Herbal Drugs from Sudan: Traditional Uses and Phytoconstituents.

Sudan folklore medicine is characterized by a unique combination of Islamic, Arabic, and African cultures. In poor communities, traditional medicine has remained as the most reasonable source of treatment of several diseases and microbial infections. Although the traditional medicine is accepted in Sudan, to date there is no updated review available, which focuses on most effective and frequently used Sudanese medicinal plants. Thus, this review aims to summarize the published information on the ethnobotanical uses of medicinal plants from Sudan, preparation methods, phytochemistry, and ethnopharmacology. The collected data demonstrate that Sudanese medicinal plants have been reported to possess a wide range of traditional medicinal uses including different microbial infections, gastrointestinal disorders, malaria, diabetes, rheumatic pain, respiratory system disorders, jaundice, urinary system inflammations, wounds, cancer, and different microbial infections. In most cases, the pharmacological studies were in agreement with traditional uses. Moreover, several bioactive compounds such as flavonoids, saponins, alkaloids, steroids, terpenes, tannins, fatty acids, and essential oils have been identified as active constituents. Although this review demonstrates the importance of ethnomedicine medicines in the treatment of several diseases in Sudan, further researches to validate the therapeutic uses and safety of these plants through phytochemical screening, different biological activity assays, and toxicological studies are still needed.

INTRODUCTION

Traditional medicine has been used for the treatment of human illnesses since long time and is mainly based on components derived from natural products, from herbs, plants, and animals. Medicinal natural products are very frequently used in Sudan and also are widely consumed in Africa and all over the world. About 80% of the populations in African countries depend on traditional medicine for their primary health care.[1] In Sudan, 90% of Sudan's population depends mainly on traditional medicine since admission to hospitals and obtaining modern synthetic drugs are limited and a high percentage of the population is nomads.[23] Sustainability of the use of medicinal plants is an important concern. The demand for medicinal plants is increasing in Africa as the population grows and pressure on medicinal plant resources will become greater than ever. Interest in plant-derived medicines has also increased in the developed countries among the pharmaceutical companies.[4] In contrast, due to their minor side effects, the medicinal plants are widely used to treat many human diseases.[5] The increasing cost of health care and the failure of allopathic medicine to treat some diseases have also participated to the increasing consumption of traditional medicine to fight disease. Until now, there is no pharmacopoeia or formal training for the traditional medical healers in Sudan, and their knowledge is completely based on acquired folklore and local traditions.

Medicinal plants with a long history of safe and efficient use are likely to have a pharmaceutical outcome.[6] However, almost all of the medicinal herbal products are unlicensed and are not required to demonstrate efficacy, safety, or quality. Unknown consequences of some of medicinal plants have been detected. Examples of toxic reactions, allergic reactions, drug interactions, drug contamination, and mistaken plant identities are provided.[7]

This review describes the traditional uses of 48 medicinal plants from Sudan. These plants are distributed into 26 families. The most common families are Fabaceae (12 species) followed by Combretaceae (4 species), Capparidaceae and Capparaceae (3 species each), Meliaceae, Asclepiadaceae, Anacardiaceae, and Malvaceae (2 species each), and other families are represented with one species each [Table 1]. Different plant parts including leaf, stem, root, fruit, seed and bark, aerial part, and whole plant are used in the preparation of medicines. There is a distinct preference for leaf (25%), fruit (23%), and stem (17%) materials [Figure 1]. Drugs were prepared mostly through decoction (19 species) and maceration (13 species). However, other techniques such as infusion (8 species), poultice and smoke (7 species each), powder and paste (6 species each), directly (2 species), and mucilaginous and dessert (1 species each) are also employed [Figure 2]. Prepared remedies are administered or prescribed in several ways including orally, nasally, or anally. The majority of the species are extensively used in traditional medicine against infections, inflammation, diabetes, bleeding, malaria, diarrhea, and digestive disorders. A summary of the most important Sudanese medicinal plants, their botanical families, local names, and traditional usage is presented in Table 1.

Table 1

Sudanese medicinal plants, their local names, and traditional usage

Figure 1

Plant parts used to prepare traditional medicines

Figure 2

Preparation methods used to practice traditional remedies

The Convention on Biological Diversity (CBD) was opened for signature in 1992 and entered into force in December 1993. It was signed by Sudan in June 1992 and ratified in October 1995, addresses at global level the entire spectrum of biological diversity, the sustainable use thereof and the fair and equitable sharing of the benefits accruing from that use.[71] All plants mentioned in this study are native to Sudan. In this review, we have considered the medicinal plants from the whole Sudan as one single country; however, in July 2011, Sudan was split into two countries (Sudan and South Sudan). The main question now: How will the medicinal plants and forests of the previous United Sudan be divided between the two new countries and which of the two new countries will benefit from legal protection as laid out by CBD?

