Substitution pattern elucidation of hydroxypropyl Pinus pinaster (Ait.) bark polyflavonoid derivatives by...

Area of Science:

• Plant biochemistry
• Polymer chemistry
• Analytical chemistry

Background:

• Condensed tannins (CTs) are complex polyphenolic compounds found in plant bark.
• Understanding CT structure is crucial for their applications in various industries.
• Hydroxypropylation modifies CT properties, but their detailed structure remains largely uncharacterized.

Purpose of the Study:

• To characterize the structure of Pinus pinaster bark CTs.
• To analyze the structure of hydroxypropylated CT derivatives with varying degrees of substitution.
• To elucidate the hydroxypropylation patterns and reactivity of CTs.

Main Methods:

• Negative-ion mode electrospray ionization tandem mass spectrometry (ESI(-)-MS/MS).
• Analysis of fragmentation patterns to determine monomeric units, oligomer sizes, and substituent distribution.
• Multistage experiments to establish hydroxyl group reactivity.

Main Results:

• Pinus pinaster bark CTs exhibit structural homogeneity with catechin as the monomeric unit, forming oligomers from dimers to heptamers.
• Hydroxypropylated CT derivatives showed characteristic fragmentation patterns.
• Preferential hydroxypropylation occurred at specific positions, with a defined reactivity order of hydroxyl groups (A-ring ≥ B-ring > C-ring).
• High structural heterogeneity was observed in the modified CT oligomers.

Conclusions:

• ESI(-)-MS/MS is effective for characterizing CTs and their derivatives.
• Hydroxypropylation leads to specific substitution patterns and introduces structural heterogeneity in CTs.
• The established reactivity order provides insights into the modification mechanisms of CTs.