Variability in the Antioxidant Activity of Dietary Supplements from Pomegranate, Milk Thistle, Green Tea, Grape Seed, Goji, and Acai: Effects of in Vitro Digestion

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.

Investigating the Physicochemical Properties and in Vitro Bioaccessibility of Phenolics and Antioxidant Capacity of Rooibos Herbal Tea Beverage

“…A possible reason of varying bioaccessibility of antioxidant capacity values could be associated with several factors related to the process conditions, chemical interactions with other phytochemicals, biomolecules present in the food and also the protocols used for the measurements (Parada and Aguilera, 2007). In agreement with our data, Henning et al (2014) reported a 21.5% and 8.1% decrement of TEAC (trolox equivalent antioxidant capacity) in green tea and grape seed samples during in vitro simulated digestion. In another study, Değirmencioğlu et al (2016) concluded DPPH bioaccessibilities of fermented vegetable juices between 16-32%.…”

Effects of in vitro digestion and in vitro colonic fermentation on stability and functional properties of yerba mate (Ilex paraguariensis A. St. Hil.) beverages

“…A recent work evaluated the effect of in vitro digestion on the antioxidant activity of dietary supplements from pomegranate, milk thistle, green tea, grape seed, goji and acai, all of them as extracts. The authors found that, except for green tea and grape extracts, no significant losses of antioxidant activities occurred during in vitro digestion (Henning et al, 2014).…”

Culinary Herbs and Spices: Their Bioactive Properties, the Contribution of Polyphenols and the Challenges in Deducing Their True Health Benefits

“…Other studies on the impact of digestion, in vitro , on antioxidant capacity/activity and/or total phenolic content reported a decrease in fruit beverages [84], either no change or a decrease for herbal teas, prepared from infusions of powdered herbs [85] or either decreases, increases or no statistically significant change for dietary antioxidant supplements [86]. The type of in vitro model ( i.e.…”