Objective

2

The volatile components of Rhododendri Mollis Flos were determined and the differences of volatile components at different flowering stages were compared and analyzed.

Method

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Gas chromatography-ion mobility spectrometry （GC-IMS） was used to detect the volatile components in Rhododendri Mollis Flos at different flowering stages （bud stage， initial flowering stage， half-flowering stage， blooming stage and late blooming stage）. GC-IMS spectra combined with cluster analysis， principal component analysis （PCA） and orthogonal partial least squares-discriminant analysis （OPLS-DA） were used to compare the differences and similarities of volatile components in different flowering stages.

Result

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A total of 70 volatile components in Rhododendri Mollis Flos at different flowering stages were detected， among which 67 were common components， and 47 were identified qualitatively， mainly alcohols， esters and aldehydes. Carveol was a special component at the late blooming stage. The content of alpha-terpineol is the highest at the initial flowering stage， but not at the blooming stage and late blooming stage. The relative contents of the active ingredients ［6-methyl-5-hepten-2-one， nonanal， alpha-terpineol， 1，8-cineole， linalool oxide， 1-octen-3-ol， （

E

）-3-hexenol］ showed a decreasing trend during flowering stages. GC-IMS spectra showed that the samples at different flowering stages had their own characteristic peak regions， and also had common regions. The results of cluster analysis， PCA and OPLS-DA all showed that the samples at different flowering stages were distinguishable. OPLS-DA was used to screen 19 different components to distinguish different flowering stages， including

γ

-butyrolactone， 1，8-cineole， ethyl hexanoate， etc.

Conclusion

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Rhododendri Mollis Flos samples at different flowering stages can be distinguished obviously， and the active substances in the volatile components are gradually dissipated with the degree of flower opening， which can provide reference for the improvement of material basis and the study of different flowering stages of Rhododendri Mollis Flos.