p-Hydroxybenzoic acid alkyl esters in Andrographis paniculata herbs, commercial extracts, and formulated products.
Analysis of two commercial extracts of Andrographis paniculata using high-performance liquid chromatography (HPLC) with photodiode array absorbance detection showed the presence of several unexpected compounds, which were isolated and identified as methyl, ethyl, and propyl esters of p-hydroxybenzoic acid by using high-resolution mass spectrometry and nuclear magnetic resonance. Quantitative analysis using HPLC revealed the presence of 0.22% p-hydroxybenzoic acid methyl ester (methlyparaben) in one commercial extract, and both 0.11% p-hydroxybenzoic acid ethyl ester (ethylparaben) and 0.20% p-hydroxybenzoic acid propyl ester (propylparaben) in a second commercial extract of A. paniculata. Analyses of additional commercial products of A. paniculata in tablet form purchased from Chicago pharmacies also showed the presence of methyl- and ethylparabens. To determine whether these compounds were natural chemical constituents of the plant, pharmacopoeial reference A. paniculata plant powder as well as samples of authenticated A. paniculata plant materials collected from Indonesia, Hong Kong, and mainland China were obtained and analyzed by HPLC-tandem mass spectrometry (LC-MS-MS). LC-MS-MS analyses confirmed the presence of trace concentrations (<0.0008% w/w) of p-hydroxybenzoic acid methyl ester but no p-hydroxybenzoic acid ethyl or propyl esters in these plant samples. The limits of detection of the LC-MS-MS assay for these compounds were 5 pg on-column and 5 ppb in the plant material. The levels of these p-hydroxybenzoic acid esters measured in the commercial products of A. paniculata suggest that they were introduced inadvertently during processing or as artificial additives.
Li
Wenkui
W
Program for Collaborative Research in the Pharmaceutical Sciences and Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, 833 S. Wood Street, Chicago, IL 60612, USA.
Sun
Yongkai
Y
Joseph
Joy
J
Fitzloff
John F
JF
Fong
Harry H S
HH
van Breemen
Richard B
RB
D035685:Andrographis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004340:Drug Contamination; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010226:Parabens / Q000032:analysis*; D010936:Plant Extracts / Q000737:chemistry*; D028321:Plant Preparations / Q000737:chemistry*; D011786:Quality Control
D010226:Parabens; D010936:Plant Extracts; D028321:Plant Preparations; C038193:4-hydroxybenzoic acid