Quantification of benzoquinones in the flour beetles. Tribolium castaneum and Tribolium confusum.

Benzoquinones were extracted from flour beetles by rinsing them for 8 min in methanol followed by homogenization in fresh methanol. This procedure recovered > 96% of the total benzoquinones from both species, with the methanolic rinse and supernatant representing the "surface" and "total" benzoquinones. As determined by UV/VIS spectrometry and reversed-phase HPLC, the methanolic rinse contained methyl- and ethyl-1,4-benzoquinone (MBQ and EBQ), but no substituted hydroquinones, The methanolic supernatant contained MBQ and EBQ, and methyl- and ethyl-hydroquinone. When stored at -20 degrees C for 72 hr, the chemical composition of the methanolic rinse did not change, but the composition of the methanolic homogenate did change. Notably, the amounts of benzoquinones in the methanolic supernatant decreased during storage. The method described represents an improvement over those described previously in that it uses less hazardous solvents for extraction (methanol vs more non-polar solvents such as hexane) and allows for the differentiation and quantification of the surface and total benzoquinones of these beetles.