OVERLAP BETWEEN FOOD AND MEDICINE IN SUDAN

Overlap between food and medicine is a common phenomenon in Sudan. Many plant substances are used as both foods and medicines. For example, the plants Capsicum frutescens, Ziziphus spina-christi, Cymbopogon proximus, Grewia tenax, Hyphaene thebaica, Hibiscus sabdariffa, Trigonella foenum-graecum, Tamarindus indica, and Sesamum indicum are not only known herbal medicines but also foods, drink, and/or flavorings.[891011234252535559606162637273] Moreover, in Sudan and many other countries, foods containing biologically active natural constituents are eaten regularly. For instance, luteolin is a known biologically active flavonoid found in celery, green pepper, thyme, chamomile tea, perilla, carrots, peppermint, olive oil, rosemary, navel oranges, oregano, and other foods.[7475]

PHYTOCHEMISTRY AND PHARMACOLOGICAL PROPERTIES

The traditional medicinal applications of Sudanese plants have encouraged many pharmacological investigations. Several extracts and purified compounds have been assessed for their biological activities, especially antibacterial, antioxidant, antimalarial, antifungal, anti-inflammatory, anticancer, and antidiabetic activities [Figure 3]. There appears to be an interest in developing novel drugs for many diseases from these plants due to their different classes and high contents of phytoconstituents based on natural products as lead structures. The active components in herbal medicines are directly associated with their ability to treat or prevent ailments. Phenolics, alkaloids, tannins, flavonoids, saponins, and steroids are the most bioactive compounds identified in these plants. Table 2 lists some the available pharmacological studies, bioactive constituents, and assays based on folk knowledge of the most active and frequently used Sudanese medicinal plants.

Figure 3

Major pharmacological studies and plant species reported

Table 2

Main phytochemistry constituents, bioactivity, and pharmacological studies based on folk knowledge of the most active Sudanese medicinal plants

ANTIMICROBIAL, PHYTOCONSTITUENTS, AND TRADITIONAL MEDICINAL USES OF SOME SELECTED SUDANESE PLANTS

Several pharmacological studies have demonstrated the antimicrobial activities of the medicinal plants, supporting its traditional uses. Phytochemical studies on these plants have demonstrated the occurrence of many classes of bioactive compounds, including flavonoids, terpenes, lignans, proanthocianidines, and chlorogenic acids, among others [Table 2]. In the following section, selected medicinal plants are described in more details with respect to the traditional uses, phytoconstituents, and antimicrobial activities.

Azadirachta indica A. Juss. (Meliaceae)

Azadirachta indica is widely used in folkloric medicine for the treatment of variety of diseases in remote areas of Sudan. For instance, the decoction of leaves and roots is used for snake, scorpion bites and intestinal spasm, respectively.[8] The infusion of the leaves is used for treating malaria, fever, and jaundice [Table 1].[10] Furthermore, the powder of the dried leaves is mixed with water and taken to treat freckles and to increase appetite.[297298] A. indica has also been scientifically proved for its antibacterial,[129] antiparasitic,[123] neuroprotective,[125] antimalarial,[86126] anti-inflammatory,[127] acaricidal,[121] and antinociceptive[127] effects. Several bioactive compounds have been isolated from different parts of A. indica [Table 2]. Nimbin and nimbidin representing the main phytoconstituents isolated from the seed of the plant, which have showed several biological properties including antibacterial, antifungal, and anti-inflammatory.[130]

Khaya senegalensis (Desr.) A. Juss. (Meliaceae)

Khaya senegalensis is extensively used as a traditional medicine in rural areas of Sudan for various ailments [Table 1]. Abuzeid et al.[299] described that chloroform extracts of the bark and leaf of K. senegalensis exhibited a significant inhibitory effect on Mycobacterium tuberculosis. Strong antibacterial activities for different bark extracts against Salmonella enterica, Staphylococcus aureus, Streptococcus pyogenes, Salmonella typhi, Shigella dysenteriae, Klebsiella pneumoniae, and Pseudomonas aeruginosa [Table 2] were also reported.[210] In addition, the plant has anti-inflammatory, antidiarrheal, antioxidant, antidiabetic, anticancer, and anthelmintic activities.[205206208209] The observed biological activities might be due to the presence of saponins, tannins, flavonoids, terpenoids, alkaloids, anthroquinones, limonoids, khayanolides, and p-anilinophenol, which have been identified in this plant [Table 2].

