Chemometrics gets to the root of TCM UHPLC data

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  • Published: Jan 1, 2018
  • Author: Ryan De Vooght-Johnson
  • Channels: Laboratory Informatics / Chemometrics & Informatics
thumbnail image: Chemometrics gets to the root of TCM UHPLC data

New methods needed for morinda root analysis

Morinda root (ba ji tian) is the root from the vine-like shrub Morinda officinalis. It is used extensively in traditional Chinese medicine to boost the immune system and to treat menstrual disorders, impotence, kidney disorders and inflammatory diseases, such as rheumatoid arthritis. There are a number of compounds in the root that are believed to be active, such as various anthraquinones and iridoid glycosides. However, there is at present no analytical method that gives an unambiguous indication of the overall bioactivity of morinda root samples since current methods only look at one or two compounds.

The Beijing and Haikou researchers developed a new method that uses UHPLC to assay 11 different bioactive compounds. Since they had UV maxima at different wavelengths, DAD (PDA) was employed for detection. Various chemometric techniques were used to classify 25 samples from four provinces of China: Hainan, Guangdong, Guangxi and Fujian.

UHPLC and chemometrics used to analyse ba ji tian

Ground root samples were extracted with refluxing methanol for 1 hour. The extraction conditions were carefully optimised, showing that longer reflux times gave no increase in yield. The extracts were filtered and evaporated; the residues were then taken up in 5 mL of methanol and membrane filtered prior to UHPLC analysis.

UHPLC employed a Waters Acquity UPLC H-Class system fitted with a Waters XBridge BEH C18 column, which proved to give better separation than other columns. Aqueous formic acid (0.3%) and acetonitrile were used as mobile phases, the proportion of the latter being raised from 7 to 90% in a series of gradients. The DAD was monitored at 254 nm for the iridoid glycosides and 277 nm for the anthraquinones. Reference standards of the 11 compounds were used to identify and quantify the peaks. The method was successfully validated, being shown to be accurate and precise.

Hierarchical cluster analysis (HCA) was applied to the UHPLC results from the 25 samples, separating them into two main clusters, one of which contained the two samples from Hainan province, while the other contained the remaining 23 samples. Further division of the latter cluster into two sub-clusters was possible, but these did not correspond to geographical origin.

Principal component analysis (PCA) was applied to the data. A two-component model separated the two Hainan samples from the other 23, but did not clearly further divide the latter group. Partial least-squares discriminant analysis (PLS-DA) was also applied, separating the data into three groups on a PLS-DA score plot. One group contained the two samples from Hainan province, while the other two more or less corresponded to the two sub-clusters seen in the HCA.

UHPLC and chemometrics help to determine origin of morinda root samples

The new UHPLC method gives a useful overall picture of the active compounds in morinda root and is suitable for routine analysis. The chemometric methods could distinguish samples from the island of Hainan from those from the three mainland provinces, but could not distinguish between the latter. It is possible that the different climate of Hainan affects the composition of the root, or genetic factors may be responsible for the variation in composition. It would be useful to repeat this work with a greater number of samples to see whether the results remain the same.

Related Links

Journal of Separation Science, 2017, 40, 3996-4003. Zhao et al. Evaluation and quantitative analysis of 11 compounds in Morinda officinalis using ultra-high performance liquid chromatography and photodiode array detection coupled with chemometrics.

Wikipedia, Hierarchical Clustering

Wikipedia, Partial least squares regression

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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