Sandalwood oil, particularly East Indian sandalwood (Santalum album), holds a special place in the perfumery industry due to its exquisite fragrance and therapeutic properties. With a history of use spanning over 4000 years, East Indian sandalwood is one of the oldest known perfume materials and has gained popularity in American and European perfume industries over the last century.
However, its popularity has given rise to a concerning issue - the adulteration and mixing of sandalwood oil with various other substances.
The Complexity of Identifying Sandalwood Species
Across the globe, more than 15 distinct species of sandalwood can be found. Among these, some produce a remarkably aromatic wood known as heartwood, which maintains its delightful fragrance for several decades.
In the sandalwood industry, two main species are used commercially: East Indian sandalwood (S. album) and Australian sandalwood (S. spicatum).
S. album is primarily distributed in the states of Karnataka and Tamil Nadu on the Deccan Plateau in India, as well as in Marayoor on the eastern side of the Western Ghats in Kerala. This fragrant wood is highly prized, and its oil finds use in incense, soaps, creams, perfume, and fine carving.
Alternatively, S spicatum, despite containing fewer alpha and beta santalols, is still considered a high quality sandalwood oil.
Forms of Adulteration
The problem starts when either one of these expensive oils is adulterated with either natural or chemical diluents, or when other, inferior sandalwood species like the Osyris lanceolata plant, commonly known as African sandalwood, are used instead of the real sandalwood oil. Both species share physical and wood anatomical similarities, making visual identification challenging, especially when they are being traded in small chips or powder forms. However, the high santalol content in Indian sandalwood and specific differences in rDNA sequences offer valuable features for distinguishing between the two species.
Diluents being used commonly are Amyris (amyris balsamifera), Atlas cedarwood (Cedrus atlantica), Castor oil, and Copaiba (Copaifera). They are often blended with sandalwood oil. Additionally, the oil may be diluted with triacetin, benzyl benzoate, and synthetic sandalwood substitutes derived from alpha campholenic aldehyde. This adulteration compromises the purity and authenticity of the oil, leading to confusion among consumers seeking genuine products for their aromatherapy and cosmetic needs.
How to Test for Authenticity and Purity?
While distinguishing the actual wood of African Sandalwood (Osyris Lanceolata) from Indian or Australian Sandalwood can be done relatively easy with a microscope (1) it is more difficult with their oils. For added components involving synthetic compounds or components extracted from more affordable essential oils routine GC-MS testing is hardly enough. However, more cutting-edge technology such as HPLC, fast GC, GC x GC, IRMS, MS, and 1H, 13C NMR testing is being used successfully. (2)
Is Genetically Modified Sandalwood Coming?
Another factor to keep in mind is that genome sequencing hase shed light on the potential transformation of sandalwood through gene(s) resistant to various diseases, as well as possibilities for metabolic engineering to increase or modify essential oil yield. This has potential economic importance in the preparation of perfumes, cosmetics and other applications. Lets keep in mind though that such developments, as we also have seen happening in the food industry with wheat, sugar beet, soy crop and others, is not entirely without problem. In countries in which GMO wheat for example is legally sold as groceries, here is an unequal increase of gluten sensitivity, a disease that was unknown some twenty years ago.
Who is to say that such development in the essential oil industry is not going to lead to similar challenges.
Addressing the challenge of identifying authentic sandalwood species, being able to successfully test for natural as well as synthetic adulterations is vital to preserving the integrity of the essential oil industry and ensuring consumers can confidently choose pure and genuine sandalwood products for their aromatic and their therapeutic needs.
Sources:
(1) Identification of Santalum album and Osyris lanceolata through morphological and biochemical characteristics and molecular markers to check adulteration (Final Report of the project KFRI 509/06) K. V. Bhat Forest Utilization Division M. Balasundaran SNPFM Divison M. Balagopalan Instrumentation Division
(2) Adulteration of Essential Oils and Detection Techniques by Dr. Sudhir Mestri. Link: https://www.linkedin.com/pulse/adulteration-essential-oils-detection-techniques-dr-sudhir-mestri/