Ocimum basilicum L. (Lamiaceae)

Ocimum basilicum is considered as one of the major genera of the Lamiaceae family. It grows in several regions all over the world. In Sudan, O. basilicum grows in the wild and is also cultivated in Northern and Central Sudan.[30] Traditional healers in the remote areas of Sudan use O. basilicum in the form of infusion against jaundice and as demulcent.[89] The essential oil of the plant is used in perfumery and in food industry as flavoring agent, as well as in dental and oral products.[300301] O. basilicum has shown several biological properties, including antimicrobial, antimalarial, and antioxidant activities.[282284288] These pharmaceutical activities could be attributed to essential oil constituents, such as eugenol, linalool, camphor, methyl chavicol, and methyl cinnamate [Table 2].

Calotropis procera (Ait.) Ait. f. (Asclepiadaceae)

Conventionally, in Sudan, Calotropis procera is used in the form of infusion to treat jaundice, thorn injuries and as mouth detergent, while the paste of the plant is used against scorpion bits and rheumatic pain [Table 1]. C. procera has shown antibacterial, antioxidant, antifungal, and anthelmintic activities.[157159160161] Saponins, tannins, alkaloids, flavonoids classes of compounds are likely to contribute to the reported effects.[162]

Hibiscus sabdariffa L. (Malvaceae)

H. sabdariffa is considered one of the medicinal plants having great interest among all Sudanese communities. It has been used in ethnomedicine as herbal drinks in cold and hot beverages and as an herbal medicine. H. sabdariffa natural habitat is Southern Sudan, but it is cultivated in many parts of the Sudan. The maceration and decoction of the plant are used against hypertension, colds, fever and as antispasmodic and antimicrobial agent [Table 1]. In addition, H. sabdariffa calyces are boiled with sugar to produce a drink known as “Karkade.” Pharmacological studies have demonstrated that H. sabdariffa extracts showed antibacterial,[240] antioxidant,[242] antidiabetic,[244] anticancer,[60245] antihypertensive,[246] antipyretic,[241] anti-inflammatory,[98] and hepatoprotective effects.[243] However, the plant extract did not inhibit the growth of fungus Candida albicans.[240] The interesting biological effects might be associated with the presence of phenolic acids, organic acids, and anthocyanins reported in different parts of the plant.[61]

Ziziphus spina-christi (L.) Desf. (Rhamnaceae)

Z. spina-christi is a tropical tree of Sudanese origin. The plant has very interesting historical and religious aspects. It is repeatedly mentioned in Muslim as well as Christian traditions and was recorded by pilgrims visiting the Holy Land on numerous occasions. The boiled water extracts of the leaves of Z. spina-christi are used by Muslims in the cleaning of a dead body before burial suggesting antibacterial properties. In addition, the plant has been used in mummification by the ancient Egyptians.[302303] It has been suggested that the plant material referred to in the Bible as the “bramble” or “thorns” (Judges 9; 14-15), “thorns” (Matthew 27:27-29), and “crown of thorn” (John 19:5) might have been derived from Z. spina-christi.[304305] The Holy Quran mentions the Lote tree (Cedar) 3 times (XXXIV: 16; LIII: 13-18; LVI: 28-32), which was frequently identified as Z. spina-christi. Accordingly, this species is highly respected throughout the Middle East, has been widely used as a food and as medicinal as well as an environmental protection plant since ancient times, and is still in use until now.[305306307]

Z. spina-christi is commonly used in ethnomedicine for the treatment of many illnesses such as digestive disorders, weakness, hepatic disorders, obesity, urinary problems, diabetes, skin infections, fever, diarrhea, or insomnia.[308309] In Sudanese ethnomedicine, the leaves of Z. spina-christi are used for the treatment of malaria.[23] In addition, Michel et al. reported an antidiabetic activity of the leaves of Z. spina-christi due to their saponin and polyphenol contents,[310] which was supported in pharmacological studies by Glombitza et al., indicating that extracts of Z. spina-christi leaves or its main saponin glycoside, christinin-A, improved glucose utilization in diabetic rats.[311] Furthermore, Z. spina-christi leaves and fruits are reported to possess antibacterial activity,[312313] as well as antifungal activity on plant pathogens.[314] In addition, Adzu et al. found that root bark extracts showed significant antinociceptive activity in mice and rats.[315]

The phytochemical studies of the Z. spina-christi have demonstrated that peptide and cyclopeptide alkaloids such as spinanine-A, tanines, essential oil such as geranyl acetate, methyl hexadecanoate, and methyl octadecanoate, sterols such as β-sitosterol, triterpenoid sapogenins, and saponins such as betulinic acid, flavonoids such as rutin and quercetin derivatives are the main phytoconstituents of this plant.[316317]

Mimosa pigra L. (Fabaceae)

