Sigillins from Springtails Are Potent Natural Insecticides

Sigillins are highly chlorinated
natural products from the springtail Ceratophysella sigillata (Collembola) that are used to deter
arthropod predators. We report here the isolation and structure elucidation
of sigillin F, a hydrogenated benzopyranone compound bearing two trichloromethyl
groups, and the synthesis of trideoxysigillin (8), a
non-natural compound representing the basic scaffold of the sigillins.
Sigillins A and F showed insecticidal activity toward various insects,
similar to the commercial insecticide imidacloprid, whereas 8 was inactive. The highest mortality was observed for the
aphids Megoura viciae and Myzus persicae, but other insect species were also susceptible. Sigillins act as
noncompetitive antagonists of the GABA receptor. This mode of action
is identical to that of known insecticides with high chlorine content
such as dieldrin or endosulfan. The high content of sigillins in C. sigillata, more than 4 mM in concentration, indicates
self-resistance. Strikingly, the Collembola and humans have both arrived
at the same target with related types of compounds to combat insects.