ZANTEDESCHIA AETHIOPICA (L.) SPRENG.: A REVIEW OF ITS MEDICINAL USES, PHYTOCHEMISTRY, AND BIOLOGICAL ACTIVITIES

Zantedeschia aethiopica is an evergreen monocotyledonous herb widely used as herbal medicine and ornamental plant. The current study is aimed at reviewing the medicinal uses, phytochemistry, and biological activities of Z. aethiopica. Information on biological activities, medicinal uses, and phytochemistry of Z. aethiopica was gathered from several internet sources which included Scopus, Google Scholar, Elsevier, Science Direct, Web of Science, PubMed, SciFinder, and BMC. Additional information on these aspects was sourced from pre-electronic sources such as journal articles, scientific reports, theses, books, and book chapters obtained from the University Library. The current study revealed that Z. aethiopica is mainly used as herbal medicine for boils, burns, gout, inflammation, insect bites, rheumatism, sores, and wounds. Phytochemical and pharmacological studies showed that Z. aethiopica extracts and compounds isolated from the species have antibacterial, antifungal, antioxidant, antihistaminic, antialgal, antithrombotic, and anticoagulant activities. This research showed that Z. aethiopica is an integral part of the traditional pharmacopeia in several countries where the species is indigenous or naturalized, but there is the lack of alignment between the known medicinal applications, phytochemistry, and biological activities of the species. Therefore, future research should focus on evaluating the chemical and pharmacological properties of Z. aethiopica extracts and compounds associated with the species.


INTRODUCTION
Zantedeschia aethiopica (L.) Spreng. is an evergreen herb which is a member of a monocotyledonous flowering plants Araceae family also known as arum lily family. Z. aethiopica is an important food, medicinal and ornamental plant in Africa, Asia, Australia, Europe, and the United States of America, and recently playing an important role in cleaning up contaminated soils and water [1][2][3][4][5][6]. Research by Halligan et al. [7] and Wei et al. [8] showed that Z. aethiopica is sold worldwide as an ornamental plant and the species is cultivated commercially as an ornamental flower [9][10][11][12] with the foliage and flowers employed principally for coronas and other funeral decorations on altars and shrines and as cut flowers. In South Africa, Z. aethiopica is one of the valuable medicinal plant species in the country and the species is included in the book "medicinal plants of South Africa," a photographic guide to the most commonly used herbal medicines in the country, including its botany, major medicinal applications active phytochemical compounds [13]. Similarly, research by Reinsten et al. [12] showed that Z. aethiopica has commercial potential for the cut flower trade as potted flowers and foliages in South Africa. The tuberous rootstock of Z. aethiopica is said to have been a food source in early days in South Africa after extensive boiling to counteract the burning effect of the raphide crystals [14,15]. The leaves and stems of Z. aethiopica are cooked as potherbs and leafy vegetables in Lesotho, Zimbabwe, the Eastern Cape, Free State, and KwaZulu-Natal Provinces in South Africa [14][15][16][17][18][19][20][21][22][23][24][25][26]. However, the leaves of Z. aethiopica are among the top 10 culprits of plant species responsible for about 6.5% of all poisoning cases (about 500 cases and inquiries per year) in the Johannesburg municipal area in South Africa [27]. Although Z. aethiopica is not indigenous to New Zealand, the species is the second most common poisonous plant in the country [28]. Research by Botha and Penrith [29], Wink and Van Wyk [30], and Ndhlala et al. [31] showed that the cardiac glycosides which have been identified from the species and known to induce paralysis on the central nervous system are probably responsible for the toxic properties of the species. However, Van Wyk et al. [27] argued that Z. aethiopica is not toxic, but the oxalate crystals associated with the species may cause distress if fresh leaves are eaten. Similarly, Van Wyk et al. [13] argued that Z. aethiopica should not be eaten fresh as the needle-shaped calcium oxalate crystals cause mechanical irritation of the mucous membranes, causing swelling of the tongue and throat, salivation, nausea, vomiting, and diarrhea. However, Z. aethiopica is a valuable medicinal plant, as its rhizomes and roots are sold as herbal medicines in the Limpopo Province in South Africa [32,33] and Brazil [34,35]. It is within this context that the current study was undertaken aimed at providing a comprehensive review of the medicinal value, phytochemistry and biological activities of the compounds isolated from the species, including Z. aethiopica crude extracts.

BOTANICAL DESCRIPTION OF Z. AETHIOPICA
Z. aethiopica is a perennial, robust, evergreen or deciduous, erect and clump-forming herbaceous plant with a thick rhizome and white fleshy roots. Z. aethiopica grows up to 150 cm in height with large, fleshy leaves developing from the tuberous rhizome [36][37][38][39]. The leaves are dark glossy green in color, lack a persistent basal meristem, are large, leathery and hairless, ovate in shape with parallel-pinnate veins, characterized by a thick and spongy leaf stalk. The minute yellow or cream-colored flowers are borne in a dense group on a finger-like column (so-called spadix), surrounded by a large, white, leaf-like structure (the spathe) [13]. A dense mass of small, fleshy, soft, berrylike yellow fruits develops at the base of the spadix. Z. aethiopica is native to Lesotho, South Africa, and Swaziland [14,17,36,37,[40][41][42]. In Southern Africa, Z. aethiopica has been recorded in sandy or rocky places, along the coast, mountain grasslands, usually seasonally damp depressions and permanent springs at an altitude ranging from 20 m to 2250 m above sea level [38,39,41]. Z. aethiopica is also naturalized in Australia, Brazil, Hawaii, India, Italy, Kenya, Malawi, New Zealand, Philippines, Portugal, Réunion, South America, Spain, Tanzania, Tunisia, the United Kingdom, and Zambia [42][43][44][45][46][47][48][49][50].

