Proanthocyanidins (Pine bark and grape seed extracts)

Proanthocyanidins are plant-based compounds called flavonoids. Proanthocyanidins are found in apples, maritime pine bark, cinnamon, aronia fruit, cocoa beans, grape seed, grape skin, the red wines of Vitis vinifera (the common grape), bilberry, cranberry, black currant, green tea, and black tea. They are known for their antioxidant activity which is 20 times more powerful than vitamin C and 50 times more potent than vitamin E.¹

One study found “that intraperitoneal injection of GSPE (grape seed proanthocyanidin extract) attenuated CIA (collagen-induced arthritis) in mice” and that “GSPE may be useful in the treatment of rheumatoid arthritis.”² The same study explains how GSPE might work:

GSPE treatment significantly reduced the numbers of tumor necrosis factor alpha (TNF-α)- or interleukin 17 (IL-17)-producing cells in the synovial tissue and the spontaneous production of TNF-α and IL-17 by splenocytes compared with those in the control mice²

Another study collaborated these findings:

PA (proanthocyanidins) has anti-inflammatory effect on experimental in rats and mice. Its mechanisms of anti-inflammation action are relevant to oxygen free radical scavnging, anti-lipid peroxidation, and inhibition of the formation of inflammatory cytokines.³

¹https://en.wikipedia.org/wiki/Proanthocyanidin
²https://www.sciencedirect.com/science/article/pii/S0165247809001187
³https://www.chinaphar.com/1671-4083/22/1117.pdf