TLC screen for maysin, chlorogenic acid, and other possible resistance factors to the fall armyworm and the corn earworm in Zea mays

A thin-layer chromatographic method has been developed for the analysis of maysin, a flavonoid C-glycoside, and its analogues, which have been implicated as resistance factors for the corn earworm (Helicoverpa zea, formerly Heliothis zea) and the fall armyworm (Spodoptera frugiperda). Boric acid present on the TLC plate enhances the fluorescence of luteolins, including maysin, and increases sensitivity to these compounds by a factor of 10 or more. Another resistance factor, found in smaller amounts, chlorogenic acid, interferes with maysin unless the developing solvent is made basic with dilute ammonium hydroxide or the TLC plate is treated with boric acid. Leaves, the major food source of the fall armyworm on corn, were not as readily analyzed because of interference due to streaking of the TLC plate.