Thin-layer chromatographic identification of Chinese propolis using chemometric fingerprinting.
BACKGROUND
Poplar tree gum has a similar chemical composition and appearance to Chinese propolis (bee glue) and has been widely used as a counterfeit propolis because Chinese propolis is typically the poplar-type propolis, the chemical composition of which is determined mainly by the resin of poplar trees. The discrimination of Chinese propolis from poplar tree gum is a challenging task.


OBJECTIVE
To develop a rapid thin-layer chromatographic (TLC) identification method using chemometric fingerprinting to discriminate Chinese propolis from poplar tree gum.


METHODS
A new TLC method using a combination of ammonia and hydrogen peroxide vapours as the visualisation reagent was developed to characterise the chemical profile of Chinese propolis. Three separate people performed TLC on eight Chinese propolis samples and three poplar tree gum samples of varying origins. Five chemometric methods, including similarity analysis, hierarchical clustering, k-means clustering, neural network and support vector machine, were compared for use in classifying the samples based on their densitograms obtained from the TLC chromatograms via image analysis.


RESULTS
Hierarchical clustering, neural network and support vector machine analyses achieved a correct classification rate of 100% in classifying the samples. A strategy for TLC identification of Chinese propolis using chemometric fingerprinting was proposed and it provided accurate sample classification.


CONCLUSIONS
The study has shown that the TLC identification method using chemometric fingerprinting is a rapid, low-cost method for the discrimination of Chinese propolis from poplar tree gum and may be used for the quality control of Chinese propolis.
School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China, 510006.
Tie-xin
TX
Tang
Wei-yan
WY
Guo
Ye
Y
Xu
Si-ming
SM
Zhang
Xin-jun
XJ
Xu
Dong-mei
DM
Wang
Zhi-min
ZM
Zhao
Long-ping
LP
Zhu
De-po
DP
Yang
D000818:Animals; D001516:Bees; D002855:Chromatography, Thin Layer / Q000379:methods*; D016000:Cluster Analysis; D010449:Peptide Mapping; D032107:Populus / Q000737:chemistry*; D011429:Propolis / Q000737:chemistry / Q000302:isolation & purification*; D012116:Resins, Plant / Q000737:chemistry / Q000302:isolation & purification*; D014197:Trees
D012116:Resins, Plant; D011429:Propolis
Chinese propolis; chemometrics; fingerprinting; identification; image analysis; pattern recognition; thin-layer chromatography