A REVIEW OF COMMERCIAL GUMS AND GUM RESINS RESOURCES IN : , ECOLOGY AND DISTRIBUTION Francis N. Gachathi and Meshack O. Muga KEFRI P.O. Box 20412, Nairobi E-mail: fgachathi @yahoo.com

Abstract Gums and resins are among the natural resources in Kenya with potential for generating wealth and uplifting the living standards of the local communities in the drylands. The quality of Kenyan gums and resins is however affected by various factors that include, botanical origin and mixing of different species. Effort is therefore required to address issues related to improvement and production of commodities from these resources, among them, correct species identification. The objectives of this study are to identify by botanical and local names and describe; that produce commercial gums and resins, their ecological preference and distribution; species that are most similar to and likely to be confused with them and other species that produce similar gums or resins that could be possible adulterants. The study area was Northern Kenya and involved field discussions and site visits with gums and resins collectors and traders and examination of collected products at collection centers. Commercial gum arabic is obtained from Acacia or A. seyal while gum resins are from myrrha, hagar from C. holtziana and frankincense from Boswellia neglecta. Species that are likely to be confused with A. senegal are A. condyloclada, A. hamulosa, A. ogadensis, and A. thomasii while those likely to be confused with A. seyal are A. zanzibarica, A. xanthophloea and A. hockii. Possible adulterants of gum arabic are A. paolii and A. mellifera while resins are usually adulterated with C. africana, Commiphora confusa, C. habessinica, C. schimperi, C. pseudopaolii, C. kua var. gowlello and C. incisa.

Keywords: Gums and gum resins, taxonomy, ecology, distribution

1 Introduction Gum arabic comes from Acacia senegal (L.) Willd. or Acacia seyal Del. while main gum resins in Kenya are myrrh from Commiphora myrrha (Nees) Engl., Hagar from C. holtziana Engl. and frankincense from Boswellia neglecta S. Moore. These are trees and shrubs that are dominant and form an important component of the vegetation in the drylands often referred to as Acacia-Commiphora woodland.

In general acacias are very distinctive and easily recognized by their characteristic thorns, feather-like and pods. They are popularly called "thorn tree" while most shrubs with hooked spines are called "Ngoja kidogo" meaning wait-a-bit. Commiphoras are medium sized trees that are recognized by their peeling outer bark and aromatic exudate, compound leaves usually clustered at the ends of the short and spiny-tipped shoots and fleshy fruit, splitting when ripe into 2, disclosing a red, orange or yellow outgrowth of the seed. Boswellias are closely related to Commiphoras, they are generally short trees or shrubs with their outer bark often peeling in papery flakes from the greenish under bark. Their leaves, which are compound, are usually clustered at the ends of the branches. Fruits are angled, opening when mature with the valves dropping and leaving a central winged column with the seeds attached.

Gum arabic The Joint FAO/WHO Expert Committee on Food Additives (JECFA) defines gum arabic as the ‘dried exudation obtained from the stems and branches of Acacia senegal or A. seyal (FAO, 1998). In its natural state, it comes in a variety of shapes, colours and sizes. The colour of the gum may vary from colourless through different shades of yellow, amber, orange, red and dark brown. The best grades from A. senegal are in the form of whole, round tears, orange-brown in colour and with a matt surface texture. Gum from A. seyal is more friable than that produced by A. senegal and is rarely found as whole lumps. Use of gum arabic falls into three main sub-sectors: food industry, pharmaceutical industry and technical areas such as printing, ceramics and textile industries (Chikamai and Odera, 2002).

2 Myrrh Myrrh is the gum-resin exudate from the stems of Commiphora myrrha. It oozes and hardens to form lumps of varying shapes and sizes of variable colour from red, brown to dark brown. Locally, it is used to make ink used in Quranic schools, burning to repel snakes and offensive insects and medicine for various ailments. Its commercial uses are mainly essential oils, cosmetics, flavours, antiseptics and other medicines.

