Oolong tea has traditionally been manufactured from
tea leaves via a semi-fermentation process. Flavan-3-ols,
including catechins, which are major polyphenols in tea leaves, undergo a complex type of polymerization by
both polyphenol oxidases and heat treatment in this
process, and are converted to the high-molecular-weight
oolong tea polymerized polyphenols (OTPP) charactering
oolong tea. Recently, we successfully isolated OTPP
from oolong tea extract by reversed-phase HPLC, and
found that OTPP inhibited pancreatic lipase more effectively
than oolong tea extract in vitro.