MMP2 and rheumatoid arthritis: Theaflavin-3,3′-digallate (TFDG), derived from Camellia sinensis exerted anti-RA effects via downregulation of multinucleated osteoclast formation, MMP-9 and MMP-2 of osteoclast precursor cells and mature osteoclast of rats treated with a dose of 10 and 100 μM for 7 days [36].