Hagar (opoponax) Hagar is oily resin exudate from the stems of Commiphora holtiziana. It oozes out and hardens to form lumps of various sizes and shapes with variable colour from yellow to dark brown or black. Locally, hagar is used as acaricide against ticks, snake bites, scorpions, foot rot, mange and other livestock ailments. Commercially, it is a well- established herbal medicine and essential oil in cosmetics.

Frankincense Frankincense is the exudate from the stems of Boswellia neglecta. It oozes out in small droplets that harden to form nodules or large lumps. It is of two types, black and white. Locally it is used as chewing gum, burnt as incense, perfume and medicine for a wide range of ailments. Commercially it is used as essential oil in perfumery, cosmetic as well as flavour industries.

Recognition of A. senegal Acacia senegal is generally recognized by its three hooked prickles, central one curved downwards and the two laterals more or less curved upwards, or singly, the laterals being absent and with the in spikes. These characters are however shared by a number of other Acacia species and A. senegal forms part of this complex group of spicate- flowered acacias with prickles in threes or singly (not in pairs). These species are closely related to and are often confused with A. senegal.

3 General description of A. senegal A shrub or tree usually 2-15 m tall. Bark on trunk yellowish to grey or greyish-brown, rough or smooth and papery and peeling off. Crown variable, loose and round to dense and flattened, sometimes open with long whippy branches. Young branchlets glabrous to densely pubescent. Prickles 2-8 mm long, in threes, with the central one curved downwards and the two laterals more or less curved upwards, or singly with the laterals absent. Petiole usually glandular. Pinnae 2-6(-12) pairs, with glands on the rhachis between the top 1-5 pairs of pinnae. Leaflets 7-25 pairs per pinna, glabrous to somewhat pubescent, 1-7 mm long, 0.5-2 mm wide. Flowers whitish or yellow-white, more or less scented, in spikes 2-10 cm long. Pods dehiscent, straight, grey to brown or yellowish- brown, pubescent, oblong or elliptic, 3-14(-19) cm long, 1.3-3.4 cm wide. Seeds (2-)4-8 per pod, more or less transverse.

The local names associated with A. senegal include: Ekunoit (Turkana), Edad, Adad (Somali), Idado (Borana), Ol-derekesi (Maasai), Lolderikesi (Samburu), Chemangayan (Pokot), Bura-dima (Orma), Mirgi (Rendile), Mung'ole (Kamba).

Variation within A. senegal The first description of a variety of A. senegal dates as far back as 1896 (Brenan, 1953). However, our current understanding about the existence of different varieties is credited to Brenan (1959) while a more comprehensive treatment of the different varieties of A. senegal was given by Ross (1979). Within the species, four varieties are currently recognized: typical var. senegal Brenan, var. kerensis Schweinf. (1896), var. leiorchachis Brenan (1953) and var. rostrata Brenan (1953). This last variety occurs in southern Africa. Beentje (1994) finds it very difficult to separate the varieties supposed to occur in Kenya and prefer to see the species as a single, quite variable one. Dharani (2006) recognizes var. senegal and var. leiorhachis as the only varieties in Kenya. In the field the habit and the habitat of the three varieties are strikingly different and are probably the most essential diagnostic characters by means of which the taxa can be identified correctly (Gachathi, 1994).

4 Typical var. senegal is recognized as a tree with a flat or rounded crown and rough non- papery and non-peeling bark commonly growing on sandy alluvial loamy soils in plains or at the foot of hills in semi-humid to semi-arid areas of Nakuru, West Pokot, Kajiado, Kitui, Isiolo and Baringo Districts.

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var. senegal var. kerensis var. leiorhachis var. leiorhachis (A. circummarginata)

Var. kerensis grows as a single or several-stemmed shrub with lateral branches from near the base and with smooth yellowish-brown peeling bark on the stem. It is found in the very dry areas, common on rocky limestone hills and ridges and on sandy plains frequently forming almost pure stands over large stretches of land in Turkana, Samburu, Isiolo, Marsabit, Wajir, Garissa and Mandera Districts. Most common at areas between 400-1130 m elevation and with 300-550 mm rainfall. This is the main gum arabic producing variety.

