Characterization and Quantitation of Yohimbine and Its Analogs in Botanicals and Dietary Supplements Using LC/QTOF-MS and LC/QQQ-MS for Determination of the Presence of Bark Extract and Yohimbine Adulteration

Abstract

The compound yohimbine HCl has been restricted in Australia and categorized as a scheduled prescription drug in other parts of the world, including the United States where it is monographed as a drug in the U. S. Pharmacopeia. However, the bark of the yohimbe plant and its extract is considered a botanical that can be used as a dietary supplement in some parts of the world. For these reasons, methods to characterize the indole alkaloids of the bark and quantify yohimbine and its analogs are presented using accurate mass LC/quadrupole time-of-flight (QTOF)-MS and triple quadrupole LC/MS, respectively. Samples were extracted with a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method to characterize and quantify the indole alkaloids. With the LC/QTOF-MS in auto MS/MS mode the indole alkaloids were identified, and the isomeric response of each could be used to determine whether the actual bark or extract was in samples of dietary supplements and not adulteration with yohimbine HCl. Analogs were identified and include yohimbic acid, methyl yohimbine, and hydroxyl yohimbine. Many isomers of each were also detected, but identified only by the number of chromatographic peaks. Quantification of yohimbine and ajmalicine spiked extracts showed recoveries of 99 to 103% with RSD of 3.6% or lower and LODs of less than 100 ppt. Calibration of the two standards gave r(2) = 0.9999 in a range from 0.1 to 100 ppb. Dietary supplements quantified for these two compounds showed a range from not detected to 3x the amounts found in the bark.

Pharmaceutical quantities of yohimbine found in dietary supplements in the USA

“…Prior studies have also found yohimbine supplements to contain from 0% to 368% of the labeled quantity of yohimbine. [7][8][9] V. Raman and colleagues have previously analyzed the quality of 12 samples of commercial P. johimbe bark (i.e., material that is used by manufacturers to produce dietary supplements in contrast to the finished dietary supplement products analyzed in the current study) and they found that the quantity and quality of yohimbine were extremely variable. [5] In our current study, only 6.1% (3/49) of yohimbine supplement brands provided consumers with accurate information about the quantity of yohimbine contained in the supplement.…”

“…In the USA it is not legal to synthetically produce a compound, such as yohimbine HCl, and sell it in botanical supplements. [9,11] Recent studies, including the current study, have begun to explore how to accurately differentiate products that contain only yohimbine without associated stereoisomers and analogs which may suggest it has been adulterated with yohimbine HCl. [9] It is of much interest that, in our study, most supplements that did not contain either rauwolscine or corynanthine listed 'yohimbine HCl' on the label.…”

“…Other alkaloids, including corynanthine, rauwolscine (also known as α‐yohimbine), ajmalicine, and other yohimbine isomers, are also found in P . johimbe bark . Previously, capillary electrophoresis and gas chromatography–mass spectrometry have been used to analyze P .…”

“…[6,7] Other alkaloids, including corynanthine, rauwolscine (also known as α-yohimbine), ajmalicine, and other yohimbine isomers, are also found in P. johimbe bark. [8,9] Previously, capillary electrophoresis and gas chromatography-mass spectrometry have been used to analyze P. johimbe bark, but, more recently, high performance liquid chromatography (HPLC) coupled with photodiode and mass spectrometry detectors has been applied to the analysis of P. johimbe. [5,[7][8][9][10] P. johimbe extracts have traditionally been used as an aphrodisiac although, to our knowledge, there are no human clinical studies of P. johimbe extract for low libido or erectile dysfunction.…”

Assessment of the Authenticity of Herbal Dietary Supplements: Comparison of Chemical and DNA Barcoding Methods

“…For the quantification of yohimbine in yohimbe supplements, we used the chromatographic conditions described by Lucas et al [23], which provided satisfactory separation of yohimbine from other indole alkaloids in the samples. The injection of yohimbine standards at various concentrations provided an acceptable linear response in the range of 40 to 1060 µg/mL.…”