Proanthocyanidin Oligomers with Doubly Linked (A‐Type) Interflavan Connectivity

Ohmori, Ken; Suzuki, Keisuke

doi:10.1002/9781119545958.ch2

Cited by 2 publications

(3 citation statements)

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“…This can be attributed to their additional ether bond, which enhances conformational stability. Moreover, A-type linkage is associated with a reduction of atropisomeric effects as well as increased chemical stability over B-type PACs, as shown in some studies. , Whereas the exact biosynthetic mechanism for the formation of the additional A-type ether linkage remains to be determined, several attempts have been made to afford these unique structures in a controlled manner, for example, via chemical synthesis utilizing acyclic precursor monomers of the constituent flavan-3-ols, as well as through total synthesis. , Moreover, radical-mediated or enzyme-catalyzed reactions using reagents such as hydrogen peroxide, 1,1-diphenyl-2-picrylhydrazyl (DPPH), polyphenol oxidase, and xanthine oxidase have been reported to convert B-type to A-type PACs, expected with low yields. − …”

Section: Introductionmentioning

confidence: 99%

“…14,15 Whereas the exact biosynthetic mechanism for the formation of the additional A-type ether linkage remains to be determined, 16 several attempts have been made to afford these unique structures in a controlled manner, for example, via chemical synthesis utilizing acyclic precursor monomers of the constituent flavan-3-ols, as well as through total synthesis. 17,18 Moreover, radical-mediated or enzyme-catalyzed reactions using reagents such as hydrogen peroxide, 1,1-diphenyl-2picrylhydrazyl (DPPH), polyphenol oxidase, and xanthine oxidase have been reported to convert B-type to A-type PACs, expected with low yields. 19−22 Herein, trimeric and tetrameric A-type PACs were prepared via oxidative conversion from their naturally abundant precursors using DPPH to expand the PAC SAR knowledge via dentin biological and concurrent computer modeling studies.…”

Section: ■ Introductionmentioning

confidence: 99%

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Chemical Transformation of B- to A-type Proanthocyanidins and 3D Structural Implications

Jing,

McDermott,

Flanders

et al. 2024

J. Nat. Prod.

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In nature, proanthocyanidins (PACs) with A-type linkages are relatively rare, likely due to biosynthetic constraints in the formation of additional ether bonds to be introduced into the more common B-type precursors. However, A-type linkages confer greater structural rigidity on PACs than do B-type linkages. Prior investigations into the structure−activity relationships (SAR) describing how plant-derived PACs with B-and complex AB-type linkages affect their capacity for dentin biomodification indicate that a higher ratio of double linkages leads to a greater interaction with dentin type I collagen. Thus, A-type PACs emerge as particularly intriguing candidates for interventional functional biomaterials. This study employed a free-radical-mediated oxidation using DPPH to transform trimeric and tetrameric B-type PACs, 2 and 4, respectively, into their exclusively A-type linked analogues, 3 and 5, respectively. The structures and absolute configurations of the semisynthetic products, including the new all-A-type tetramer 5, were determined by comprehensive spectroscopic analysis. Additionally, molecular modeling investigated the conformational characteristics of all trimers and tetramers, 1−5. Our findings suggest that the specific interflavan linkages significantly impact the flexibility and low-energy conformations of the connected monomeric units, which conversely can affect the bioactive conformations relevant for dentin biomodification.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Chemical Transformation of B- to A-type Proanthocyanidins and 3D Structural Implications

Jing,

McDermott,

Flanders

et al. 2024

J. Nat. Prod.

View full text Add to dashboard Cite

show abstract

“…Their molecular diversity is further enhanced by the degree of oligomerization and connectivity pattern. 3 Note that the two flavan-3-ol units in 1 and 2 are connected through a C4–C8′ bond. Similarly, OPAs comprising the connectivity through C4–C6′ bond (not shown) are also present in Nature.…”

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confidence: 99%