Var. leiorchachis exhibits two growth forms; either as a straggling slender tree starting with a very branched bushy base then thinning out to 1-4 slender whippy erect tall stems with peeling bark or a well grown tree with open rounded spreading crown and yellowish papery and peeling bark on the main trunk. The whippy form occurs in clusters of small populations on extremely rocky gneiss-derived sandy soils in semi-arid to arid areas in plains. Populations of this variety are found at Marti in Baragoi Division of Samburu District, along Magadi road in Kajiado and in Garba Tula. The tree with round crown formation (synonym A. circummarginata Chiov.) occurs on red deep sandy soils along

5 drainage lines and areas with high water table. It is common in Wajir, Marsabit and Samburu Districts.

Species likely to be confused with A. senegal The best description of the relationship between A. senegal and other species constituting the A. senegal complex is given by Ross (1979). Following are species found in Kenya that are most similar to and likely to be confused with A. senegal. Under each is given its local names, distribution and preferred habitat and the principal distinction from A. senegal.

A. condyloclada Chiov. Adad Geri (Somali) Found in Mandera, around Ramu, in Acacia-commiphora bushland on limesone slopes, 450-800 m. The white peeling bark, long internodes, large basal petiolar gland and few pairs of large leaflets per pinna distinguish A. condyloclada from A. senegal.

A. hamulosa Benth. Ethad (); Osatari (Orma) Found in Garissa and Tana River areas in dry bushland, 150-1200 m. The presence of a recurved prickle either at or near the apex of the lower surface of each rhachilla distinguishes A. hamulosa from A. senegal.

A. ogadensis Chiov. Adad Geri (Somali) Found in Mandera, around Ramu, in Acacia-commiphora bushland on limestone slopes and rocky areas, 400-500 m. The presence of fewer pairs (2-4) of broad (5-15 x 3-9 mm) leaflets per pinna distinguishes A. ogadensis from A. senegal.

A. thomasii Harms Ol-derkesi (Maasai)

6 Found in Kajiado, Taita, Kitui, Meru, Tsavo East. Occurs in small groups in Acacia- Commiphora bushland, 350-1200 m. The elongated whip-like branches and large flowers distinguish A. thomasii from A. senegal.

Recognition of Acacia seyal Acacia seyal is recognized by its smooth stem, which is covered with whitish, greenish yellow or orange-red powdery layer, bright yellow flowers in heads and the sickle-shaped dehiscent pods that are constricted between the seeds. These characters are however shared by other Acacia species with yellowish bark and capitate yellow flowers and could be confused with A. seyal. The species has two varieties: var. fistula (Schweinf.) Oliv. and var. seyal Oliv.

var. seyal

var. fistula

Acacia seyal Tree

General description of A. seyal A small to medium-sized tree, 3-12 m tall, with a flat crown or several-stemmed shrub. Bark smooth, covered with white to greenish-yellow or orange-red powdery layer, inner bark green. Thorns in pairs, straight, up to 8.5 cm long; in var. fistula, some spines swollen and fused basally into bilobed greyish “ant-galls’. Leaves with 2-8 pairs of pinnae; leaflets 11-20 pairs, 3-6 x 0.7-1.5 mm. Flowers in heads, bright yellow. Pods brownish, falcate, often constricted between the seeds, dehiscent.

7 Acacia seyal is usually found in colonies in wooded grassland, especially on seasonally flooded flats of black cotton soils, along water-courses, and on stony ground at the base of hills. It is very widely distributed, occurring in all districts except coastal areas. It is most common between 550–2000 m a.s.l.

The local names associated with this species include: Wacho-dima (Borana), Mgunga (Swahili), Waacu (Gabra), Kinyua, Kisewa (Kamba), Ole-rai (Maasai), Lerai (Samburu), Fullai, Jikh (Somali), Ekoromait (Turkana), Rena (Pokot), Lelnet (Tugen).

Species likely to be confused with A. seyal Following are species that are most similar to and likely to be confused with A. seyal. Under each is given its local names, distribution and preferred habitat and the principal distinction from A. seyal.

Acacia zanzibarica (S. Moore) Taub. Mpiga-Mruru (Swahili), Wacho (Borana), Muwachyu (Malakote), Musewa (Kamba), Waachu (Orma), Fulai, Jikh (Somalia).

