UPLC-MS profiling, identification of major peaks and comparison of Harpagophytum procumbens extracts from different locations

Abstract

Organic extracts (methanol:acetonitrile (1:1 v/v)) of the dried and grounded secondary tubers of Devil's Claw, Harpagophytum procumbens (Burch.) DC. ex Meisn., produced extracts rich in iridoid glucosides. An UPLC-MS profiling method was developed that could separate the major compounds found in the extracts and allowed for high resolution mass spectral evaluation of the compounds detected. By using reference standards, the presence of six compounds could be confirmed namely harpagide, verbascoside, isoverbascoside, harpagoside and 6-acetylacteoside. The high mass accuracy of the TOF data also allowed for the tentative identification of three compounds, namely dihydrichinatrienone, totaratrienediol and a possible isomer of 6-acetylacteoside based on the observed accurate mass and fragmentation pattern. By using the extracted mass chromatogram of the known compounds of H. procumbens, a rapid assessment of the identity of the plant extract can be made. A statistical evaluation of H. procumbens plant material obtained from two different sources using Scores Plot indicated similarity as well as differences between the CSIR and PlantLIBRA samples. A further evaluation of the data via a Hotellings T2 Range comparison indicated that the two samples were > 95% similar, while the Scores Plot data revealed that the indicated differences were caused by concentration variations between the CSIR and PlantLIBRA sample. The developed analytical method was applied to the comparison of 12 PlantLIBRA samples and a CSIR sample. The method was found suitable for profiling H. procumbens extracts and can also be used to manually or statistically evaluate samples for similarities/differences. It would thus be suitable to screen for batch to batch reproducibility of crude plant material as well as processed samples.