Bioaccessibility and risk assessment of heavy metals, and analysis of arsenic speciation in Cordyceps sinensis .

Background: Cordyceps sinensis ( C. sinensis ) is a famous and precious Traditional Chinese Medicine (TCM), while frequent reports of heavy metals, especially arsenic, exceeding standards in C. sinensis in recent years have raised concerns of its safety. Therefore, it is urgent for a research on heavy metals (Cu, Pb, As, Cd, Hg) in C. sinensis , of its bioaccessibility, dietary exposure estimation, arsenic speciation analysis and health risks assessment to human body.

Methods: Three 30 g batches of mixed wild growth C. sinensis samples were collected from Qinghai Province and each batch were divided into three parts: the whole C. sinensis , the stroma and the caterpillar body. The in vitro gastrointestinal method was used to evaluate the bioaccessibility of the heavy metals in the samples. The arsenic speciation analysis in the in vitro gastrointestinal solutions and dilute nitric acid extracted solutions were conducted using high performance liquid chromatography-inductively coupled plasma mass (HPLC-ICP-MS) method. Finally, the target hazard quotient (THQ) developed by the US EPA (1989) was used to assess the health risks of heavy metals in C. sinensis .

Results: The contents of Cu, Pb, Cd and Hg in the stroma were higher than those in the caterpillar body. In contrast, As was mainly found in the caterpillar body. In the whole C. sinensis , the average bio-accessibilities of Cu, Pb, As, Hg and Cd were 41.29, 40.11, 64.46, 18.91, and 81.14%, respectively. While in the caterpillar body, the corresponding bio-accessibilities values were 48.26, 42.92, 66.15, 12.86, 87.07%, respectively, and were 38.30, 30.53, 30.18, 7.46, and 82.30%, respectively in the stroma part. Different arsenic speciations of arsenite [As(III)], arsenate [As(V)] and trace amounts of methylarsonic acid [MMA] were detected. Of the total As, 8.69% was in inorganic form, which was also the major form of dissolved As. Among the extracted inorganic species, the concentrations of As(III) and As(V) were 0.56 ± 0.16 and 0.29 ± 0.06 mg kg-1 , respectively. In the gastrointestinal solutions, only As(III) and As(V) could be detected; the sum content of the two species was 2.00-2.73%. The bioaccessibility target hazard quotient (BTHQ) values for Cu, Pb, As, Cd and Hg in C. sinensis were 0.0041, 0.0040, 0.5334, 0.0020 and 0.0005, respectively, all less than 1.

Conclusion: None of the five heavy metals in C. sinensis can be 100% absorbed by human body. The content of arsenic in C. sinensis is high, but the strong toxic inorganic arsenic accounted for only 8.69%. The heavy metals in C. sinensis presented no obvious risks to human health in a reasonable taking way.