IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

1.6.4 Analysis
SOME TRADITIONAL HERBAL MEDICINES 81
A procedure based on an extraction method used in Germany for the determination
of aristolochic acids in botanical products has been developed and applied to a variety of
botanicals and botanical-containing dietary supplements. Aristolochic acids are extracted
from the sample matrix with aqueous methanol/formic acid. The concentration of aristolochic
acids in the extract is determined by gradient high-performance liquid chromatography
(HPLC) with UV absorption detection at 390 nm and their identity is confirmed
by liquid chromatography/mass spectrometry using either an ion-trap mass spectrometer
or a triple quadrupole mass spectrometer. The quantitation limit is equivalent to 1.7 μg/g
in solid samples and 0.14 μg/mL in liquid samples (Flurer et al., 2000).
Lee et al. (2001) developed an HPLC procedure with a silica gel RP-18 reversedphase
column to determine aristolochic acids I and II in medicinal plants and slimming
products. The recovery of these two compounds in medicinal plants and slimming
products by extracting with methanol and purifying through a PHP-LH-20 (piperidinohydroxypropyl
Sephadex LH-20) column was better than 90%.
Targeted liquid chromatography/serial mass spectrometry (LC/MS/MS) analysis,
using a quadrupole ion-trap mass spectrometer, permitted the detection of aristolochic
acids I and II in crude 70% methanol extracts of multi-component herbal remedies
without any clean-up or concentration stages. The best ionization characteristics were
obtained using atmospheric pressure chemical ionization (APCI) and by including
ammonium ions in the mobile phase. Limits of detection for aristolochic acids were
influenced by the level of interference due to other components in the sample matrix.
They were determined to be between 250 pg and 2.5 ng on-column within a matrix containing
compounds extracted from 2 mg of herbal remedy (Kite et al., 2002).
Ong and Woo (2001) developed a method for the analysis of aristolochic acids in
medicinal plants or Chinese prepared medicines using capillary zone electrophoresis
(CZE). The limits of detection for aristolochic acids I and II were 30 and 22.5 mg/kg,
respectively. The proposed method using pressurized liquid extraction with CZE was
used to determine the amount of aristolochic acids in medicinal plants or samples of
Chinese prepared medicines with complex matrix and the results were compared with
those from HPLC. Results obtained for aristolochic acids I and II in medicinal plants by
CZE and HPLC are presented in Table 1.
Ong et al. (2000) compared extraction and analysis of aristolochic acids I and II in
medicinal plants (Radix aristolochiae) using a pressurized liquid extraction method in a
dynamic mode with ultrasonic and Soxhlet extraction. The effects of temperature,
volume of solvent required and particle size were investigated. The pressurized liquid
extraction method showed some advantages over ultrasonic and Soxhlet extraction
methods.
Singh et al. (2001a,b) developed a reversed-phase HPLC method with photodiode
array detection for quantitative detection of aristolochic acids in Aristolochia plant
samples. The procedure involves extraction of aristolochic acids with methanol and