Determination of total arsenic and inorganic arsenic content in 54 kinds of “medicine food homology” plants from China

Medicine food homology (MFH) has been applied for both food and medicine. However, the possible and adverse risks of MFH are associated with the arsenic element, leading to various health disorders, including hypertension, neurological disease, respiratory tract disease, cardiovascular disease, and even the lethal. Therefore, it is significantly important to determine the arsenic concentration of MFH plants for more accurate toxicological assessments. The present study aimed to investigate the content of total arsenic (t-As) and inorganic arsenic (AsIII and AsV). 54 kinds of MFH were collected from different provinces in China, namely Chinese prickly ash, tangerine peel, cinnamon, goji berry, mulberry, hawthorn berry, coix seed, lotus seed, licorice, Astragali radix, Platycodonis radix, clove, honeysuckle, chrysanthemum, rose, lily, mulberry leaf and Perilla frutescent, according to inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). In addition, the arsenic speciation analysis was also made to consider the precision, limit of detection (LOD), and limit of quantification (LOQ). The results show that: (1) The arsenic concentration of MFH varied greatly in the geographical origin, cultivars, and arsenic species. (2) The LOD/LOQ values of t-As, AsIII and AsV were 0.003/0.010, 0.004/0.012 and 0.004/0.012, respectively. The recovery rates of t-As and inorganic arsenic were 85.3%-88.0% and 94.90%-97.00%, respectively. (3) The concentration of t-As for the 54 kinds of MFH plants ranged from 0.005 to 1.627 mg/kg, which under the limited value (2 mg/kg), according to the regulation of Chinese Pharmacopoeia. Exceptionally, Chinese prickly ash (with the highest value) from Sichuan (3.407 mg/kg) was attributed to their contaminated sources. Specifically, the t-As of root MFH plants (0.039-0.370 mg/kg) significantly higher than that of seed (below LOD-0.081) (P<0.05). Most of the arsenic that is taken up during growth accumulated in roots and iron plaque around the roots via three main ways of symplast, apoplast, and plant vascular. Moreover, the highest t-As was observed among four types of flower samples (0.039-0.427 mg/kg), namely clove, honeysuckle, rose, and chrysanthemum, honeysuckle from Shanxi Province. While the minimum was found in the rose sample from Gansu province. Furthermore, the t-As of lily (0.019-0.035 mg/kg) was significantly lower than that of mulberry leaf (0.388-0.496 mg/kg) and Perilla frutescent (0.275-1.627 mg/kg) (P<0.05) in the leaf MFH plants. (4) Significant differences were found in the inorganic arsenic from all MFH plants (P<0.05). The concentration range of AsIII (<LOD to 0.092 mg/kg) was larger than that of AsV (<LOD to 0.584 mg/kg). Generally, AsIII was considered more toxic than AsV, in terms of the chemical form, oxidation state, methylation extent, and concentration. Honeysuckle from Shanxi and Chinese prickly ash from Sichuan also presented the highest AsIII and AsV, respectively. While there was no inorganic arsenic in the coix seed from Fujian/Liaoning, and rose from Shandong. AsIII was detected in some MFH samples, whereas there was no AsV. Therefore, it is necessary to determine t-As, AsIII, and AsV in the MFH plants from different regions. The finding can provide a strong reference to assess the arsenic risk in MFH for the food and pharmaceutical industries.