Evaluation of Ethnomedicine and Ethnobotany ofMaerua triphylla A. Rich. (Capparidaceae)

Maerua triphylla A. Rich. is a shrub or small tree collected from the wild for its edible leaves and also used as traditional medicine. This study is aimed at evaluating the ethnomedicinal and ethnobotanical uses of M. triphylla. Results of the current study are based on data derived from several online databases such as Scopus, Google Scholar, PubMed and Science Direct, and pre-electronic sources such as scienti ic publications, books, dissertations, book chapters and journal articles. This study revealed that the fruit, leaf, root, stem bark and twig infusion and/or decoction of M. triphylla are mainly used as ethnoveterinary medicine, aphrodisiac and antidote for poisoning, and traditional medicine for rheumatism, boils, cancer, respiratory problems, snakebite, headache,migraine and gastro-intestinal problems. Phytochemical compounds identi ied from dried aerial parts and branches of M. triphylla include betaines and quaternary ammonium compounds such as 3hydroxyprolinebetaine, glycine betaine, proline betaine and 3-hydroxy-1,1dimethyl pyridinium. Preliminary ethnopharmacological research revealed thatM. triphylla leaf extracts have acaricidal and cytotoxicity activities. Documentation of the medicinal uses, phytochemistry and pharmacological properties of M. triphylla is important as this information provides baseline data required for future research focusing on ethnopharmacological properties of the species. Maerua triphylla should be subjected to detailed phytochemical, pharmacological and toxicological evaluations aimed at correlating its medicinal uses with its phytochemistry and pharmacological properties”


INTRODUCTION
Maerua triphylla A. Rich. is a shrub or small tree belonging to the Capparaceae or caper family. The Capparaceae family is a tropical and subtropical taxon of trees, shrubs, herbs and lianas consisting of approximately 417 species (Kers et al., 2003;Iltis et al., 2011) The genus Maerua Forssk has been recorded in tropical and southern Africa, and tropical Asia with about 60 species recorded from the African continent (Elfers et al., 1964). The genus name "Maerua" means "drooping" about the drooping foliage (Venter and Venter, 2015). The speci ic epithet "triphylla" is a Greek word meaning "three lea lets" about the trifoliate leaves that characterize the species.
Maerua triphylla is variable and four varieties, namely var. calophylla (Gilg) DeWolf, var. Johannis (Volkens & Gilg) DeWolf, var. pubescens (Klotzsch) DeWolf and var. triphylla have been described (DeWolf, 1962). However, in Kenya, where all four varieties have been recorded, it was found to be impossible to eliminate the varieties as the morphological characteristics appeared to be continuous (Mollel, 2013). The English common names of M. triphylla are "small bead-bean" and "maerua" (Dharani, 2019 Gilg, M. trachycarpaGilg, M. trichocarpa Gilg & Gilg-Ben. and M. variifolia Gilg & Gilg-Ben (Wild, 1960;Elfers et al., 1964). Maerua triphylla is an evergreen, erect or scandent tree or shrub, growing to a height of nine meters (Palgrave, 2002) The branches of M. triphylla are dense, long, pendulous, young branches brown, glabrous with several lenticels and forming a round crown. The leaves are alternate, simple, trifoliate, with entire margins, dull grey-green, narrowly oval with a rounded apex. The lowers are small, regular, bisexual, cream to white, borne singly in the upper leaf axils. The fruit is a cylindrical capsule and constricted between the seeds, bluish-green at irst, turning creamy-brown when ripe. The seeds are irregularly kidney-shaped, pale brown and obscurely warted. Maerua triphylla has have been recorded in evergreen or deciduous bush land, wooded grassland, dry woodland, termite mounds, thickets and margins of the drier forests, along rivers and lakes. Maerua triphylla has have been recorded in the Democratic Republic of Congo, Ethiopia, Djibouti, Tanzania, Kenya, Uganda, Somalia, South Sudan, Sudan, Malawi, Mozambique, Zambia, Zimbabwe, Madagascar and Seychelles an altitude ranging from sea level to 2300 m above sea level (Elfers et al., 1964;Palgrave, 2002).
The leaves of M. triphylla are eaten as leafy vegetables in Ethiopia and Tanzania (Luoga et al., 2000;Lulekal et al., 2011) and also consumed as famine food (Mollel, 2013). In Kenya and Tanzania, during periods of famine, the roots of M. triphylla are boiled for a long time to remove toxic compounds and prepared as porridge (Hamilton and Hamilton, 2006;Dharani, 2019). The species is also important for bee forage (Mollel, 2013). Wild and domesticated animals browse the leaves and shoots of M. triphylla in Kenya, Ethiopia and Uganda (Gemedo-Dalle et al., 2006;Mbuvi et al., 2019). In East Africa, M. triphyllais planted in rocky sites, and other degraded landscapes as a management strategy for soil reclamation, and the species is often spared when clearing land for agricultural purposes (Mollel, 2013). Maerua triphylla is one of the important medicinal plants in tropical Africa, and the species is included in the book "Plant resources of tropical Africa 11(2): Medicinal plants 2", a photographic guide to the most commonly used medicinal plants in tropical Africa (Mollel, 2013). Therefore, M. triphylla is a valuable plant species with potential for improving food and nutritional security and primary healthcare of local communities in tropical Africa. Thus, this review aims to provide an integrated and detailed appraisal of the existing knowledge on the ethnomedicinal uses and ethnobotany of M. triphylla.

