This review work tries to address on ethno botanical knowledge of Aloe plants in Ethiopia. There are 46 species of Aloe in Ethiopia in which about 66% of these Aloe species are endemic to the country. They are distributed in all floristic regions. Aloes are very important source of traditional medicine in Ethiopian communities to treat different ailments. In addition Aloes are used in soap production, jute sacks production, anti-microbial activities in cotton fabric, as thickening agent, degraded land rehabilitation and source of food for animals. Although there have been some attempts to conduct researches on Ethiopian Aloe species, the available information especially on commercial use, industrial use, propagation, germination and farming are insignificant and overlooked. As their distribution indicate Aloes are important component of Ethiopian dry-land ecosystem including pastoralist and agro-pastoralist area in which the amount of rain is low. In this area introducing Aloe farm system could be better alternative of poverty reduction and income generation. The presence of anthropogenic and environmental factors such as agricultural expansion into marginal lands, overgrazing, habitat destruction and restricted distribution may affect Aloe plants that could play great role in economic development for present and future generations of the country. As a result Aloe species need urgent conservation attention, effective documentation and further research.

Oda BK, Erena BA (2017) Aloes of Ethiopia: A Review on Uses and Importance of Aloes in Ethiopia. Int J Plant Biol Res 5(1): 1059.

•    Aloes
•    Importance
•    Diversity 

The Aloes are perennial plants that comprise herbs, shrubs and trees [1]. They are recognized by fleshy, strongly cuticularized leaves usually with spiny margins [2]. They are native to main land Africa south of Sahara except few species occurring in Arabian Peninsula and on small islands of the insular Africa. Hence, SubSaharan Africa, including the island of Madagascar accounts for over 90% of the 450 taxa (species, subspecies or varieties) of the genus Aloe known today. It has been suggested that the centre of origin for the genus is in the highlands of South East Africa [1,3], and the ancestral Aloes believed to spread during the Tertiary era. Although some species are very restricted in distribution, others are widespread and in the absence of competition, may become locally invasive. Southern Africa and Madagascar are particularly rich in endemic species [4].

Aloes are often thought to only grow in hot and dry climates but they actually grow in a variety of climates and ecosystems including desert, grassland, and coastal or even alpine areas. The genus occurs across a wide range of habitats, from dry forests to scrublands. The ecological range of Aloes generally excludes rain forest habitats, and except for species previously grouped under the genus Lomatophyllum, which do not occur in lowland moist forests. The range of altitudes is wide, from 0 m (Aloe massawana) to over 2300 m for Aloe juvenna. The highest proportion of Aloes (32%) occurs between 100-1500 m above sea level. Higher altitudes have been reported from some species in Ethiopia (e.g. A. ankoberansis). Aloe polyphylla, can be found as high as 11,500 feet above sea level in the Drakens berg mountain of Lesotho [5]. Aloes usually grow in the open and rarely found among shrubs or trees. They are also adapted to arid habitats through their succulent habit [4].

Aloe species are adapted to highly disturbed areas and areas with extreme environmental conditions; and are found flourishing on nutrient deficient soils. In most cases Aloes are found growing in rocky or gravelly soils, but they will also grow in richer soils among grasses, out of cracks and crevasses in rocks, or in sand. Aloe plants growing in shade are generally more robust than those growing on exposed grounds. However, judged by their successful cultivation in different soil mixtures, Aloes are apparently tolerant to many soil types [6].

Aloes are successful because of several important adaptations to their environments. They use a special kind of photosynthesis called CAM (Crassulacean Acid Metabolism) that minimizes water loss that would occur with standard photosynthesis in hot climates [7]. Another adaptation is an Aloe’s ability to store relatively large amounts of water in the leaves; so in times of drought they will have a supply to draw upon [8]. A waxy coating on the surface of the leaves of Aloes also helps with moisture loss by minimizing evaporation of water from cells on the surface of the leaves and limiting water loss through the stomata. The wax can also reflect excess light away from the plant. This wax can be seen on the leaves of most Aloes as a bluish color cast [7].

