A new approach for identification of medicinal almonds by fourier transform infrared spectroscopy and systematic clustering of characteristic peaks

Medicinal almonds have been used for over 2 000 years and its clinical efficacy includes relieving cough and asthma. The domestic market in China is flooded with different kinds of dried almonds, such as bitter almond (Armeniacae Semen Amarum, AAS), sweet almond (Armeniacae Semen Dulce, ADS), salted almond (Armeniacae Semen Salsa, ASS), and their sulfur-fumigating products (Armeniacae Semen Sulphur Fumabat, ASFS). Wide varieties of almonds may lead to uncertain efficacy, aberrant quality, and even increased safety risk. However, the authentication method for medicinal almonds has not been reported, although imposters may lead to ineffective medical response. In the present study, Fourier transform infrared spectroscopy (FTIR) and the 2-dimensional infrared (2D-IR) spectroscopy were used to identify different almonds, which were extracted with different solvents including water, methanol, ethanol, chloroform and ethyl acetate, respectively. A new simple FTIR method was developed in the present study. According to the gradient solvent polarity, a new 2D IR method was first developed, and the commodities of almonds in China were analyzed by using the FTIR spectroscopy supported by hierarchical clustering of characteristic peaks. Moreover, 5-hydroxymethyl-2-furfural could be used as a detection index and control target in the quality control of medicinal almonds.