COMMON ANTIMALARIAL TREES AND SHRUBS OF EAST AFRICA

COMMON ANTIMALARIAL TREES AND SHRUBS OF EAST AFRICA

The Purpose of this guide

The purpose of this guide is to describe a range of trees and shrubs that are used as antimalarial treatments in East Africa. Malaria is a significant problem in the region, with 15 million cases reported in Kenya in 2006, 11 million cases in Tanzania over the same period and 12 million in Uganda in that year. At the same time, access to modern treatments for the disease is limited, with only around 8% of children under five years old that contracted malaria being treated with ACTs in Kenya in 2007. Simillarly, only 22% of such children were treated with ACTs on the Tanzanian mainland in 2008, and only 3% of infected under fives received such treatment in Uganda in 2006 (data available for certain years only). Reported cases and deaths caused by malaria in these three countries are shown in the given graphs and indicate the serious extent of the disease.

The 22 tree and shrub species chosen for description here have been assigned by traditional medical practitioners, rural communities and scientists as among those that have potential for further study and development as crops by smallholders in East Africa, although this list should not be considered as exhaustive of all useful antimalarial plant species in the region. Extract from a few of the species described inthis guide (e.g., Artmisia annua, Azadirachta indica and Warbugia ugandensis) are already more widely used commercially for treatment (and/or prevention) of malaria, especially of course artemisinins.

Erythrina abyssinica DC.
Pilionaceae(Indigenous)

Common names: Flame tree, Lucky bean tree, Red hot poker tree. Local names: Muvuti (Kam), Muthuti (Kik), Olepangi (Maa-Ken), Muuti (Mer), Mwamba-ngoma (Swa-Ken), Miriri (Chag), Ol-ngaboli (Maa-Tan), Mkalalwanhuba/Pilipili (Suk), Mjafari (Swa-Tan), Munyirikiti (Lug), Oluo/Olugo (Lugb), Cheroguru (Lugi)

Botanical description and ecology:
A deciduous tree with a short trunk and thick spreading branches and rounded crown, to 12 m in height. Bark yellowish brown, thick, corky and fissured, with or without woody spines. Leaves compound, with three leaflets, broadly ovate. Flowers orange-red heads. Fruity woody pods, straight or curved, upto 10 cm long with bright red seeds with a black patch. Found throughout East Africa, commonly occurring in open savannah woodland, grassland and scrubland; not found in very dry areas; altitude ranges from sea level to 2000 m.

Uses: Timber to make doors, furniture (stools), beehives, carvings, utensils (mortars, drums), fuelwood, medicine (human and veterinary use), bee forage, ornamental, mulch, soil fertility improvement and soil conservation.

Traditional Medicine: Root and stem bark decoction is used to treat malaria and syphilis [1,2,3]. In paste form, powdered bark is applied to burns and is used for general body swellings, rheumatism and arthritis [2,3]. Extract of the dried leaves in water is used for the treatment of leprosy (applied externally) [3,4] and fever (taken orally) [5].

Active compounds reported and antiplasmodial activity: Several tetracyclic isoquinine alkaloids (known as Erythrinan alkaloids) have been reported from the seed, root and flowers of Erythrina species [6,7]. Typical compounds isolated from the roots of E. abyssinica are flavanones (e.g., abyssinone IV) and pterocarpans (e.g., phaseollin) [8]. The stem bark also contains flavanones such as 5-deoxyabyssinin II [3,9]. The ethyl acetate extract of stem bark shows antiplasmodial activity: a new chalcone (5-prenylbutein) and a new flavanone (5-deoxyabyssinin II) are among the antiplasmodial principles [9]. The crude extract of the roots is more potent, with the flavanone abyssinone IV and V being the most active [10].

Cultivation: Erythrina abyssinica grows easily from truncheons (2.5 m long and 8 to 10 cm in diameter) that are stripped of leaves and are planted at the onset of the rainy season. Propagation may also be carried out by direct sowing, by raising potted or bare-rooted nursery seedlings, and from cuttings. Seed may be stored for long periods without loosing viability if kept cool, dry and insect free. Seed that have been damaged by insects should be discarded. On average, there are around 6,800 seeds per kilo.

Seed have hard coat that should be scarified before germination in order to allow moisture to penetrate. This will lead to more uniform germination of a seed lot. Seed can be scarified by rubbing with sandpaper or nicking the distal end of each seed. Seedshould be immersed in cold water for 24 to 48 hrs after scarification, until they begin to swell. Alternatively, pour warm water over scarified seed and stand for 12 hrs.

Immediately before planting, seed should be inoculated with rhizobium bacteria to ensure nodulation and nitrogen fiixation. Seed can be germinated in trays or may be sown directly into nursery beds or pots, using a mixture of soil, sand and compost (in ratio of 2:1:1). Seed should be sown just below the surface, with hillum facing downward. Nursery-grown plants are ready for transplanting when 20 to 30 cm tall. If using bare-rooted seedlings that have been raised in nursery beds, all leaves should be removed before planting.

Growth of the species is slow. Pollarding and coppicing are suitable treatments, although trees should not be pruned until they are one year old. Frequent pruning reduces competition with crops and increases the ratio of leaves to stems, but increases labour costs. It may be advisable to grow the tree with shade-tolerant crops, rather than imposing a severe pruning regime. With its soft wood, the species is somewhat easier to prune than other species used in alley farming. In Kenya, the species is often used to make cattle enclosures, and living fences are established from cuttings.

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