[Enzyme immunoassay of usnic acid in lichens]

An enzyme immunoassay for usnic acid in lichens was developed, the sensitivity of which was 0.1 microg/g of air-dried material (0.00001%). Polyclonal rabbit antibodies against bovine serum albumin conjugated to (+)-usnic acid under the conditions of formaldehyde condensation made it possible to determine the analyzed substance in solutions at concentrations from 1 ng/mL when it interacts with an immobilized gelatin conjugate homologous in the binding mode. Usnic acid in 2-26600 microg/g (0.0002-2.6%) amounts was found in all 236 studied samples of lichens belonging to 53 species and 8 families.