Rapid identification of Digitalis purpurea using near-infrared reflectance spectroscopy

Glycosides from Digitalis are widely used for the treatment of various cardiac conditions. The potential for near-infrared (NIR) spectroscopy as a technique for the rapid identification of Digitalis purpurea was studied. If successful, this method would be advantageous over traditional methods which are destructive and time-consuming. It was possible to identify D. purpurea from other plants using a Maximum Distance in Wavelength Space statistical comparison method on standard normal variate-corrected, second-derivative spectra. Match values ranged from 1.65 to 2.26 for correct identification and were greater than 11.2 [corrected] for other plants. It was also possible to discriminate between different plant parts of D. purpurea, with match values ranging from 1.52 to 2-26 for leaves and greater than 29 for other parts of the same plant. The use of correlation coefficients and the Correlation in Wavelength Space methods proved less conclusive, with resulting values for leaves from different plants being very high, and in all but one case, above 0.9. A two-wavelength, nearest neighbours analysis was carried out for de-trended (baseline corrected), standard normal variate-corrected spectra at 1150 and 2160 nm. This resulted in the successful identification of unknown samples. NIR spectroscopy has the potential for the rapid identification of D. purpurea, and possibly for other natural products of pharmaceutical interest.