Safrole, a phenylpropene with a ‘candy shop’ aroma, is abundant in nature among diverse plant genera such as Sassafras, Ocotea, Cinnamomum, Myristica, and Piper. Sassafras oil has been used extensively for a long time, first by Native Americans and later by European settlers in traditional medicine and as a flavouring agent. Until 1960 the consumption of safrole by the western population, as a flavouring agent in beer, meat, and soft drinks, was unregulated. Later, the recognition of this phytochemical as a weak hepatocarcinogen with demonstrated genotoxicity in rodents led to strict restrictions on its use in food by various regulatory bodies globally. Moreover, in Asian countries oral carcinogenesis has been linked to safrole through the habit of chewing betel quid. As a separate issue, safrole is an inexpensive synthetic precursor to the illicit recreational drug Ecstasy. Accelerating demand for this party drug during the last few decades has encouraged the unscientific harvesting, illegal production, and trading of safrole‐rich oils, leading to massive deforestation. Recently, many government authorities have enforced laws to restrict the production and harvesting of safrole‐bearing plants. Thus, the identity of safrole has altered with time from a pleasant flavouring agent to a hepatocarcinogen, and more recently as a driver of the destruction of biodiversity. Law enforcement has not only hampered its availability but has also extensively affected industrial use. Our review describes the research progress (1960–2018) on its natural distribution, carcinogenicity, usage as a natural synthon, and the regulations imposed on safrole and safrole‐rich oils worldwide. Finally, we draw our readers’ attention to the sustainable use of this phytochemical for a better future.
Introduction
Curcuma caesia (black turmeric), an essential oil‐bearing rhizomatous herb has been a part of ethnomedicinal practices in India and southeast Asian countries since ancient time. Oleochemical profile of black turmeric has been investigated previously by gas chromatography coupled to mass spectrometry (GC–MS) technique from different geographical regions showing a large variation in the identity as well as abundance of the constituents.
Objectives
To develop an analytical method for the reliable analysis of essential oil from black turmeric rhizome through identified chemical markers and to show the credibility of the developed method on real samples.
Methods
The essential oil of black turmeric was analysed through proton nuclear magnetic resonance (1H‐NMR) based method using an internal standard.
Results
Four thermolabile sesquiterpene markers were unambiguously identified from the essential oil of black turmeric rhizome. GC–MS based analysis produced an erroneous identification of the constituents. A standardised 1H‐NMR spectroscopy based method was developed for the qualitative and quantitative analysis of the identified chemical markers. The developed method was further utilised for analysing the variation in oleochemical profile across multiple batches of harvest and the rhizomes subjected to different post‐harvest storage or drying conditions.
Conclusion
The identified marker molecules and developed 1H ‐NMR spectroscopic method might prove to be a useful tool for the analysis of essential oil and quality control of this endangered crop material. Also, the present study provided information on the preferred drying and storage condition of black turmeric rhizome prior to the extraction of essential oil.
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