Quality evaluation of natural Cordyceps sinensis from different collecting places in China by the contents of nucleosides and heavy metals

Safety and efficacy are two key important aspects for the quality assessment of health-food products. Cordyceps sinensis, which has multiple pharmacological activities, is one of the most expensive traditional Chinese medicines (TCMs) and is used frequently in health-food products in China. Usually, nucleosides and their related compounds have been used as markers for evaluation of the quality of natural and/or cultured Cordyceps. However, heavy metals should also be considered as they may affect the safety of clinical use. In the present study, the contents of six nucleosides (adenosine, cytidine, guanosine, uridine, inosine and thymidine), six nucleobases (adenine, cytosine, guanine, uracil, hypoxanthine and thymine) and five nucleotides (adenosine-5'-monophosphate (AMP), cytidine-5'-monophosphate (CMP), guanosine-5'-monophosphate (GMP), uridine-5'-monophosphate (UMP), and thymidine-5'-monophosphate (TMP)) in natural C. sinensis samples from different collecting places were simultaneously determined by a validated HPLC-DAD method. At the same time, six heavy metals including Hg, As, Cr, Cd, Cu and Pb in natural C. sinensis and their related soil samples were determined by atomic absorption spectrometry (AAS). The results showed that the total content of nucleosides and their related compounds, as well as the individual levels of nucleotides, are much higher in fresh samples (collected in 2012) as compared to stored samples (collected in 2011). Therefore, the storage conditions may affect on the quality of natural C. sinensis. On the other hand, the total and individual contents of heavy metals vary in different Cordyceps and soil samples, but the levels of As and Cu in Cordyceps are correlated well with the soil samples from their collection locations. Therefore, the high levels of heavy metals, especially As and Cu, in natural Cordyceps originate from the soil of the producing areas.