To deter herbivory by thirsty desert dwellers, Aloes have developed two important features. Most Aloes have spines along the margins of their leaves, and sometimes throughout the leaf surface, to prevent larger animals from chewing on the leaves. For smaller pests and those not deterred by spines, bitter exudates are produced just under the surface of the leaves. This is known as Aloe bitters, a substance that humans have been using for medicinal purposes for thousands of years [7]. The other important adaptation is the presences of brilliant flowers that have an excessive nectar production to attract pollinators, and winged seeds aid them for wind dispersal. These unique adaptations make the Aloes the important groups of plant in such environments in providing important source of shelter, nectar food, and moisture, especially to the avifauna [9,10].

Members of the genus Aloe has been known for their current and potential use in medicine, commerce and horticulture. They are said to be keystone species in ecological sense particularly in the dry-land ecosystem. Aloe species have been used for long time in folk medicine for treatment of constipation, burns, kill bacteria and dermatitis [11]. For instance, sap of Aloe lateritia is used in some communities of Kenya and Ethiopia for treatment of eye aliments [12]. Aloes are an important component of the dry-land ecosystems. They have great role in solving ecological problems. For example, A. secundiflora in Kenya have been used in fencing and hedging, soil conservation /compaction and ecosystem restoration (rehabilitation) [6].

According to Sebsebe Demissew and Nordal [10] and Sebsebe Demissew et al. [13], 46 species of Aloes are known from the flora area, out of which six have been described in the past seven years indicating active taxonomic research and targeted field surveys on the genus Aloe in the flora area. The six new species are all reported to be endemic (or, as in the case of Aloe clarkei, perhaps near endemic) to Ethiopia. This has raised degree of endemism of species of Aloe to 89%, indicating that the genus Aloe has high degree of endemism in the flora area. Very few, only five species are wide spread extending to East and West Africa. These are A. laterita, A. macrocarpa, A. rivae, A. secundiflora and A. vituensis of Ethiopia. It is also demonstrated that most endemic and near endemic species have very restricted distribution.

Though not yet investigated and exploited for their use as in other parts of Africa, Aloes in the flora of Ethiopia may have economic and ecological potential uses for current and future generation. As indicated by different researches Aloes of Ethiopia have different values such as: traditional medicines, soap production, manufacturing of soak for coffee export and degraded land rehabilitation. However, these important Aloe plants and their habitats are reported to be threatened in most parts of the flora area. The reasons for threats might be two folds: linked to ecology of the species area distribution or to the biology of the species such as reproductive success, dispersal efficiencies and other population attributes. Habitat destructions for agricultural expansion, urbanization, development construction such as roads and overgrazing are worth mentioning. Hence, we found it is imperative to compile information on uses of Aloes of Ethiopia as a basis for future investigation of their traditional and modern uses.

Distributions of aloes in Ethiopia

The account of family Aloaceae of the Flora of Ethiopia recognized 46 species. They are distributed in all floristic region of the country including: Afar, Arsi, Bale, Gamo Gofa, Gojam, Gonder, Harerge, Kefa, Shewa, Sidamo, Tigray, Wellega and Welo floristic regions [10]. Accordingly, majority of Aloe spp. found in Sidamo floristic region (with 14 species) followed by Harerge, Bale, Shewa, Tigray and Welo floristic regions (with 10, 8, 8, 7 and 7 species respectively). Whereas few species found in Afar and Wellega floristic regions (each possess one Aloe species) and one Aloe species (Aloe macrocarpa) found in many floristic regions including Arsi floristic area (Figure 1).

