uterinerelaxing activities of ethanol leaf and root extracts of P. prunelloides using in vitro uterine bioassay. The extracts caused mild contraction of the relaxed uterine muscles [92].

Cytotoxicity activities
Mpofu et al. [6] and Mpofu [62] evaluated the cytotoxic activities of the aqueous and methanol root extracts of P. prunelloides using the brine shrimp lethality test. The aqueous and methanol extracts exhibited moderate cytotoxicity with median lethal dose values of 3.2 and 5.6 ppm, respectively [6,62].

CONCLUSION
P. prunelloides is a well-known plant species in South-Central Africa in traditional and folk medicine which is an important part of indigenous Maroyi culture in the region. In many cases, the roots and, sometimes, the leaves are used to manage and treat several human diseases. Detailed phytochemical evaluations are lacking although alkaloids, anthocyanidins, anthraquinones, cardiac glycosides, flavonoids, glucose, saponins, steroids, sucrose, tannins, terpenoids, alanine, allo-isoleucine, α-aminobutyric acid, arabinose, asparagine, aspartic acid, diosgenin, (-)-epicatechin, epicatechin gallate, epigallocatechin gallate, glucuronic acid, hexoses, kaempferol, oleanolic acid, palmitic acid, quercetin, rhamnose, serine, tormentic acid, and valine have been identified from the species. Studies focusing on the biological activities of P. prunelloides crude extracts have been conducted in vitro.
Not much data are available on the biological activities of compounds isolated from the species and toxicity of P. prunelloides crude extracts and chemical ingredients isolated from the species. Therefore, there is a need for further studies focusing on the phytochemistry, pharmacological, toxicological, and in vivo studies involving the crude extracts and chemical ingredients isolated from the species.

ACKNOWLEDGMENTS
I would like to express my gratitude to the National Research Foundation, South Africa, and Govan Mbeki Research and Development Centre, University of Fort Hare, for financial support to conduct this study.

AUTHORS' CONTRIBUTIONS
The author declares that this work was done by the author named in this article.