MATERIALS AND METHODS
Results of the current study are based on a literature search on the ethnomedicinal uses and ethnobotany of M. triphylla using information derived from several internet databases. The databases included Scopus, Google Scholar, PubMed and Science Direct. Other sources of information used included preelectronic sources such as journal articles, theses, books, book chapters and other scienti ic articles obtained from the university library.

Medicinal uses of Maerua triphylla
The fruit, leaf, root, stem bark and twig infusion and decoction of M. triphylla are mainly used as ethnoveterinary medicine, aphrodisiac and antidote for poisoning, and traditional medicine for rheumatism, cancer, respiratory problems, snakebite, headache and gastrointestinal problems (Table 1 ; Figure 1). In Tanzania, the leaves of M. triphylla are mixed with those of Boscia salicifolia Oliv and taken orally as an antidote for poisoning and traditional medicine for tuberculosis (Hedberg et al., 1982;Maroyi, 2019). In Kenya, the roots of M. triphylla are mixed with those of Uvaria acuminata Oliv and taken orally as traditional medicine for breast cancer, dizziness and hallucinations (Waswala-Olewe et al., 2014).  (Hedberg et al., 1982;Maroyi, 2019) Aphrodisiac Leaf, root and stem bark infusion and decoction are taken orally Kenya and Tanzania (Hedberg et al., 1982;Kimondo et al., 2015) Backache Leaf infusion and decoction are taken orally Tanzania (Matthews, 1993) Boils Leaf ash applied topically Djibouti and Kenya (Ichikawa, 1987;Hassan-Abdallah et al., 2013) Burns Leaf decoction applied topically Kenya (Fratkin, 1996) Cancer ( (Hedberg et al., 1982) Wounds Leaf, root and stem bark decoction applied topically Kenya (Fratkin, 1996;Kimondo et al., 2015) Ethnoveterinary medicine (Babesiosis, red water disease, galactagogue and ticks) Leaf infusion and decoction are taken orally or leaves mixed with those of Parvonia spp., Phytolacca dodecandra L'Hér. and Tagetes minuta L. taken orally Ethiopia and Uganda (Katunguka-Rwakishaya et al., 2004;Zorloni, 2008) Similarly, the roots of M. triphylla are mixed with those of Capparis cartilaginea Decne. As traditional medicine for headache, and the roots of M. triphylla are mixed with those of U. acuminata and bark of Boscia angustifolia A. Rich. and used against snakebites (Waswala-Olewe et al., 2014). In Ethiopia, leaves of M. triphylla are mixed with those of Parvonia spp., Phytolacca dodecandra L'Hér. and Tagetes minuta L. and used as ethnoveterinary medicine for babesiosis or red water disease (Katunguka-Rwakishaya et al., 2004).

Phytochemical and pharmacological properties of Maerua triphylla
The ethnobotanical data about M. triphylla is related to three primary use categories which are centered around herbal medicine, fodder and a source of food, especially during dif icult times. However, there is very little information available concerning the phytochemistry and pharmacological properties of the crude extracts or compounds isolated from the species. Little work has been done to characterize the nutritional attributes of M. triphylla, but a report on its leaves showed high amounts of proteins averaging 21.4% (Lehouérou, 1980;Mollel, 2013). There is need for nutritional evaluation of both the leaves and roots of the species as M. triphylla is widely used as wild food, both as supplementary and famine food (Luoga et al., 2000;Lulekal et al., 2011). There is also need to evaluate the toxicological properties of the species as uncooked roots are perceived as toxic, and boiling and reboiling them several times is suggested to render them non-toxic and edible (Hamilton and Hamilton, 2006;Tairo, 2011). (McLean et al., 1996 identi ied the betaines and quaternary ammonium compounds such as 3-hydroxyprolinebetaine, glycine betaine, proline betaine and 3-hydroxy-1,1-dimethyl pyrrolidinium from dried aerial parts and branches of M. triphylla. (Loontjens, 2013) argued that quaternary ammonium compounds are potent biocides widely used in medical applications, cosmetics, disinfectants, surfactants and solvents. Some of these phytochemical compounds may be responsible for the biological activities of the species. (Zorloni, 2008) evaluated the acaricidal activities of acetone and hexane extracts of M. triphylla leaves against adult Rhipicephalus pulchellus ticks. The extracts exhibited good repellent properties against the ticks at 10.0% concentration. These indings support the use of leaf infusion and decoction against ticks in Ethiopia (Zorloni, 2008). (Matata et al., 2018) evaluated the cytotoxicity activities of methanol: dichloromethane (1:1) extracts of M. triphylla leaves using the brine shrimp toxicity assay with Catharanthus roseus (L.) G. Don. Anticancer compounds characterized it as a positive control. The extract exhibited moderate activities with median lethal concentration (LC 50 )value of 57.5µg/ml in comparison to LC 50 value of 6.7 µg/ml exhibited by the positive control (Matata et al., 2018). Therefore, the brine shrimp assay results corroborate ethnomedicinal applications of the roots and stem bark of the species against breast cancer and leukaemia in Tanzania (Augustino and Gillah, 2005;Matata et al., 2018).

CONCLUSIONS
Maerua triphylla is known to be poisonous, and there is a need for detailed clinical and toxicological evaluations of crude extracts and compounds isolated from the species. Therefore, the widespread use of M. triphylla as food plant and source of traditional medicines throughout its distributional range suggest that the species is not taken at toxic dosages. But the use of M. triphylla as food and for the treatment of human diseases and ailments should be treated with caution and rigorous toxicological and clinical studies of the bark, fruits, leaves, roots and tubers, and compounds isolated from the species are necessary.

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