Sebsebe Demissew et al. [14], analyzed the distribution of Aloes of Ethiopia in relation to vegetation types, and showed that the endemic and near-endemic species occurred predominantly in two vegetation types. These are: (1) dry montane evergreen forest (and associated montane evergreen scrub or montane grassland), and (2) Acacia-Commiphora woodland and bushland. Some of the Aloes that occur in dry montane evergreen forest include A. debrana, A. adigratana, A. percrassa, A. pulcherrima, A. elegans, A. camperi and A. yavellana. AcaciaCommiphora woodland and bush-land also hosts Aloe species like A. calidophila, A. ellenbeckii, A. gilbertii, A. friisii, A. retrospiciens, A. mcloughlinii, A. pirottae, A. otallensis and A. trichosantha. Some of the Aloe species like A. bertemariae and A. citrine are reported from desert and semi-desert scrubland and A. ankoberensis is from Afro-alpine vegetation of Ethiopia [10]. The most surprising from ecological and phytogeographical points of view are A. benishangulana and A. ghibensis that seem to belong to a hitherto unrecognized western group mostly associated with firesusceptible Combretum-Terminalia woodlands [13].

Habitats of aloes in Ethiopia

Aloes are available in variety of vegetation types at various altitudes in the country. Thus most Aloes (about 48%) are found at elevation ranges of 1500-2500 m in middle altitude area. Some Aloes (about 34%) are found at altitudes of 500-1500 m in semiarid climate while other species of Aloe (about 14%) could be live between altitudes of 2500-3200 m in high altitude area. However, few Aloes (about 2%) survive at elevation ranges above 3200 m in alpine area whereas the other few Aloe species (about 2%) may live at altitudes below 500 m in arid climate (Table 1). Here, the alpine Aloes are found in Shewa floristic region and they are adapted to cold climatic conditions. Besides, the arid area Aloes are found in Harerge floristic region and adapted to survive in the hot arid climates.

Endemicity of Aloes in Ethiopia

The genus Aloe has high degree of endemism (89%) in Flora of Ethiopia. The high degree of endemism is incomparable with any other genus in the flora area that has similar species diversity [13]. Furthermore, out of the total species and subspecies of Aloe plants in Ethiopia, about 66% are endemic or near endemic to the country while about 34% are not endemic (Figure 2). These endemic Aloes are crucial for economic benefits of local communities and development of the country. Therefore, these plants require urgent conservation for sustainable usage in the future.

Most of endemic Aloe species have very restricted distribution area. According to Sebsebe Demissew and Nordal [10], four centers of endemism have been recognized in the flora area: 1) Northern and central highlands, north and west of the Rift Valley that comprises 16 endemic species (e.g. A. adigratana, A. camperi, A. sinana, A. pulcherima, and A. debrana); 2) Eastern and south east highlands and lowlands that includes 9 species restricted to the eastern highlands (e.g. A. elkerriana, A. harlana, A. mcloughlinii and A. welmelensis); 3) Southern part of Ethiopia that contains 6 endemic taxa (e.g. A. gilbertii, A. otallensis, and A. friisii); and 4) Western parts of Ethiopia that includes 4 species (A. clarkei and A. kefaensis, and the newly described A. benishangulana and A. ghibensis)

Table 1: The habitat elevations of Aloe plants in Ethiopia.

Medicinal values of Aloe species

Most Aloes produce a bitter exudate just under the surface of the leaves. This Aloe bitter is a substance that humans have been using for medicinal purposes for thousands of years [7]. Members of the genus Aloe has been known for their current and potential use in medicine, commerce and horticulture. Aloe species have been used for long time in folk medicine for treatment of constipation, burns; kill bacteria, dermatitis, diseases connected with the digestive system; wounds and skin problems [11,15]. The medicinal role of Aloe specie believed to be due to the synergistic action of different compounds constituent. These chemical compounds include inorganic minerals like ions of calcium, magnesium, zinc, iron, copper etc., saccharides namely arabinose, galactose, glucose, mannose and xylose, some twenty amino acids, vitamins B1 , B2 , B6 , B12 and C. etc. and enzymes such as amylase, lipase, folic acid, etc. [16].

In Ethiopia, Aloe spp. such as Aloe trichosantha Berger, Aloe pubescens Burger, Aloe citrina Carter & Brandham, Aloe bertemariae Sebsebe & Dioli, Aloe eumassawana Carter, Gilbert & Sebsebe and Aloe schoelleri Schweinfurth “have been used in a wide range of skin and hair care products; also they form the basis of health drinks and tonics” [17]. In rural parts of the country, its mucilaginous fluid applied to cuts and wounds in order to prevent infections and bring about healing [18]. Recent ethnobotanical studies have been reported the use of various Aloe species as traditional medicines in our country (Table 2).

