Novel Epicuticular Leaf Flavonoids from Kalmia and Gaidtheria (Ericaceae)

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-diCH3flavone (kalmiatin), 5-OH-3,7,4'-triOMe-6-CH3-flavone (8-desmethyl-kalmiatin), 5,4'-diOH-3,7diOMe-6,8-diCH3-flavone (latifolin) and 5,4'-diOH-3,7-diOMe-6-CH3-flavone (8-desmethyllatifolin) 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-desmethyllatifolin 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.