Mimosa pigra (giant sensitive plant) is a woody shrub, native to the American tropics. Besides its native area, it is very invasive and damaging and affecting agriculture and conservation. In particular, it is problematic in Australia, Africa, and Southeast Asia.[318] It has been introduced to Sudan and its neighboring countries.[319] Apart from this, M. pigra is used in the traditional medicine in tropical Africa, Indonesia, Madagascar, and South America for heart problems, head colds, diarrhea, toothaches, eye medicine, and its antimicrobial activity.[320321] Rakotomalala et al. demonstrated the beneficial effect of the leaves of the plant for pulmonary hypertension.[322]

Different phytochemistry constituents including tryptophan, myricetin 3-O-rhamnoside, quercetin 3-O-hexoside, quercetin 3-O-pentoside, quercetin 3-O-rhannoside, kaempferol 3-O-rhamnoside, kaempferol, apigenin, acacetin, quercetin 3-rutinoside, quercetin 3, 7-dirhamnoside, kaempferol 3,7-dirhamnoside and luteolin 7-arabinoside, quercetin 7-methyl ether, and saponin have been previously described as occurring in M. pigra.[322323324]

Ixora coccinea L. (Rubiaceae)

Ixora coccinea is a flowering plant native to India and Sri Lanka. I. coccinea is used in traditional Sudanese and ayurvedic medicinal systems for the treatment for diarrhea, fever, headache, skin diseases, eye trouble, wounds, sores, and ulcers.[325] Recent reports show that I. coccinea has antioxidant,[326] antibacterial,[327] anticancer,[328] analgesic, anti-inflammatory,[329] antidiarrheal,[330] hepatoprotective,[331] cardioprotective,[332] antimutagenic,[333] wound healing,[334] and anticancer activities.[335] I. coccinea is a source of peptides,[336] triterpenoids,[337] and fatty acids.[338] Recently, we have reported different phenolics in the stem and leaves of I. coccinea including chlorogenic acids, proanthocyanidins, flavonoids, and flavonoid glycosides,[339] in addition to the similar bioactive compounds identified previously.[340]

Ambrosia maritima L. and Sonchus oleraceus L. (Asteraceae)

Ambrosia maritima and Sonchus oleraceus, two multipurpose medicinal plants, are widely distributed weed in Sudan, Senegal, and neighboring countries.[341342] These plants are extensively used to treat several diseases including virus infections across the African continent.[22341342] In Sudan and other countries, A. maritima dried herb is used for treatment of hypertension, diabetes, bronchial asthma, spasms, frequent urination, urinary tract infections, and elimination of kidney stones.[17343344] This plant is also applied as a molluscicidal component for controlling of the intermediate hosts of Fasciola and Schistosoma.[345] Moreover, some authors have previously reported the antiviral and antifungal activities of A. maritima.[22341] On the other hand, the vegetative shoots of S. oleraceus have been frequently used by traditional healers to treat diabetes, diarrhea, pneumonia, and hepatitis.[342346] Moreover, the plant has cholagogue, laxative, and emollient properties.[347] The antidiabetic, antibacterial, anti-inflammatory, and antioxidant properties of S. oleraceus were also reported.[342348349350351] Several bioactive phytoconstituents have been identified in A. maritima and S. oleraceus including phenols, flavonoids, proanthocyanidins, alkaloids, tannins, terpenes, and steroids.[341349351352353354355356]

CONCLUSIONS

In this review, we have showed that local people in Sudan are still relying on traditional medicines to treat several diseases and microbial infections. The information collected in this article demonstrated the existing traditional uses of the most important Sudanese medicinal plants and summarized recent research into the phytochemistry and pharmacology of these plants. The extracts and isolated compounds have been found to possess various biological activities, particularly in the area of antimicrobial, antidiabetic, anticancer, anti-inflammatory, and antioxidant. Although increasing interest has encouraged more studies on the phytochemistry and pharmacology of the Sudanese medicinal plants, there are still many parts where the present knowledge could be improved, for instance, systematic toxicity and safety evaluation, the detailed quantitative data for the bioactive compounds and investigation the structure activity relationships of the isolated and purified active compounds. Moreover, most of the pharmacological studies on medicinal plants have been carried out in vitro. Thus, the effectiveness of plant extracts and isolated compounds needs to be further investigated for their efficacy and safety using in vivo assays; consequently, benefits could be fairly shared among Sudanese local peoples according to the CBD. It is concluded that traditional medicine should be considered seriously in future researches and projects designed to produce lead compounds and/or biologically active molecules from plant sources.

Financial support and sponsorship

Financial support from Deutscher Akademischer Austauschdienst (DAAD) is gratefully acknowledged.

Conflicts of interest

There are no conflicts of interest.