Commercial values of Aloe species

Different products can be extracted from various parts of Aloe plants which include flowers, leaves, stems and roots. Aloe calidophilla is identified to be one of the commercially important species [6]. In the Borana community, the sap/exudate from the most popular Aloe calidophila, Aloe Scandiflora and Aloe Scabrifolia processed for their soap. Roots of Aloe secundflora are used in fermentation process [36]. Moreover, Aloe vera, Aloe ferox Mill. (Found in South Africa), Aloe arborescens Mill. (South Africa, Malawi, Mozambique and Zimbabwe) and A. marlothii Berger (South Africa) have been of commercial interest. For instance, Aloe vera is added to commercial creams and lotions to soften and moisturize skin and to other products for a variety of reasons [18].

In Ethiopia, especially in Southern Ethiopia, including parts of Somali Region and Oromia region (Borana and Guji Zones), wild Aloe species grow over vast areas. However, there is very little awareness of the commercialization of this ample resource by residents and transient communities. Currently there is no commercial harvesting, production, handling and processing of indigenous Aloe species. But a few Bio-enterprise developments in sustainable wild harvest and domestication of indigenous Aloe species were established by the help of Oxfam Canada in Borana Zone. This is aimed to contribute the poverty reduction, economic empowerment and social wellbeing of pastoralists, particularly women. They domesticate Aloe for healthcare and body care products. Nowadays three villages in the zone engaged in harvesting Aloe jell, producing soap from Aloe and marketing Aloe soap. In this areas about three species of Aloe are identified, which have been found to have compounds similar to those in Aloe vera, and have comparable leaf sizes making them good candidates for commercial exploitation. These Aloe species are Aloe yavellana, Aloe turkanensis and Aloe secandiflora. They are found in abundance and being used only by bio-enterprise [37].

Aloe plants in industry

The extract oils of different Aloe species found in Central Highland of Ethiopia like Aloe sinana, Aloe trichosantha, Aloe ankobernsis, Aloe debrana, Aloe pulcherrina, Aloe schelpei, Aloe camperi and Aloe weloensis were checked and identified for production of jute sacks. But only Aloe debrana and Aloe trichosantha plants allowed for the company by Ethiopian Biodiversity Institute, because others are rare. The natural oil of these two Aloe species is currently used in production of jute sacks for packing coffee, cereals and oil seeds. The use of batching oils on raw fibers which contain certain amount of hydrocarbon minerals become a problem in fiber producing company. This is due to the use of mineral oil based batching in the process of manufacturing jute bags used for packaging of food grade materials had been a matter of concern for the final consumers because of alleged and possible hydrocarbon contamination of the bags. As a result, currently the fiber company started using naturally earned oils from Aloes, especially, in manufacturing of soak for coffee export [38].

Recent researches indicate that extracts of Aloes can be used in different industries and can contribute for the future development of various industrial developments in the country. Some Aloes of Ethiopia are tested for different industry inputs in the future: for example, the extract of Aloe barbadensis for antimicrobial activity in cotton fabric, i.e., controlling Staphyllococcus aureus [39], the in-vivo anti-malarial activities of Aloe debrana was test and it showed positive results [40], Aloe debrana was also examined as good thickening agent for printing polyester and cotton with disperse dyes [41].

Ecological uses of Aloe species

Nowadays, Aloes are recognized as an important component of the dry-land ecosystems where they are associated with species such as Acacia, Kleinia, Cissus and Euphorbia. It has been suggested that Aloes may be primary colonizers of habitats that enable later habitation by other less resilient plants. Areas which experience prolonged drought can benefit from the planting of Aloe [42]. Observations made on A. secundiflora have shown that vegetation diversity, litter cover, soil retention and soil seed bank are greatly enhanced in the immediate vicinity of the plants [6,43].

