100 years later, new ergot alkaloids are still being discovered

The application of highly sensitive multiresidue myco- toxin analysis by LC/MS-MS together with the availability of pure ergot alkaloid standards enabled us to expand the ergot alkaloid profile beyond the previously known alkaloid composition of C. africana.

Despite it being now over one hundred years after the beginnings of ergot alkaloid identification, new EAs are still being discovered in recent years. In 2015, an outbreak analysis of ergot-infected Sorghum crops in Israel led to the unexpected discovery of alkaloids not previously thought to occur naturally in Claviceps, along with the presence of other alkaloids that had not previously been reported to be produced by that species.

A number of assessments were performed for samples obtained from the afflicted sorghum fields: epidemiological investigation, species identification, ergot alkaloid profile analysis and mycotoxin analysis (of other parasitic fungi present). This was primarily for the purposes of determining the origin of the outbreak and the safety measures required following the Israeli Ministry of Agriculture’s quarantine of the sorghum fields.

The epidemiological investigation led to the conclusion that the outbreak resulted from exports of sorghum seed from a contaminated region in Texas. The species was identified as C. africana, following PCR analysis. It is important to note that primers were designed for only three Claviceps species commonly known to parasitise sorghum, hence ruling out the possibility of identifying novel Claviceps species (although this was not the primary goal of the investigation).

Ergot alkaloid identification was carried out via two forms of liquid chromatography: High-Performance Liquid Chromatography (HPLC) for quantitative detection of the target compounds, and Liquid Chromatography-Mass Spectrometry (LC-MS) for qualitative confirmation of the specific compounds (in this case DHL and DHLA) based on their mass-to-charge ratios in comparison to a reference standard.

In agreement with the literature, the most abundant EA detected by these analyses was dihydroergosine, making up about 90% of C. africana’s EA profile. It was also present in concentrations below the regulatory threshold for toxicity and thus meant that crops were safe for use in feed for livestock.

Completely unexpected, however, was that dihydrolysergol (DHL) constituted more than 36% of the EA profile. Before this, DHL has never been identified in C. africana.

Furthermore, traces of dihydroergotamine were also found, an alkaloid previously thought to be semi-synthetic. These results instead suggest that C. africana is able to produce it naturally, but by what mechanism is unknown.

While the authors did not dwell on their unexpected discovery, the ability of C. africana to produce dihydroergotamine gives rise to important future directions for research.

One example of an application of these findings is that C. africana could be used as a natural host for this pharmaceutically significant compound. Along with other EA-derived analgesics, dihydroergotamine is used to treat migraines and is semi-synthesized from its precursor, ergotamine. Hence, characterising the enzymatic and genetic basis for its biosynthesis, and incorporating recent synthetic biology advances such as Agrobacterium-mediated transformation for Claviceps, could have implications for yield optimization in an industrial as well as pharmaceutical context.

Reference:

1. Shimshoni, J., Cuneah, O., Sulyok, M., Krska, R., Sionov, E., Barel, S., & Meller Harel, Y. (2017). Newly discovered ergot alkaloids in Sorghum ergot Claviceps africana occurring for the first time in Israel. Food Chemistry, 219(C), 459–467. https://doi.org/10.1016/j.foodchem.2016.09.182