African Sandalwood or Nepalese Sandalwood : a Brief Synthesis

African sandalwood or East African sandalwood (Osyris lanceolata Hochst. & Steud.; Santalaceae), also known as Nepalese sandalwood (Osyris wightiana var. rotundifolia P.C. Tam), is a hemi-parasitic tree known for its fragrant wood. The essential oil is extracted from the root bark for the perfume industry and different parts of the tree have various medicinal uses. African sandalwood contains an array of phytochemicals such as dihydro-β-agarofuran polyesters, agarofuranases, polyesters, other sesquiterpenes and bisabolanes. This mini-review focuses on the general biology, traditional uses, phytochemical properties, propagation for conservation, and hemiparasitism of O. lanceolata.

, which belongs to the Santalaceae, is most commonly known as East African sandalwood and Nepalese sandalwood.O. lanceolata is adopted, for uniformity, throughout this review and information from references of sandalwood with the above-listed synonyms are presented as O. lanceolata according to The Plant List (2016).
Osyris lanceolata is a shrub or small deciduous tree that grows to 1-7 m in height depending on the soil type, climatic conditions and genetic variation, and has a wide geographic distribution in Africa from Algeria to Ethiopia and south to South Africa, Europe (Iberian peninsula and Balearic Islands), Asia (India to China), and Socotra (von Breitenbach, 1963;Teklehaimanot et al., 2004;Giathi et al., 2011;Kamondo et al., 2012;Gathara et al., 2014;Global Plants, 2016).O. lanceolata is distributed in African countries such as Tanzania and Kenya and is frequently found in arid to semiarid areas, primarily on stony and rocky soils (Kokwaro, 2009), or sporadically in rocky sites and along the margins of dry forests, evergreen bushland, grassland, and thickets at an altitude range of 900-2250 m above sea level (Giathi et al., 2011;Kamondo et al., 2012).
However, large trees can occur in humid climates, preferentially in low soil pH andsufficient soil nitrogen (Mwang'ingo et al., 2003).O. lanceolata has yellow-green hermaphroditic flowers with small round heads, fruits are round, about 1 cm in diameter, green when unripe, orange to red when ripe, and contain one whitish seed (Mwang'ingo et al., 2008;Kamondo et al., 2012;Global Plants, 2016).Female flowers of plants growing in Spain flower for nearly six months from March to September while male flowers show almost year-round flowering (Herrera, 1984).Plant size exhibits dimorphism: males are significantly larger than females (Herrera, 1988a).Insects are not responsible for pollination and frugivorous birds are involved in seed dispersal (Herrera, 1985;Herrera, 1988b).O. lanceolata is a protected species under CITES appendix II (CITES, 2016).

Traditional uses
In East African countries, O. lanceolata constituted an important source of medicine but also has other minor uses such as fodder (Mwang'ingo et al., 2010).A decoction of the bark and root is considered to be useful for treating diarrhoea, gonorrhea, chronic mucus infections, and urinary diseases (Teklehaimanot et al., 2004;Kokwaro, 2009), a decoction of the bark in boiling water is used to treat candidiasis related fungal infections (Masevhe et al., 2015) while the essential oil extracted from the bark is used to treat diarrhoea, chest problems, and joint pains (William, 2010).In addition, O. lanceolata is used as an antimalarial in Kenya (Njoroge and Bussmann, 2006).Fibers from the roots are used in basket making while the strong red dye from the bark and roots is used in skin tanning (Mbuya et al., 1994).Since O. lanceolata is an evergreen tree with long flowering periods, it is a good forage plant (Fichtl and Adi, 1994).The utilization of O. lanceolata in the perfumery and fragrance industries (Ochanda, 2010) in the early 1900s followed a decline in the resource base of Indian sandalwood (Santalum album L.) (Rai and Sarma, 1990;Mbuya et al., 1994).Several communities in Kenya also use O. lanceolata to produce dyes, to treat various ailments, and to brew herbal tea (William, 2010;Kamondo et al., 2012).An infusion (250 ml) consisting of a handful of roots cooked in water for 5 min or pounded with warm water, is administered three times a day to treat diarrhoea (Semenya and Maroyi, 2012).In South Africa, roots are traditionally used to treat menorrhagia (Arnold and Gulumian, 1984;Steenkamp, 2003).The antimicrobial activity of hexane, dichloromethane, aqueous methanol and water extracts from the stem, roots and stem bark was shown by Ooko (2008) against five bacteria and three fungal strains.Roots and leaves have antifungal and antibacterial activities (Mulaudzi et al., 2011).A large population of the residents (64%) of Chyulu hills in Eastern Kenya use O. lanceolata for commercial purposes and 21.2% use the tree for medicinal purposes to treat animals and humans, e.g. to treat snake bites (Ochanda, 2010).An extract from shoots is used as an antipyretic agent for cattle (Thanner, 1908).The root bark is used to treat indigestion (Manandhar, 1993) and to cure body pain and bone fractures in Nepal (Gautam, 2013).A leaf extract, when mixed with cow's butter or Indian rape oil (Brassica napus L. var.napus) forms an ointment used to treat sprains (Bhattarai, 1990).Young leaves are poisonous to livestock (Shrestha and 58 Dhillion, 2003), but when boiled, dried and powdered, they are used as herbal tea (Shrestha, 1988;Paudel and Gyawali, 2014).This tea also acts as a labour-inducing agent to treat fractured bones (Paudel and Gyawali, 2014).The methanolic extract of leaves can inhibit the growth of Pseudomonas aeruginosa, Proteus mirabillis, Salmonella typhi and S. paratyphi (Paudel and Gyawali, 2014).The leaf extract induced weight loss in mice and serves as an effective parasitemic agent (Girma et al., 2015).The methanolic extract of aerial parts during the fruiting period is rich in flavonoids and effectively reduces inflammation (Gómez et al., 1995).

