https://pubmed.ncbi.nlm.nih.gov/24745654/

ABSTRACT: The antioxidant activity (AA) of fruits and vegetables has been thoroughly investigated but less is known about
the AA of dietary supplements (DS). We therefore assessed the AA of three to five DS each from pomegranate, milk thistle,
green tea, grapes, goji, and acai using four widely used standard methods. The secondary objective was to determine the effects of
in vitro digestion on their AA. The AA of the DS prior to digestion ranked as follows: pomegranate > resveratrol > green tea >
grape seed > milk thistle and very low in goji and acai with significant group variability in AA. The AA after in vitro simulated
digestion of the mouth, stomach, and small intestine compared to undigested supplement was decreased for green tea and grape
seed but increased for pomegranate, resveratrol, milk thistle, goji, and acai to various extents. Although polyphenols provide the
major antioxidant potency of the tested supplements, our observations indicate that digestion may alter antioxidant properties
depending in part on the variations in polyphenol content.
KEYWORDS: pomegranate, antioxidant activity, in vitro digestion, dietary supplements, green tea, milk thistle, acai, goji, resveratrol,
grape seedVariability_in_the_Antioxidant_Activity