Commonly found in Wajir, Isiolo and Tana River Districts. Often in wooded grassland, edge of saline-water swamps, river valleys and low-lying areas with high ground water, from sea level to 850 m. The species could be confused with A. seyal but the large leaflets 2-13 x 0.5-6 mm coupled with few pinnae1-4 pairs, distinguish it from A. seyal var. fistula.

Acacia xanthophloea Benth. Naivasha thorn, Fever tree (Common), Hwacho dima (Borana), Kimweya, Musewa (Kamba), Murera (Kikuyu), Ochmnyaliliet (Kipsigis), Olerai (Maasai), Mwelela (Taita).

Common around Nairobi, Naivasha, Kajiado, Nakuru and Narok areas. Often growing together where the ground water table is high, beside lakes or rivers, on black cotton

8 soils, 600-2300 m. Its yellow bark confuses with that of A. seyal but the straight indehiscent pods distinguish it from it.

Acacia hockii De Wild. Munga (Kamba), Oriang’ (Luo), Katet, Lendet (Kipsigis), Lerai (Samburu), Echekereng (Turkana), Enchapalani, Oljarpalani (Maasai).

Common in Kajiado, Narok, Nakuru, Transzoia and Tsavo areas on sloping rocky bushed grassland, 10-2400 m. It is usually confused with A. seyal Its non-powdery bark distinguish it from A. seyal var. seyal.

Gum resins Myrrh and frankincense are the main gum resins from Kenya’s drylands. These products are mainly processed for the extraction of essential oils. These oils are mostly used in aromatherapy, perfumery fragrance and flavour industries. Myrrh is used widely for medicinal purposes among many communities. It has been valued since Pharaonic times by the ancient Egyptians, who thought it essential for the proper preparation of mummies. Today it is highly valued in Islamic, Indian and Oriental medicine. Frankincense is used as incense and for religious ceremonies. Another important gum resin is Hagar from C. holtziana which is locally used to control ticks and mites.

Commiphora myrrha is the source of myrrh, the main Commiphora gum resin of economic importance locally known as mal mal in Somali. The tree is known as didin. This is a spiny shrub growing to 4m high with silvery or whitish to bluish grey peeling bark. The exudate is slightly scented, forming a hard translucent yellowish gum, the raw material of myrrh. The leaves are 1(-3)-foliolate, grey-green and very variable in shape and size, lateral leaflets, if present, usually much smaller than the middle one. It is found in Mandera and Wajir Districts usually growing on shallow soils over limestone or granite, rocky lava hills, in open Acacia-Commiphora bushland, between 220-800 m elevation with 230-300 mm rainfall.

9 It is highly valued in the two districts. Local names include Khumbi (Boran); Malmal, Molmol (Somali, the gum); Didin (Somali, the tree).

Gum resin

Commiphora myrrha Tree Stem Leaves

Commiphora holtziana (C. erythraea) is the source of the gum resin known as Hagar, used locally to control ticks. This is a tree to 6 m tall with a well-defined trunk. The outer bark white to yellowish, peeling in large papery flakes from the bluish-green under bark. The exudate is faintly scented, forms a gum resin locally known as Hagarsu by the Borana. The leaves are greyish green, 3-foliolate or occasionally 5-foliolate on long shoots. This is a widely distributed species of the drylands particularly in northern Kenya in Acacia-Commiphora bushland on well-drained red sandy soils, between 20-1100 m elevation with rainfall 220-630 mm. Common around Garba Tula. Local names include: Haggersu (Borana); Agarsu (Gabra); Haggr-ad (Somali).

