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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.

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Cichoric acid is the main phenolic compound in the root and rhizome of the medicinal part, Echinacea purpurea that is known for possessing immune enhancing characteristics. In this study, we analysis the the synthesis and storage sites of phenolic compound in E. purpurea. We used fluorescent microscopy, transmission electron microscopy, cytochemical and immunocytochemical localization to observe the distribution of phenolic compounds. Our results show that the phenolic compounds were mostly distributed in the cortex parenchyma cells, vascular parenchyma cells and pith parenchyma cells in the root and rhizome, and mainly present in the vacuoles, large intercellular spaces and their surrounding cell walls. No phenolic compounds were observed in the cytoplasm and the organelles. We concluded that the phenolic compounds were synthetized in the cortex parenchyma cells, vascular parenchyma cells and pith parenchyma cells in the root and rhizome, and stored in the vacuoles of parenchyma cells. The above results provided significantly cytological information for further approaching the metabolic regulation and transfer pathways of phenolic compounds in biochemistry and molecular biology.

Quantitation of thin-layer chromatography (TLC) using image analysis is attractive for its low cost and convenience. The image analysis is investigated by designing a digital imaging system with simple equipment, developing an image analysis software based on our algorithm, and validated the system in the TLC quantitative assay of cichoric acid present in Echinacea purpurea (L.) Moench. TLC used a polyamide thin-layer plate with chloroform-methanol formic acid-water (3:6:1:1) as the mobile phase and 3% (m/v) aqueous aluminum chloride solution as the visualization reagent. Images are acquired with a standard digital camera under a UV viewing lamp (365 nm) in a dark room. The three-dimensional gray scale digital image dataset (x, y, gray) is reduced to two-dimensional dataset (distance, accumulative gray) and then plotted as a curve. The area under the peak corresponding to the cichoric acid spot is integrated and used for quantitation. The whole method was validated by the assay tests of detection limit, calibration curve, repeatability, reproducibility, and recovery. The results showed that our digital imaging method and image analysis algorithm were applicable for the quantification of TLC. The whole method is convenient, efficient, and moderately accurate for the quantitative assay of cichoric acid present in Echinacea purpurea (L.) Moench.

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