Catechins

Research & Evidence

Catechins are a group of astringent flavan-3-ol polyphenols. They are the dominant polyphenols of green tea — about 70% of its polyphenol content — and the most studied of the constituents covered here come from that plant, where EGCG (epigallocatechin-3-gallate) is the most abundant and most active member ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}. Reported activities from the source-herb monographs include:

• Antioxidant — catechins are potent free-radical scavengers and account for much of the antioxidant value of tea ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}, cat’s claw ^{2Reference 2Pilarski et al. · 2006Antioxidant activity of ethanolic and aqueous extracts of Uncaria tomentosa (Willd.) DC}, guarana ^{3Reference 3Basile et al. · 2005Antibacterial and antioxidant activities of ethanol extract from Paullinia cupana Mart} and sarsaparilla ^{6Reference 6Lu et al. · 2014Antioxidant and Anti-Inflammatory Activities of Phenolic-Enriched Extracts of Smilax glabraView study →}. In guarana and sarsaparilla the catechin and epicatechin fraction is specifically credited with the antioxidant character of the plant ^{3,6Reference 3Basile et al. · 2005Antibacterial and antioxidant activities of ethanol extract from Paullinia cupana MartReference 6Lu et al. · 2014Antioxidant and Anti-Inflammatory Activities of Phenolic-Enriched Extracts of Smilax glabraView study →}.
• Cardiovascular (ACE inhibition, endothelial and anti-atherosclerotic effects) — green-tea catechins (primarily EGC) significantly inhibit angiotensin-converting enzyme (ACE) and improve endothelial and vascular function ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}. In guarana, an aqueous extract inhibited platelet aggregation, an effect attributed to its procyanidin and catechin content ^{4Reference 4Schimpl et al. · 2013Guarana: revisiting a highly caffeinated plant from the Amazon}.
• Cholesterol and blood sugar — catechins lower cholesterol through both reduced absorption and increased faecal excretion, and have been shown to increase gene expression of bile-acid synthesis; EGCG also improves insulin sensitivity (reported as much as 13% in some studies) ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}.
• Anti-inflammatory — EGCG and related catechins reduce inflammation through cytokine inhibition and regulation of NADPH oxidases ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}.
• Antibacterial — the antibacterial activity of tea extracts (highest in green tea) is attributed to the catechin content and is reported to act against gram-positive bacteria ^{5Reference 5Chan et al. · 2011Antioxidant and antibacterial properties of green, black, and herbal teas of Camellia sinensis}.
• Neuroprotective — green-tea extracts produce neuroprotective effects in models of Parkinson’s disease, attributed to the anti-inflammatory and antioxidant profile of the catechins ^{7Reference 7Bitu Pinto et al. · 2015Neuroprotective properties of the standardized extract from Camellia sinensis (green tea) and its main bioactive components, epicatechin and epigallocatechin gallate, in the 6-OHDA model of Parkinson’s disease}.

A practical caveat noted across these sources is low oral absorption: only around 5% of consumed catechins appear in blood plasma, and much of the rest is transformed by colonic microbes into other metabolites ^{1Reference 1Moore et al. · 2009Green tea (Camellia sinensis) catechins and vascular function}. This means catechin-rich material generally needs to be taken at higher, more bitter, more concentrated doses than a casual cup of tea to deliver therapeutic effects.

Toxicity & Safety

Catechins are well tolerated and the plants that supply them — tea, cat’s claw, guarana and sarsaparilla — are all considered suitable for long-term use at normal doses. The most relevant caution is not toxicity but interaction: the astringent catechins can bind to and reduce the absorption of some drugs and nutrients taken at the same time. Catechin-rich tea also carries the caffeine cautions of its parent plant, though that reflects the caffeine rather than the catechins themselves.

References

1. Moore, R. J., Jackson, K. G., & Minihane, A. M. (2009). Green tea (Camellia sinensis) catechins and vascular function. British Journal of Nutrition, 102(12), 1790-1802.
2. Pilarski, R., Zieliński, H., Ciesiołka, D., & Gulewicz, K. (2006). Antioxidant activity of ethanolic and aqueous extracts of Uncaria tomentosa (Willd.) DC. Journal of ethnopharmacology, 104(1-2), 18-23.
3. Basile, A., Ferrara, L., Del Pezzo, M., Mele, G., Sorbo, S., Bassi, P., & Montesano, D. (2005). Antibacterial and antioxidant activities of ethanol extract from Paullinia cupana Mart. Journal of ethnopharmacology, 102(1), 32-36.
4. Schimpl, F. C., da Silva, J. F., de Carvalho Gonçalves, J. F., & Mazzafera, P. (2013). Guarana: revisiting a highly caffeinated plant from the Amazon. Journal of ethnopharmacology, 150(1), 14-31.
5. Chan, E. W., Soh, E. Y., Tie, P. P., & Law, Y. P. (2011). Antioxidant and antibacterial properties of green, black, and herbal teas of Camellia sinensis. Pharmacognosy research, 3(4), 266.
6. Lu, C., Zhu, W., Wang, M., Xu, X., & Lu, C. (2014). Antioxidant and Anti-Inflammatory Activities of Phenolic-Enriched Extracts of Smilax glabra. Evidence-Based Complementary and Alternative Medicine. Article ID 910438. http://dx.doi.org/10.1155/2014/910438
7. Bitu Pinto, N., da Silva Alexandre, B., Neves, K. R. T., Silva, A. H., Leal, L. K. A., & Viana, G. S. (2015). Neuroprotective properties of the standardized extract from Camellia sinensis (green tea) and its main bioactive components, epicatechin and epigallocatechin gallate, in the 6-OHDA model of Parkinson’s disease. Evidence-Based Complementary and Alternative Medicine, 2015.