Rapid detection of synthetic adulterants in Indonesian herbal medicines using ATR-FTIR spectroscopy combined with chemometrics

Herbal medicines have been gaining popularity as alternative medicines in recent years, including in Indonesia. Synthetic drug compounds can be illegally included in herbal medicines to achieve a faster effect. Detection of synthetic drugs in adulterated herbal products is important because of the negative side effects associated with shortand long-term use. Sildenafil, phenylbutazone, and sibutramine HCl are common adulterants in Indonesian herbal products intended to promote sexual arousal and performance, relieve muscle pain, and reduce weight. The aim of this study was the rapid and cost-effective detection of sildenafil citrate, phenylbutazone, and sibutramine HCl in Indonesian herbal products and herbal drug preparations by Attenuated Total Reflectance-Fourier Transmission Infrared Spectrometer (ATR-FTIR) spectroscopy combined with chemometrics. Herbs (aphrodisiac, muscle pain relieving and slimming herbs) and medicinal plants (Pasak Bumi (Eurycoma longifolia Jack.) roots, black pepper (Piper nigrum L.) leaves and West Indian Elm (Guazuma ulmifolia Lamk.) leaves) were intentionally adulterated with synthetic drug compounds in the range of 0-40% (w/w). ATR-FTIR spectra were recorded for all unadulterated and adulterated samples at 4000-650 cm-1. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to analyze the spectra of the unadulterated and adulterated samples. All samples were successfully classified with respect to their synthetic compound content. The presence of sildenafil, phenylbutazone and sibutramine can be rapidly detected with simple and non-destructive sample preparation using ATR-FTIR spectroscopy in combination with chemometrics. In conclusion, this method can be used for screening sildenafil citrate, phenylbutazone and sibutramine HCl adulterants in herbal products and herbal powders.