Novel Epicuticular Leaf Flavonoids from Kalmia and Gaidtheria (Ericaceae)

Abstract

Abstract Leaves of a number of Ericaceous plants have a thin epicuticular layer that consists mostly of triterpenes. In Kalmia angustifolia, K. latifolia and K. polifolia as well as in Gaultheria procumbens and G. shallon this material also contains trace amounts of flavonoid aglycones. In Kalmia they are the 3-OMe-derivatives of four C-methyl flavones reported previously as the typical leaf-wax flavonoids of Eucalyptus. The new compounds, 5-OH-3,7,4′-triOMe-6,8-diCH 3 -flavone (kalmiatin), 5-OH-3,7,4′-triOMe-6-CH 3 -flavone (8-desmethyl-kalmiatin), 5,4′-diOH-3,7-diOMe-6,8-diCH 3 -flavone (latifolin) and 5,4′-diOH-3,7-diOMe-6-CH 3 -flavone (8-desmethyl-latifolin) are novel natural products. They could not be detected in eight species of Eucalyptus. A screening of 15 species of Ericaceae revealed that 8-desmethyl-sideroxylin and 8-desmethyl-latifolin are present also in the epicuticular layer on leaves of Gaultheria procumbens, while on G. shallon and on Andromeda polifolia traces of galangin-3-methyl ether were found. In the other species checked no external flavonoid aglycones could be detected.