A ¹H‐NMR spectroscopic method for the analysis of thermolabile chemical markers from the essential oil of black turmeric (Curcuma caesia) rhizome: application in post‐harvest analysis

Abstract

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.

Essential Oils as Multicomponent Mixtures and Their Potential for Human Health and Well-Being

“…(Zingiberaceae) rhizome (Fakhari et al, 2005;Turek and Stintzing, 2011;Mahanta et al, 2020;Truzzi et al, 2021). According to Bakkali et al (2008), about 3,000 EOs are known to date from a wide variety of plants and their organs, of which 300-400 are particularly important in the medicinal, pharmaceutical, agricultural, food, sanitary, cosmetics and perfume industries, as well as in dentistry, as adhesives and flavors (Ramezani et al, 2008;Turek and Stintzing, 2013;Ibrahim, 2020).…”

“…In addition, analytical techniques such as nuclear magnetic resonance (NMR) spectroscopy and headspace gas chromatography play a role in characterizing and evaluating EOs quality and authenticity, especially for unstable EO molecules like thermolabile sesquiterpenes, such as from Curcuma caesia Roxb. (Zingiberaceae) rhizome ( Fakhari et al, 2005 ; Turek and Stintzing, 2011 ; Mahanta et al, 2020 ; Truzzi et al, 2021 ). According to Bakkali et al (2008) , about 3,000 EOs are known to date from a wide variety of plants and their organs, of which 300–400 are particularly important in the medicinal, pharmaceutical, agricultural, food, sanitary, cosmetics and perfume industries, as well as in dentistry, as adhesives and flavors ( Ramezani et al, 2008 ; Turek and Stintzing, 2013 ; Ibrahim, 2020 ).…”

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“…A study conducted by Mahanta BP et al, 48 on Curcuma caesia, commonly known as black turmeric belonging to the family Zingiberaceae, traditionally its rhizomes have been utilized for leprosy, asthma, bronchitis, epilepsy, piles, etc. Results of earlier studies on black turmeric by GC-MS were found to have large variations of phytoconstituents present.…”

Quantitative Determination of Acrolein in Cider by 1H NMR Spectrometry

“…In addition, it is soluble in water and produces a strong and clear singlet signal, which never overlaps with any other signal of the ciders. The use of internal standards in quantitative 1 H NMR is a common procedure used in many determination methods [26][27][28][29][30]. TSP ((CH 3 ) 3 -Si-CD 2 -CD 2 -COONa) was soluble in water and had a simple 1 H NMR spectrum with a single nine proton singlet, corresponding the three methyl groups -CH 3 .…”