CAFFEOYLTARTRONIC ACID FROM CATNIP (NEPETA-CATARIA) - A PRECURSOR FORCATECHOL IN LUBBER GRASSHOPPER (ROMALEA-GUTTATA) DEFENSIVE SECRETIONS

Adults of the lubber grasshopper (Romalea guttata) secrete increased a mounts of catechol from their defensive glands when fed diets containi ng only catnip leaves (Nepeta cataria). Model compound bioassays showe d that these insects were able to sequester and biomagnify simple phen ols, such as catechol and hydroquinone, in their defense gland secreti ons. Excessive catechol secretions from caffeic acid-fortified diets i ndicated metabolic pathways exist to perform efficiently more complex biochemical conversions. Reverse-phase HPLC of methanol extracts of ca tnip revealed only one major caffeoyl-polyphenol as a possible precurs or for the observed elevated catechol secretions, when this plant is f ed to lubbers. The compound was shown to be caffeoyltartronic acid (CT A). During analysis of CTA by probe-MS or gas chromatography (of its s ilylated derivative), CTA decomposed by loss of carbon dioxide to form caffeoylglycolic acid (CGA), making identification by these methods a mbiguous. Only fast atom bombardment mass spectrometry (FAB-MS, negati ve mode) gave a true molecular weight. Ground-ivy (Glecoma hederacea), a relative of catnip, was also shown to contain CTA. The mung bean (P haseolus radiatus = Vigna radiata), a species totally unrelated to cat nip, is the only other reported plant source of CTA. Catnip leaves wer e found to contain about twice as much CTA as mung bean leaves.