Proanthocyanidins Used in Studies
Based on the available evidence, the specific proanthocyanidins studied vary by source and research focus, with grape seed proanthocyanidins being the most extensively characterized and cranberry proanthocyanidins (PACs) being the most clinically studied for urinary tract health.
Grape Seed Proanthocyanidins
Composition and Structure
- Grape seed extracts contain proanthocyanidins composed of flavan-3-ol monomers including (+)-catechin, (-)-epicatechin, and (-)-epicatechin-3-O-gallate 1, 2
- Oligomers identified include B1, B2, B3, and B4 dimers, as well as trimer C1 2
- The degree of polymerization ranges widely, with studies documenting PAs up to a degree of polymerization (DP) of 28 1
- Galloylation varies significantly, with pentagallates (5 galloyl groups) in lower DP fractions and octagallates (8 galloyl groups) in higher DP fractions 1
Specific Fractions Studied
- Research has isolated fractions with mean degree of polymerization (mDP) of 3 (Sdp3) and mDP of 9 (Sdp9) from Vitis vinifera cv. Shiraz grape seeds 1
- These fractions were characterized using electrospray ionization mass spectrometry, revealing complex molecular distributions 1
Biological Activity Research
- Grape seed proanthocyanidins at doses of 1.680,3.375, or 6.750 mg/mL were tested for genotoxicity and antigenotoxicity in Drosophila melanogaster models 3
- For vascular protection in diabetic rats, 3 mg/kg/day of grape seed extract was administered, demonstrating endothelial protective effects 4
Cranberry Proanthocyanidins (PACs)
Clinical Dosing
- 36-37 mg of proanthocyanidins (PACs) daily, typically given as 18.5 mg twice daily, in standardized extracts for UTI prevention 5, 6
- One study used 500 mg cranberry fruit powder daily containing PAC 2.8 mg, showing significant UTI reduction 5
- Another formulation tested was 800 mg cranberry extract twice daily in catheterized patients 5
Standardization Challenges
- Commercial cranberry products often lack standardization of PAC content, making consistent dosing difficult 5, 6
- The active ingredient (PACs) varies significantly between products, and many research formulations are not commercially available 5
Other Food Source Proanthocyanidins
Pomegranate
- Total pomegranate tannin (a type of proanthocyanidin) was studied and compared to whole pomegranate juice for antiproliferative and antioxidant activities 7
Chocolate/Cocoa
- Cocoa contains polymeric proanthocyanidins along with flavanols such as catechin 7
- The Chinese Nutrition Society recommends 200 mg/day proanthocyanidins with an upper limit of 800 mg/day for general health purposes 7
Catechin Mixtures
- Studies examined 3:1 mixtures of catechin:ascorbic acid for optimal antioxidant activity, while 1:2 mixtures produced pro-oxidant effects 7
Key Distinctions
The proanthocyanidins studied differ fundamentally by: