Identification and classification of Dendrobium candidum species by fingerprint technology with capillary electrophoresis

A capillary electrophoresis fingerprint method was established to evaluate the quality of Dendrobium candidum. The method of sample preparation and the electrophoresis condition were optimized to obtain highly sensitive and specific capillary electropherogram. The analysis was performed on a fused-silica capillary (65 cm × 75 µm i.d). The detection wavelength was 195 nm and a voltage of 20 kV was applied. The background electrolyte was a 40 mmol/L sodium borate solution (5% methanol, v/v) adjusted to pH 9.5 with 0.1 mmol/L NaOH solution. Medicinal materials were extracted by ethanol reflux for 2 h. The capillary electrophoresis fingerprints of 69-sample of Dendrobium candidum species from 10 different areas showed 15 characteristic peaks which could be applied to identification of this species. The coefficients were from 0.854 to 0.963 between standard fingerprint and each sample. The quantitative data of the fingerprints were analyzed by principal component analysis (PCO), UPGMA cluster analysis and the results showed that samples from different regions could be divided into three groups. Moreover, a rapid and convenient discriminant function was established to classify the Dendrobium candidum plants. The data revealed that the coincidence rate of all samples attached 100% by this discriminant model. The method is reliable and could be used to control the quality of medicinal plants including Dendrobium candidum species in the future.