Identification of Dendrobiums in situ by Raman spectroscopy and micro-computed tomography imaging

Abstract

Background Dendrobium candidum/officinale (Dendrobium candidum Wall.ex Lindl.; Dendrobium officinale Kimura et Migo) is an expensive medicinal plant used mainly as a tonic in China. Tie-pi-feng-dou is the common name of the processed medicinal Dendrobium candidum/officinale. The market prices of Dendrobium sources vary significantly and it is difficult to identify different types of Dendrobiums due to their similar appearances. The use of counterfeit Dendrobium candidum/officinale is ubiquitous and problematic. Therefore, it is important to be able to discriminate between the wide range of available Dendrobium. Methods In an effort to better distinguish between the varieties of Dendrobium, Raman spectroscopy was used to detect specific Dendrobiums relative to their source. Transport channel imaging of the microstructural sites by micro-computed tomography (micro-CT) was used to identify the unique constitution and enrichment status of dendrobines, which was determined mainly by the geographical source of the Dendrobium. This implies that exclusive spectral traits may be unique to different regions. The presence or absence of these traits differ among the geographical origins. Results We can identify several spectral traits for various Dendrobiums. An intense peak at 1,525 cm−1 was only found in Dendrobium candidum/officinale (Zhe-jiang/Yun-nan/An-hui), while the characteristic Dendrobium candidum/officinale bands were near 742 cm−1, 1,326 cm−1 and 1,330 cm−1. A systematic method for distinguishing between four geographical locations of Dendrobium (Zhe-jiang/Yun-nan/An-hui/Gui-zhou) were established. This reveals that the origin of an unknown Dendrobium may be identified by Raman spectroscopy and micro-CT imaging. This method was shown to be efficacious, fast, and non-destructive.