Authentication and investigation of potential hepatotoxicity of Black Cohosh

Abstract

Black Cohosh (Actaea racemosa) is one of the highest selling medicinal plants, ranking as the sixth best seller in the US in 2015 (Smith et al., 2016). However, this popularity has been tarnished by claims of hepatotoxicity. The investigation of these reports has determined that implicated products did not contain Black Cohosh plant material. Other reports were shown to be incomplete or had other factors contributing. This has led to the suspicion that cases of adverse reactions may in fact be linked to cases of substitution or adulterations with Asian species of Actaea, rather than to A. racemosa. (Jordan et al., 2010). This shows the need for authentication of Black Cohosh products. In this study various DNA based authentication methods were developed. The first, PlantID is capable of discriminating between Actaea racemosa and four potential adulterant species; Actaea cimicifuga, Actaea cordifolia, Actaea podocarpa and Caulophyllum thalictroides, in a single PCR reaction. The resulting fragments are scrutinized using gel electrophoresis. Other platforms of analysis were trialled with little success. The second was a qPCR based method. These assays are competent in detecting A. racemosa, A. cimicifuga and A. dahurica species and are compared to a generic primer capable of amplification of ten Actaea species. This enables the user to detect specific species in comparison to how much Actaea species are present as a whole. This assay was extensively tested on many materials and products available in the UK and the USA. Out of 34 products assessed it was possible to extract DNA from 32. From the UK market it was found that five products contained undeclared species. From the US market it was found that six products contained undeclared species. All of the THR registered products were found to contain only the authentic species Actaea racemosa. This was a reassuring result from the analysis and adds further value to the scheme of THR. Sequence data from GenBank was used to assist in assigning species to sequenced DNA samples. The data contained on GenBank was scrutinised using various bioinformatics tools. Sequences were organised into molecular taxonomic units using tree diagram software. This showed efficiently and iii visually which sequence entries were reliable to use based upon grouping. This analysis showed that the nuclear internal transcribed spacer (nrITS) was an ideal barcoding region and that maturase K (MatK) was a poor choice for Actaea species. To address the issue of hepatotoxicity claims, cultured human hepatocyte derived cells were treated with 60% ethanol extracts of Actaea racemosa and Asian Actaea. A qPCR array was utilised to assess 84 genes associated with hepatotoxicity across various concentrations of extract. The collective array output gave a plethora of data which was analysed using bespoke online software from the manufacturer. Stringent quality controls were included on the arrays which gave confidence of results. There were small changes noted for Actaea racemosa and some activity for the Asian Actaea treated cells was also seen. An LDH and MTT assay were used to assess cell viability and toxicity in two human hepatocyte derived cell lines. Actaea racemosa showed no significant effects whereas the Asian Actaea extract showed a notable decrease in cell viability and significant release of LDH indicating toxicity. The Asian Actaea material used to manufacture extracts was of questionable species origin but determined to be either A. dahurica or A. cimicifuga. The results from these experiments were unfortunately not as conclusive as hoped, but did show some evidence of a more likely culprit of toxicity originating from Asian Actaea species.