Since the long-term application of synthetic chemicals as insecticides and the chemotherapy
of protozoal diseases have had various negative effects (non-target effects, resistance),
research on less harmful biological products is underway. This review is focused on
lichens with potential insecticidal and antiprotozoal activity. Literature sources
(27) were surveyed from five bibliographic databases and analyzed according to the
taxonomic group of the insect, the protozoal disease and the lichen, the type of bioactive
compounds (including method of application and mount applied), and the potential bioactivity
based on mortalities caused after 24 h of exposure on insects and on parasitic protozoa.
Six species of protozoa and five species of mosquitoes, three kinds of larval stages
of insects and three protozoa stages were tested. Insecticidal and antiprotozoal effects
of crude extracts and seven lichen secondary metabolites (mostly usnic acid) of 32
lichen species were determined. Physiological and morphological changes on parasitic
protozoa were observed. Mortality rates caused by LSMs on insect vectors closer to
(or somewhat above) the WHO threshold were considered to be insecticides. The results
are based on laboratory experiments; however, the efficacy of metabolites should be
confirmed in the field and on non-human primates to control the insect vectors and
human protozoal diseases transmitted by insects.