Commiphora holtziana Tree Stem/Bark Leaves

10 Boswellia neglecta (B. hildebrandtii) is the source of frankincense, the main Boswellia gum resin of economic importance in Kenya. The resin is locally called Lobathin and it is also used as chewing gum. This is a much-branched shrub or tree to 6 m tall branching from very near the base from a short bole. Bark dark grey, not peeling and often with circular ridges or foldings. Leaves compound with 21-47 leaflets. Flowers white or greenish-white. Fruit green, often tinged with crimson, angled, opening when mature with the valves dropping and leaving a central winged column with the seeds attached. Boswellia neglecta is very common and occurs in most drylands in Acacia-Commiphora bushland particularly on red sandy soil over basement complex and on lava flows, between 200-1350 m elevation with 250-600 mm rainfall. Local names include: Dakhara, Hancha (Borana, Gabra), Kinodo (Kamba), Dakar (Orma), Lecholoo, Lkinoo (Samburu), Mathefur, Magafur (Somali).

Boswellia neglecta Tree Fruiting Branch Frankincense

Possible adulterants of commercial gums and gum resins Apart from Acacia senegal and A. seyal that produce gum arabic, Boswellia neglecta that produce frankinscence, and Commiphora myrrha, and C. holtziana with high value gum resins, there are a number of other indigenous trees that are also known to produce gums and gum-resin products that are similar but inferior and therefore of less commercial value. Their gums are possible adulterants particularly for gum arabic and myrrh.

Mixing gums from different species at collection time or at post-harvest handling stage results in variability and is the prime reason for poor quality resulting in low prices. Detection of adulterants requires familiarity with the genuine article. These species include: Acacia paolii Chiov. and A. mellifera (Vahl) Benth. in the family Mimosaceae for gum arabic and Commiphora africana (A. Rich.) Engl., C. confusa Vollesen, C.

11 habessinica (O. Berg) Engl., C. schimperi (O. Berg) Engl., C. pseudopaolii Gillett, C. kua (J.F. Royle) Vollesen var. gowllelo (Sprague) J.B. Gillett, and C. incisa Chiov. in the family for commercial gum resins.

Acacia paolii is a multi-stemmed, flat-topped shrub branching from the base, usually 2m high with white flowers and densely white hairy pods. It is found in most districts of northern Kenya, between 100-1250 m elevation but most common around Isiolo in the dry wooded grassland and bushland; often gregarious and dominant. It is known to hybridize with A. nubica. Local names include: Chachane, Wanga (Borana, Gabra, Orma); Gomor (Rendile); Gommor, Jerin, Jahjahneh (Somali); Eyelel, Elyuloit (Turkana).

Acacia mellifera is a multi-stemmed shrub easily distinguished by its larger leaflets (compared to other indigenous acacias) which are in 2 pairs only per pinna and its black hooked prickles arranged in pairs. This is a very common species in the drylands, at places forming almost pure stands on sandy soils and on lava, between 1-1800 m elevation. The species is locally called Sabansa-gurach (Borana); Muthiia (Kamba); Habalakes (Orma); Bilahen (Rendille); Iti (Samburu); Bil-el, Bilil, Lanen (Somali); Ebenyo (Turkana).

Commiphora africana is a much branched spiny shrub or tree up to 6 m tall with greyish to reddish-brown peeling bark. Leaves 3-foliolate. Flowers red, the exudate is milky, slightly scented, producing a hard gummy resin. This is a widespread species occurring in all the dryland areas. Local names include: Mbambara (Swahili); Ammes (Borana); Hammeesa (Gabra); Kitungu, Mutungu (Kamba); Chotwa (Marakwet); Komper (Orma); Lcheningiro (Samburu); Hammes sagara (Somali); Ekadeli (Turkana).

Commiphora confusa is a much-branched spiny shrub or small tree to 6 m tall with yellowish or brown outer bark peeling in papery flakes from the greenish under bark. The exudate is clear or milky, not scented. Leaves 3-foliolate. Flowers are yellow. This is a widely distributed species in the drylands occurring in most Acacia-Commiphora

12 bushland, between 150-1300 m elevation with rainfall of 300-700 mm. The species is often confused with C. africana and more so when they are growing together. Local names include: Hamesa, Tilchacho (Borana); Kilchacho (Orma); Hajola (Somali).