MEDICINAL USES OF Z. AETHIOPICA
The leaves, rhizomes, roots, stems, and the whole plant parts of Z. aethiopica are used as herbal medicines against 33 human diseases in tropical Africa, Asia, and North America (Table 1). Z. aethiopica is mainly used as herbal medicine for boils, burns, gout, inflammation, insect bites, rheumatism, sores, and wounds ( Fig. 1). Other medicinal applications recorded in at least two literature sources include asthma, colds, flu, headache, heartburn, infections, infertility, respiratory problems, sore throat, and as a protective charm (Table 1). Such wide usage of Z. aethiopica as herbal medicine implies that the species is a valuable source of therapeutic agents required for plant-derived natural products or their derivatives.

CHEMICAL AND PHYTOCHEMISTRY OF Z. AETHIOPICA
Carneiro et al. [89] and Pelo [90] quantified mineral elements in flower stalks, leaves, rhizomes, and roots of Z. aethiopica including heavy metals such as cadmium, copper, chromium, iron, lead, manganese, and mercury ( Table 2). The concentrations of the heavy metals in Z. aethiopica are below the permissible FAO or the WHO limits set by Codex Alimentarius Commission [91], and therefore, the use of the species as food or its extracts as herbal medicines may not result in heavy metal toxicity. Medicinal plants growing in different geographical areas usually accumulate different levels of heavy metals [92,93]. Phytochemical compounds that have been identified from flowers, fruits, leaves, and regreened sphates, and stems of Z. aethiopica include alkaloids, anthraquinones, cardiac glycosides, flavonoids, glucose, saponins, soluble starch, steroids, sucrose, tannins, and terpenoids [90,[94][95][96]. Other phytochemical compounds that have been   Table 3).

Antibacterial activities
Nielsen et al. [63] [64,65]. Motlhatlego [54] evaluated the antifungal activities of aqueous, dichloromethane, 80% ethanol and petroleum ether leaf, rhizome, root, and stem extracts of Z. aethiopica against C. albicans using microdilution technique with   Maroyi amphotericin B as a positive control. The extracts exhibited activities with MIC and minimum fungicidal concentration (MFC) values ranging from 1.6 mg/ml to >12.5 mg/ml which was comparable to MIC and MFC values of 0.008 mg/ml and 0.01 mg/ml, respectively, which were exhibited by the controls [54].

Antithrombotic and anticoagulant activities
Kee et al. [104] evaluated antithrombotic and/or anticoagulant activities of methanol and aqueous leaf extracts of Z. aethiopica using the thrombin and clotting time (thrombin induced and CaCl 2 induced) assays. The extract displayed anticoagulant activities with half maximal inhibitory concentration (IC 50 ) value of 3.1 mg/ml [104].

Antioxidant activities
Li et al. [105] evaluated the antioxidant activities of the flower extracts of Z. aethiopica using the ferric-reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays. The extracts exhibited FRAP value of 22.1 ± 0.6 µmol Fe(II)/g wet weight while the TEAC value was 9.2±0.4 µmol Trolox/g wet weight and the total phenolic content was 3.1±0.01 mg GAE/g wet weight.
Li et al. [105] also evaluated the insoluble-bound components of the residue using the NaOH hydrolysis and FRAP value was 0.7±0.08 µmol Fe(II)/g wet weight, TEAC (0.3±0.04 µmol Trolox/g wet weight), and the total phenolic content was 0.3±0.01 mg GAE/g wet weight.

Antihistaminic activities
Motlhatlego [54] evaluated the antihistaminic activities of the ethanolic leaf, rhizome, root, and stem extracts of Z. aethiopica using antihistamine assay. The leaf extracts exhibited histamine receptor binding of 88% at both concentrations of 400 µg/ml and 800 µg/ml [54].

CONCLUSION
Z. aethiopica is a well-known medicinal plant species in Southern Africa where the species is indigenous. The species has been introduced in several countries and is now regarded an important component of indigenous pharmacopoeia in Brazil, India, Malawi, Mexico, and Tanzania where the species is naturalized. The historical traditional usage of Z. aethiopica as herbal medicine in Southern Africa and other regions where the species is naturalized calls for detailed phytochemical and pharmacological studies aimed at correlating its documented ethnomedicinal uses with the phytochemical and pharmacological properties of the species. There is a need for clinical and toxicological evaluations since Z. aethiopica contains potentially toxic compounds. Therefore, future research should focus on identification of toxic compounds, the possible side effects caused by taking Z. aethiopica as herbal medicine, and mechanisms of how potential toxic components of the species can be managed when the species is used as herbal medicine.

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.

CONFLICTS OF INTEREST
The author declares that he has no conflicts of interest.