Compositional variation of atranorin‐related components of lichen Myelochroa leucotyliza dependent on extraction solvent and their quantitative analysis by qHNMR

Introduction Quantitative nuclear magnetic resonance (qNMR) is one of the effective and reliable quantification tools for natural product research. Myelochroa leucotyliza belongs to the genus Myelochroa, a common foliose lichen genus found in the Korean Peninsula, and has not been quantitatively ana...

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Published in:Phytochemical analysis 2021-11, Vol.32 (6), p.1067-1073
Main Authors: Ojha, Manju, Kil, Yun‐Seo, Youn, Ui Joung, Ok, Young Jun, Choi, Hyukjae, Nam, Joo‐Won
Format: Article
Language:English
Subjects:
Acetone
atranorin
Chloroform
Deuteration
Methanol
Myelochroa leucotyliza
Natural products
NMR
Nuclear magnetic resonance
qNMR
Quantitative analysis
Time dependence
Usnic acid
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Summary:Introduction Quantitative nuclear magnetic resonance (qNMR) is one of the effective and reliable quantification tools for natural product research. Myelochroa leucotyliza belongs to the genus Myelochroa, a common foliose lichen genus found in the Korean Peninsula, and has not been quantitatively analysed using NMR. Previous chemical studies on M. leucotyliza have been limited to the main components by traditional thin‐layer chromatography (TLC) experiments. Objective We explored the stability of atranorin, a major component of M. leucotyliza, in methanol and acetone using NMR and characterised the changes in the chemical profiles of the lichen extracts in methanol and acetone using qNMR. Methodology Atranorin transformation in the presence of methanol was analysed using time‐dependent proton (1H)‐NMR analysis (600 MHz NMR spectrometer). A 1H qNMR (qHNMR) method was established using dimethyl sulfone as the internal standard for quantifying the selected components isolated from M. leucotyliza. Homogenous mixtures of the samples were dissolved in deuterated chloroform. Results Time‐dependent 1H‐NMR experiments revealed that atranorin (5) from lichen M. leucotyliza decomposed into atraric acid (1) and methyl haemmatommate (2) in methanol. Four components were identified from M. leucotyliza: 1, 2, usnic acid (4), and 5, and their respective contents were determined using qHNMR. The percentages (w/w) of 1, 2, and 4 in the methanol extract were calculated as 5.66%, 0.69%, and 0.90%, while those of 1, 4, and 5 in the acetone extract were 1.70%, 1.68%, and 19.11%, respectively. Conclusion We used qHNMR to effectively analyse quantitative compositional variations in two different M. leucotyliza extracts and reliably determined the chemical conversion of the unstable compound atranorin. Myelochroa leucotyliza belongs to the genus Myelochroa, a common foliose lichen genus found in the Korean peninsula. In the present study, chemical investigation of M. leucotyliza was performed and the structures were identified as atraric acid (1), methyl haemmatommate (2), methyl chlorohaemmatommate (3), (+)‐usnic acid (4), atranorin (5), and (+)‐praesorediosic acid (6) by spectroscopic data analysis. The composition of 5 and its related components varied depending on the extraction solvent used, which was confirmed by quantitative NMR (qNMR) analysis.
ISSN:0958-0344
1099-1565
DOI:10.1002/pca.3048