THERMAL-DECOMPOSITION OF CAFFEIC ACID IN MODEL SYSTEMS - IDENTIFICATION OF NOVEL TETRAOXYGENATED PHENYLINDAN ISOMERS AND THEIR STABILITY INAQUEOUS-SOLUTION

Caffeic acid subjected to mild pyrolysis (225-226 degrees C) under vac uum resulted in rapid decarboxylation and the formation of simple cate chol monomers as well as more complex cyclocondensed dimers and polyme rs. This reaction yielded the same spectrum of products as did acid-ca talyzed cyclization of caffeic acid. The major pyrolysis products were identified by reversed-phase HPLC and LC-tandem mass spectrometry. Tw o novel compounds, identified by MS, H-1 NMR, and C-13 NMR as 1,3-cis- and 1,3-trans-tetraoxygenated phenylindans, were present as major pro ducts in both the caffeic acid pyrolysate and the acid-treated sample. The stability and reactivity of the pyrolysis products in weakly buff ered aqueous solutions were determined concomitantly by measuring hydr ogen peroxide generation and by monitoring the concentration of the in dividual components by reversed-phase HPLC. Such model studies may pro vide information pertaining to reaction mechanisms and the nature of t he compounds involved in hydrogen peroxide formation in coffee.