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Novel, Universal Approach for the Measurement of Natural products in a Variety of Botanicals and Supplements
Botanicals contain a great diversity of compounds that exhibit wide variation in their physicochemical properties. Although no single analytical method is available to measure all potentially active components, HPLC with charged aerosol detection is a nearly universal approach that nonselectively measures any nonvolatile and many semivolatile compounds; that is, charged aerosol detection does not require that analytes be ionizable (as required for MS) or contain a chromophore (as required for UV). Furthermore, all non-volatile analytes produce similar response independent of chemical structure, enabling estimation of relative abundance when external standards are lacking.
A number of isocratic and gradient HPLC/UHPLC methods with charged aerosol detection were evaluated for the measurement of phytochemicals extracted from a variety of botanicals including: steroidal and pregnane glycosides from Hoodia gordonii; oxypregnane glycosides from Caralluma fimbriata; steroidal lactones from Withania somnifera; flavonolignans from milk thistle (Silybum marianum); triterpene glycosides from black cohosh (Cimicifuga racemosa); ginsenosides from ginseng (Panax ginseng); and diterpene glycosides from stevia (Stevia rebaudiana). Analytes showed consistent response (typically < 10% variability between compounds corrected for gradient elution). All methods had a wide dynamic range (˜four orders of magnitude), good sensitivity (typically low ng levels of detection), and excellent reproducibility (RSDs typically < 2%) even at low detection levels. Comparative data from ELSD and UV detection will also be discussed.