Dimeric and trimeric hydrolyzable tannins from Quercus coccifera and Quercus suber

Area of Science:

• Phytochemistry
• Natural Product Chemistry
• Organic Chemistry

Background:

• Hydrolyzable tannins are a significant class of plant secondary metabolites with diverse biological activities.
• Quercus species are known sources of various tannins, but their structural diversity remains incompletely explored.

Purpose of the Study:

• To isolate and characterize novel hydrolyzable tannins from the leaves of Quercus coccifera and Quercus suber.
• To elucidate the unique oligomeric structures of these newly identified compounds.

Main Methods:

• Extraction and isolation of compounds from plant materials.
• Spectroscopic methods (e.g., NMR, MS) for structural elucidation.
• Chemical evidence to confirm structural assignments.

Main Results:

• Three new hydrolyzable tannins, cocciferins D(1) (1), D(2) (2), and T(1) (4), were isolated from Quercus coccifera leaves.
• Cocciferin D(2) (2), along with two additional new tannins, cocciferins D(3) (3) and T(2) (5), were obtained from Quercus suber leaves.
• Compounds 2, 3, and 5 were identified as rare oligomers with glucose cores in both open-chain and pyranose forms.

Conclusions:

• The study successfully identified five new hydrolyzable tannins, expanding the known chemical diversity within the Quercus genus.
• The unique structural features of cocciferins D(2), D(3), and T(2), particularly their glucose cores, represent a rare oligomeric tannin motif.
• These findings contribute to the understanding of tannin biosynthesis and chemistry, potentially paving the way for new applications.