Acylphloroglucinols and flavonoid aglycones produced by external glands on the leaves of two dryopteris ferns and currania robertiana

The sparse resinous leaf exudates of Dryopteris villarii and D. arguta contain acylphloroglucinols that have previously only been found in the rhizomes of Dryopteris species. The phloroglucinol derivatives were characterized as representatives of the para-aspidin, desaspidin and albaspidin series by 2-D NMR spectroscopy and atmospheric pressure chemical ionization mass spectrometry (APCI-MS-MS). Mass fragmentation proved to be of diagnostic value to identify the acyl side chains and also allowed distinction between desaspidins and isomeric albaspidin analogues. The frond exudate of Currania robertiana was devoid of acylphloroglucinols, but was found to contain flavonoid aglycones. The acylphloroglucinols and flavonoid aglycones are presumably produced by external glands on the leaves, the presence and ultrastructure of which was examined by scanning electron microscopy.