Propagation and conservation
O. lanceolata products in the international markets in Europe and Asia have increased in demand, recently leading to an increased rate of utilization and exploitation, to an extent that its survival in natural habitats is severely threatened (William, 2010).The traditional mode of propagation is by seed or root suckers (Kokwaro, 2009).Propagation by seeds is difficult due to a limited supply and availability of seed at the right time (being a dioecious species, the spatial distribution of trees affects the reproductive outcome; Mwang'ingo et al., 2008), storage difficulties and thus poor germination (Mbuya et al., 1994).Consequently, several interventional measures are required to conserve O. lanceolata.A study by Mwang'ingo et al. (2004) on the storage and pre-sowing treatments on seed germination demonstrated that the testa covering the embryo plays a significant role in limiting germination by restricting gas and water entry and also acts as a mechanical barrier to embryo growth.However, complete removal of the testa and soaking the zygotic embryo in hot water enhanced seed germination by 66.5%, shortened the time to seedling emergence and promoted early seedling growth (Mwang'ingo et al., 2004).Stem cuttings (8-10 cm long with 3-4 leaves from young trees or seedlings) could be induced to root with a maximum of 15% rooting when dipped first in a fungicide (Bavistin) for 5 min, then in 1% indole-3-butyric acid (IBA) for 6 h, but "this concentration could be increased to 32.5% when 75% of the original leaves were left intact" (Giathi et al., 2011).In the same study (Giathi et al., 2011), the choice of substrate was shown to affect the rooting ability of cuttings, with 30% of cuttings rooting in vermiculite, which was superior to sand, vermiculite + sand (1:1), activated coconut peat and peat.Teklehaimanot et al. (2004) used 50-150 mg/L IBA to enhance root production in young stem cuttings collected in early spring.Mwang'ingo et al. (2006) initiated air layers that were left on parent trees for eight weeks and watered every two days to allow root initiation with the help of three concentrations (50, 100 and 150 mg/L) of IBA during February, June, September, and December: 50 mg/L IBA was optimum for root initiation and June to September was best for air layering with about 80% rooting success after potting plants in sand, forest soil and animal manure (2:1:1) and fertilizing with 5 g/container of NPK (nitrogen: phosphorus, potassium) fertilizer.Machua et al. (2008) achieved 60% rooting success through air layering.

Future perspectives
Tissue culture serves as one potential means of propagating and conserving O. lanceolata by drawing from experience on S. album (Kalabamu Xavery and Feyissa, 2015;Teixeira da Silva et al., 2016).Molecular markers can differentiate adulterants and distinguish among different sandalwood extracts (Bhat et al., 2006).Plants can accumulate heavy metals (Pb, Cu, and Zn) (Liu et al., 2008), suggesting that African sandalwood could be explored for phytoextraction or phytoremediation.