Dioic acid glycosides, tannins and methylated ellagic acid glycosides from Morella salicifolia bark

The bark of Morella salicifolia (HOCHST. EX A. RICH.) VERDC. & POLHILL (Myricaceae) is a common herbal drug and especially utilized by the Maasai community of northeastern Tanzania. It is traditionally used to treat swellings on the cheek and face, cough, toothache, stomach problems, headaches, and skin diseases. Unless, there is still a lack of information considering the specialized metabolites that may be responsible for the traditional use of this medicinal plant. An isolation study on a methanolic extract revealed three methylated ellagic acids, castalagin, two monomeric flavan-3-ols, three prodelphinidins and three dioic acid glycosides. Among these metabolites, myriside (3,4-dimethyl ellagic acid 4'-O-beta-D-xylopyranoside, 1), epigallocatechin-3-O-gallate-(2 beta -> O -> 7, 4 beta -> 8)-gallocatechin (9), 2,7-dimethyl-8-O-(6'-O-galloyl)-beta-D-glucopyranoside-deca-2E,4E-dienedioic acid (10), 2,7-dimethyl-8-O-beta-D-glucopyranoside-deca-2E,4E-dienedioic acid (11) as well as 4,9-dimethyl 10-O-beta-D glucopyranoside-dodeca-2E,4E,6E-trienedioic acid (12) were isolated for the first time. To the best of our knowledge, the dioic acid glycosides represent a generally novel structure type. To provide comprehensive information on the condensed tannins, the polymeric proanthocyanidins were enriched and characterized via C-13-NMR. Results confirm chemo-taxonomic relationships within the genera Morella and Myrica in the Myricaceae.