Mushroom Toxins - The Meixner Test

Mushrooms can be found extensively in a variety of natural environments and visual identification of mushroom species is well established. However, from a scientific point of view there are still key areas of mushroom research that warrant investigation.

This dissertation concentrated on two areas of mushroom science. The first area investigated was the chemistry of the Meixner test, a spot test widely used in the field by mycologists to facilitate the identification of Death Cap mushrooms (amatoxin). It is performed by applying small quantity of mushroom juice onto low quality lignin paper then adding concentrated hydrochloric acid. A positive spot test results in a blue colouration. The detailed chemistry of the test had not been elucidated to date. However, experiments and conditions investigated in this research suggest that a possible reaction in the Meixner test is substitution on the indole ring, present in all amatoxins. The research demonstrated the complexity of the underlying chemistry of the Meixner test. It was found that the type of paper used could affect the results, as the lignin structure is not consistent between different paper manufacturers. The complexity of the lignin structure makes it difficult to define the exact monolignol(s) which undergo the reaction yielding the blue colour of the spot.

The second area of this dissertation was to identify and collect local mushrooms. A mushroom stumpery was set up at the Food and Environment Research Agency. A protocol for mushroom identification, using up to date and currently available databases was also developed as part of this dissertation. The protocol can be used to help others identify mushrooms and ascertain if they are safe to eat. 156 different species of mushrooms were collected and many were reported with the assistance of The British Mycological Society.