Commiphora habessinica is a spiny shrub or tree to 4 m tall with yellowish-grey outer bark, peeling from the pale green under bark in papery scroll or in massive white stripes. Leaves often 3-foliolate. The exudate is faintly scented, forming a gum resin. It is widely distributed in the drylands between 500-1900 m elevation with a rainfall of 300-800 mm. It is commonly found in Acacia-Commiphora bushland especially in rocky places and on lava hills. Local names include: Jalanga (Borana); Challankaa (Gabra); Mutungu, Mutungati (Kamba); Warabreb (Somali).

Commiphora schimperi is a spiny shrub or small tree to 6 m tall. Outer bark peeling in yellow grey or brownish curved flakes from the green under bark. The exudate is usually aromatic, producing a hard yellowish gum-resin. The leaves are 3-foliolate. Flowers greenish-yellow. It is a widely distributed species occurring in most districts in bushed grassland and Acacia-Commiphora bushland, between 430-1890 m elevation with rainfall 450-700 mm. Local names include: Masakaiya (Borana); Mutungu (Kamba); Lachimi (Samburu); Hargoi (Somali).

Commiphora pseudopaolii is a much-spreading spiny tree to 3 m tall, often wider than tall with the lower branches often lying on the ground. Outer bark white, peeling in large sheets from the blue-green under bark. The exudate is almost scentless, forming a gum resin. The leaves are normally 3-foliolate on long shoots. It is common in Garissa and Tana River Districts in the Acacia-Commiphora open bushland, often on alluvial soils, between 60-600 m elevation with 220-350 mm rainfall. The gum is also used locally against snakebite. Local names include: Hagersu (Borana); Hagharsu (Ilwana); Agar, Lailipai (Samburu); Hagarsu (Orma).

Commiphora kua var. gowlello is a spiny shrub or small tree to 3 m tall with long straggling branches and yellowish or silvery-grey peeling outer bark, peeling in

13 transverse strips. It has creamy exudate that is faintly scented, forming a hard yellowish gum resin. The leaves are usually 1-foliolate on short shoots but often 3-foliolate on the long ones. A common shrub of northern Kenya occurring in open bushland usually on sloping ground with red sandy soils, between 90-1000 m elevation with rainfall 230-300 mm. The gum is put into various medicinal uses and as substitute of myrrh. It is also used as soap. Local names include: Chalanga, Dabasso (Borana); Warab-reb (Somali).

Commiphora incisa is a spiny shrub up to 3 m high with yellowish outer bark, peeling transversely into scrolls. It has milky exudate that is faintly scented, hardening to a yellowish-red resin that has various medicinal uses. The leaves are generally 1-foliolate but sometimes 3-foliolate on the long shoots. This is a common shrub of northern Kenya in open Acacia-Commiphora bushland on sandy soils, between 60-1300 m elevation with 230-260 mm rainfall. Local names include: Waraa (Gabra); Warab-reb (Somali).

14 References

Beentje, H. 1994. Kenya Trees, Shrubs and Lianas. National Museums of Kenya, Nairobi. Brenan, J.P.M. 1953. Tropical African Plants: XXIII. Kew BULL. 8: 97-101, London. Brenan, J.P.M. 1959. Leguminosae, subfamily Mimosoideae. In Flora of Tropical East Africa (eds. Hubbard, C.E. & Milne-Redhead, E.), Crown Agents, London. Chikamai B.N. and Odera J.A. eds. 2002. Commercial Gums and Gum Resins in Kenya: Sources of Alternative Livelihood and Economic Development in the Drylands. Executive Printers, Nairobi, Kenya. Dharani, N. 2006. Field Guide to Acacias of East Africa. Struik Publishers (Adivision of New Holland Publishing () (Pty) Ltd). Cape Town. FAO, 1995b. Non-Wood Forest Products for Rural Income and Sustainable Forestry. FAO, Rome. FAO, 1998. Food and Nutrition Paper No. 52, FAO, Rome. Gachathi, F.N.M. 1994. Variation in Acacia senegal and its Relationship with Acacia circummaginata and Acacia thomasii in Kenya. Msc. Thesis in Pure and Applied Fungal Taxonomy, University of Reading, Reading. Ross, J.H. 1979. A conspectus of the African Acacia Species. Mem. Bot. Surv. S. Afr. No. 44: 55-58

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