Saving the East Indian sandalwood tree

Santalum album Plant cell cul­tures have yiel­ded valu­able nat­ural products in the form of phar­ma­ceut­ic­als, fla­vours and fra­grances, and agri­cul­tural, cos­metic, bio­herb­i­cidal and fine chem­ic­als, with approx­im­ately 2000 new plant chem­ic­als added annu­ally. The global mar­ket for plant-derived drugs was worth an estim­ated US$18 bil­lion in 2005, with an expec­ted annual growth rate of 6.6% to US$26 bil­lion by 2011.

The East Indian san­dal­wood tree, Santalum album, is a woody and trop­ical forest tree that belongs to the fam­ily Santalaceae. The spe­cies is glob­ally acclaimed for its very costly heart­wood and essen­tial oil obtained from matured spe­ci­men trees. Unmet needs for use in per­fumery (fra­grance) and as food addit­ives (fla­vour) have led to the decline of nat­ural san­dal­wood pop­u­la­tions due to illegal trade and har­vest­ing and over­ex­ploit­a­tion. The estim­ated global annual require­ment is ∼10,000 tons of wood (equi­val­ent to 200 tons of oil), involving a trade of approx­im­ately US$125 mil­lion, of which only 10% is met from nat­ural resources. A nat­ural enemy in the form of the myco­plas­mal ‘spike dis­ease’ has placed the spe­cies on the IUCN Red List of Threatened Species.

Sandalwood also has extens­ive applic­a­tions in tra­di­tional medi­cinal sys­tems such as Ayurveda, and is gain­ing increas­ing import­ance in mod­ern phar­ma­co­lo­gical invest­ig­a­tions as a pos­sible source of anti­c­an­cer, anti-Helicobacter pylori and anti­viral bio­molecules. However, the havoc caused by the epi­demic spike dis­ease and the hemi-parasitic and slow-growing nature of the tree neces­sit­ated research towards the devel­op­ment of bio­tech­no­lo­gical means of in vitro pro­duc­tion as early as 1963. A recent paper in AoB PLANTS describes a bioreactor-based pro­duc­tion sys­tem as a bio­tech­no­lo­gical means of propaga­tion for this endangered species.


Culture of East Indian san­dal­wood tree somatic embryos in air-lift biore­act­ors for pro­duc­tion of san­talols, phen­olics and ara­binogalactan pro­teins. (2013) AoB PLANTS 5: plt025 doi: 10.1093/aobpla/plt025
The East Indian san­dal­wood tree, Santalum album, yields one of the cost­li­est heart­woods and pre­cious essen­tial oil. Unsurprisingly, this endangered forest spe­cies is severely affected due to unmet global demands, illegal trade and har­vest­ing, over­har­vest­ing and an epi­demic myco­plas­mal spike dis­ease. In vitro micro­p­ropaga­tion endeav­ours have res­ul­ted in defined in vitro stages such as somatic embryos that are amen­able to mass pro­duc­tion in biore­act­ors. We report on somatic embryo pro­duc­tion in a 10-L air-lift-type biore­actor, and com­pare the growth and bio­chem­ical para­met­ers with those of a 2-L air-lift-type biore­actor. For the 10-L biore­actor with bio­mass (475.7 ± 18 g fresh weight; P < 0.01), con­com­it­antly san­talols (5.2 ± 0.15 mg L−1; P < 0.05), phen­olics (31 ± 1.6 mg L−1) and ara­binogalactan pro­teins (AGPs) (39 ± 3.1 mg L−1; P < 0.05) are pro­duced in 28 days. In addi­tion, we iden­ti­fied and quan­ti­fied sev­eral san­talols and phen­olics by means of high-performance thin-layer chro­ma­to­graphy and reverse-phase high-pressure liquid chro­ma­to­graphy ana­lyses, respect­ively. Results indic­ate that 10-L-capacity air-lift biore­act­ors are cap­able of sup­port­ing somatic embryo cul­tures, while the extra­cel­lu­lar medium provides oppor­tun­it­ies for pro­duc­tion of indus­trial raw mater­i­als such as san­talols, phen­olics and AGPs. This will prove use­ful for fur­ther optim­iz­a­tion and scale-up stud­ies of plant-produced metabolites.


AJ Cann. ORCID 0000-0002-9014-3720

Alan Cann is a Senior Lecturer in the School of Biological Sciences at the University of Leicester and formerly Internet Consulting Editor for AoB.