I hate to do this, but when you see misinformation on the net, and you write to website owners several times to ask them to put it right, and they don’t respond, you have no choice.
The African Laboratory for Natural Products website looks like an excellent project, and analytical data on African essential oils is presented at http://www.ics.trieste.it/EssentialOils/EssentialOils.aspx Unfortunately some of the data sources used have been criticised/discredited long ago, and some presented analyses uniquely break new territory in discovered components. Or are just plain wrong.
For example the entry for Sandalwood Oil (Santalum album) is pretty sparse and in any case it news to me that it grows naturally in Africa – African sandalwood oils are usually designated as Osyris spp. The limited data on composition is quite unsafe: 2.5% beta-ionone (this material does not occur in genuine sandalwood oil) and 90% santalols is given, quoting Masada (1976) as a reference. In fact the book written by Masada: Analysis of Essential Oils by Gas Chromatography and Mass Spectrometry has been widely criticised, many workers claiming that Masada was analysing adulterated oils - I suppose this is better than saying he mistakenly identified many of the components. To be fair to Masada, the reference to Sandalwood oil East India (pp 223-225) refers sp[ecifically to the wet chemical method of santalol estimation outlined in old BPC and FCC specs. We now know, thanks to the direction of Verghese et al. (1990) that the improved accuracy of high performance capillary GC indicates lower values, Verghese stating that the normal range for alpha-santalol is in fact typically 40-45% and for beta-santalol from 17-27%. The website entry doesn’t reflect this information.
Under Jasmin “oil” from Jasminum officinale we have similar misquotes from Masada, who in fact analysed Turkish Jasmin absolute (p80-81), not the “oil” as stated, quite an important difference. Masada quoted compositions of 70-80% of benzyl acetate, approx 7.5% of linalyl acetate and 15-20% of linalol amongst others, in analytical data for jasmine absolute composition. More recently, in a study of Turkish jasmin absolutes from Antalya, Anac (1986) showed that in fact higher paraffins account for the major portion of Turkish jasmin absolutes, with phytol isomers also making a large contribution. By more accurately accounting for the higher boiling components, the benzyl acetate content was found to be reduced to an average of 16.77%. Interestingly, Anac failed to find linalyl acetate in any of the samples analysed.
The tea tree oil (Melaleuca alternifolia) data from Zimbabwe is interesting. It is not clear whether this is an alpha-terpinene chemotype, or a terpinolene chemotype (“alpha-terpinolene” as quoted on the site is not a recognisable hydrocarbon to this author, and is presumably a mis-spelling). The low terpinen-4-ol content, quoted at 7%, makes the oil commercially uninteresting.
The analysis of Geranium oil (P. graveolens) from a plant in the ANLAP garden is weird. Citronellal (7.2%) and thymol (4.6%) are not normally associated with geranium oils. Weirder still is the presence of citronellal (6.6%) estragole (3.6%), cinnamaldehyde (4.5%) and citronellyl formate (2.3%), in Rosemary oil (Rosmarinus officinalis) from Rosemary sourced from an Addis Ababa market. In fact I have a very hard time believing it.
References:
Anac O. (1986) “Gas Chromatographic Analysis of Absolutes and Volatile Oil
Isolated from Turkish and Foreign Jasmin Concretes” Food & Frag. J. 1,
115-119.
Masada Y. (1976) Analysis of Essential Oils by Gas Chromatography and Mass Spectrometry John Wiley NY 1976.
Verghese J. et al. (1990) Flavours & Fragrances J. 5, 223-226.
Copyright © June 2005 by Tony Burfield. All Rights Reserved.