Aloe shrubs increase the survival and growth rate of newly planted Cenchrus ciliaris grasses. This native species has already proved invaluable in saving rangeland in Kenya and Southern Ethiopia [42]. The presence of A. secundiflora creates microhabitats for associated plants and animals probably due to the physical protection, shade and perennial ground cover. Aloe shrubs are also known to improve soil conditions around them and to encourage the range of other plant species in the local area [6,43]. Furthermore, because of their demonstrable efficacy in rangelands rehabilitation, the Aloe plants benefit the environment in other ways [42].

Aloes are an important component of the dry-land ecosystems of Ethiopia. They have great role in solving ecological problems. For, example, A. gilbertii plant and its parts for various purposes among others, its uses in the rehabilitation of degraded land and soil conservation efforts were widely mentioned. The whole individuals were transplanted by local community to the areas surrounding their farm lands, range lands and home gardens for the purpose of demarcation and protection in the form of area enclosure, in hedging and fencing. It was also widely observed that individuals of A. gilbertii are planted along slopes in bund, terracing or ditch formation against soil erosion and for soil retention during erosion [33]. The existence of Aloe macrocarpa is used as a fence for home, farm land and range land [21]. Aloe debrana plants are also very important in soil and water conservation [38].

Aloe as a food of animals

Aloe species are important source food for animals and various birds. Aloes produce large amounts of nectar. They have long tubular, most often red to yellow flowers, producing considerable amounts of nectar, all traits indicating typical adaptations to bird pollination. The different Aloe species have different flowering periods; some flower over an extended period, thereby offering a continuous food supply for nectar feeding birds. Accordingly, the Aloes make an important contribution to the bird biodiversity of Ethiopia, especially for the sunbirds. At the same time, the birds are vital for the pollination of the flowers and seed set [10]. In relation to honeybees, the presence of flowering Aloes has been observed to enhance the quantity and quality of honey output over the seasons [6]. This indicates the importance of Aloes as honey bee forages.

Table 2: Use of Aloe species as traditional medicine in Ethiopia.

Many species of Aloe are threatened for various reasons. These include habitat destruction caused by urban and regional development constructions, and over collection for their use in pharmaceutical and cosmetic industries. Another important concern is that many species have very restricted areas of distribution and occur only in small populations. The Aloes may also be a target for succulent enthusiasts in their quest for rarities [10]. Moreover, out of 46 Aloe plants of Ethiopia, 18 species are listed as threatened species [4]. These threatened species require urgent conservation in order to transmit them for next generations. Therefore, wisely use of these plants will be advisable during harvesting for medicine, cosmetics, soap, fibers, food, etc. in order to use sustainably in the future.

Conclusion

Despite the large abundance of Aloes in Ethiopia both in terms of distribution and species number, information on their uses and research are very limited. The available research information in Ethiopian societies is insignificant and indicates the need for further investigation in all regions of the country. In addition, taking further study on economic use, commercial use, industrial use, conservation, farming and domestication of Aloes is very important issues for future uses of Aloes in economic development of the country.

Ethiopia is one the developing countries, in which many people get low income per capital. Since Aloes are abundant and available in different part of the country, they may serve as good source of income like Aloe vera in other countries. Therefore, Aloes could be potential resource in local uses and as export commodity to generate income. Although Ethiopian Aloes have different importance, they are threatened by many anthropogenic and environmental factors like habitat loss and degradation; hence urgent conservation attention is needed to conserve Ethiopian Aloes for sustainable usage in the future.

Recommendation

Although Ethiopia is rich in medicinal, commercial and ecologically important Aloe species, there is no widely use of these plants in modern way. However, modern drugs, cosmetics, soap, fibers and food can be manufactured from Aloe species industrially. Therefore, the practice of manufacturing Aloe products should be developed through further experimental investigations on medicinal, cosmetic, nutritional and other uses of Aloe species in our country.

In addition, even if Aloe species are such crucial in our country, some species are threatened due to lack of awareness, urban expansion, agricultural practices and uses as traditional medicinal plants. Also they are not well conserved and have not got more emphasis by local communities. Therefore, the local people should participate actively in conservation and protection of Aloe species in their local area.

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