Occurrence and analysis of mycotoxins in domestic Chinese herbal medicines.

For time immemorial, Chinese herbal medicines (CHMs) have been widely used in China for disease treatment and promotion of general well-being. However, in recent years, many studies have shown that mycotoxins produced by fungi could contaminate CHMs due to unfavourable pre- or post-harvest conditions, raising major concern for consumer safety. At present, there is a significant focus on developing novel mycotoxin detection methods for analysing CHMs, and numerous studies have aimed to determine which kinds of raw herbal materials are most susceptible to mycotoxin contamination. In this review, we focus on recent advances in understanding and detection of mycotoxins in domestic raw herbal materials and related products from 2000 to 2018. Aspects of mycotoxin contamination of CHMs covered in this review include common mycotoxin contaminants in CHMs, maximum mycotoxin residue limits, analytical methods for mycotoxin detection and their applications and limitations, as well as a brief discussion of the trends in ongoing research.

[Preparation of highly sensitive monoclonal antibody against aflatoxin B_1 and its application in rapid detection of contamination in Ziziphi Spinosae Semen].

A highly sensitive monoclonal antibody against aflatoxin B_1(AFB_1) was prepared and an indirect competition enzyme-linked immunosorbent assay(ic-ELISA) was established based on the antibody which was used for high-throughput and rapid screening of AFB_1 contamination in Chinese herbal medicines to ensure the safety of medication. In this study, the structure of AFB_1 was modified by improved oxime method, and the carrier protein was coupled by EDC-NHS method to obtain the complete antigen of AFB_1, which was more convenient and environmental friendly. The Balb/c female mice were immunized using increasing the immunization dose and various ways of injection, and finally the AFB_1 monoclonal antibody was prepared. The AFB_1 monoclonal antibody belongs to IgG_(2 b) immunoglobulin by identifying its immunological characteristics, and its sensitivity(IC_(50)) can reach 0.15 µg·L~(-1), and the affi-nity is 2.81×10~8 L·mol~(-1). The cross-reaction rates of AFB_2, AFG_1, and AFG_2 were 35.07%, 8.75%, and 1.15%, respectively, and there was almost no cross-reactivity with other mycotoxins. Based on the high sensitivity and specificity of the antibody, an ic-ELISA method was established and applied to the determination of AFB_1 contamination in Ziziphi Spinosae Semen. According to the matrix matching standard curve, the linear concentration range for AFB_1 was 0.05-0.58 µg·L~(-1)(R~2=0.992), the recoveries were 88.00%-119.0%, and the detection limit was 1.69 µg·kg~(-1). The AFB_1 in 33 batches of Ziziphi Spinosae Semen samples was determined by ic-ELISA, and the contamination level was 3.62-206.58 µg·kg~(-1). The linear correlation coefficient between the detection results of ic-ELISA and UHPLC-MS/MS was 0.996, and there were no false positive and false negative cases. It indicates that the established ic-ELISA is accurate and reliable, and could provide a simple and effective technique for fast screening of AFB_1 contamination in Ziziphi Spinosae Semen, and also could be considered as the reference for the detection and monitoring of AFB_1 contamination in other Chinese herbal medicines.

[High-throughput screening of ochratoxin A in Chinese herbal medicines using enzyme-linked immunoassay].

An indirect competitive enzyme-linked immunosorbent assay( ic-ELISA) was developed for the rapid detection of ochratoxin A( OTA) in nutmeg( Myristicae Semen),ginger( Zingiberis Rhizoma) and turmeric( Curcumae Longae Rhizoma). The matrix matching standard curve was used instead of the standard curve of sample diluent,and the sample extract and sample diluent were optimized. The sensitivity( IC_(50)) of this method for OTA in nutmeg,ginger and turmeric were determined as 0. 146,0. 157 and 0. 153 ng·m L~(-1),respectively and the limits of detection( LODs) were 0. 040,0. 032 and 0. 031 ng·m L~(-1),respectively. The recovery of samples ranged from 75. 99% to 122. 3%,with RSD<10%. Two positive samples for nutmeg and one positive sample for turmeric occurred in 50 samples,and the highest OTA contamination value was 1 167. 8 µg·kg~(-1). The results were further confirmed by LC-MS/MS. It shows that the developed ic-ELISA method is simple,rapid and sensitive,and can be applied for rapid and high-throughput screening of OTA in nutmeg,ginger and turmeric,as well as some other CHMs.