Uncaria gambir, a native Southeast Asian herbal plant, can mostly be found in countries such as Indonesia and Malaysia.1 It had been widely used as an astringent medicine for the treatment of spongy gums, tooth acne, diarrhea and sore throat.2 Besides being chewed, it is also imported in large quantities by the West for tanning, calico printing and dyeing purposes.3 Previous studies showed that gambir consists mostly of the flavan monomer, which contains (+)-catechin, (+)-epicatechin and alkaloids.4 Catechins are flavonoids (C6-C3-C6) that are mostly found in fruits and plants such as tea leaves, wine andpotatoes.5Interestingly, catechin exhibits an anti-oxidative activity that stops oxidation andcorrosion, the deterioration process and discoloration....