The glycemic index of pigmented potatoes is related to their polyphenol content

Abstract

Polyphenol extracts from coloured fruits and vegetables inhibit α-glucosidase in vitro, however it is not known whether this translates into an attenuation of blood glucose response in vivo. We examined this relationship in a GI study by feeding coloured potatoes to 9 healthy volunteers. We also examined the in vitro inhibitory activity of potato anthocyanin extracts on rat intestinal α-glucosidase. Potatoes (Purple Majesty; Red-Y38; Yukon Gold and Snowden) were fed with skin after cooking in a convection oven, using a random block design and 50 g available carbohydrate. Glucose was used as the standard and venous blood collected at 0, 15, 30, 45, 60, 90, 120 min. Areas under the curve (AUC) for glucose and insulin were calculated, and GI and Insulin Index derived. Neither AUC for blood glucose response nor insulin was significantly different among the various potatoes studied. Although the mean GI (±SE) values for the potato types varied (purple = 77.0 ± 9.0; red = 78.0 ± 14.0; yellow = 81.0 ± 16.0; and white = 93.0 ± 17.0), these differences were not significantly different. The mean (±SE) polyphenol content (mg GAE/100 g DW) was 234 ± 28; 190 ± 15; 108 ± 39; 82 ± 1 for purple, red, yellow and white potatoes, respectively. There was a significant inverse correlation between polyphenol content and GI of the potatoes (r = -0.825; p < 0.05; n = 4). In vitro, polyphenol extracts of red and purple potatoes inhibited α-glucosidase by 37.4 ± 2.2% and 28.7 ± 3.2%, respectively. The GI of coloured potatoes is significantly related to their polyphenol content, possibly mediated through an inhibitory effect of anthocyanins on intestinal α-glucosidase.

Potatoes and risk of chronic disease: a systematic review and dose–response meta-analysis

“…Thus, potatoes contain additional constituents that may affect the utilization of starch in the human organism, e.g. varieties rich in polyphenols have been demonstrated to inhibit the catalytic cleavage of starch in the small intestine [58,59], and an inverse association between potato phenol content and GI has been found [60]. Moreover, deep frying is a form of preparation that can significantly increase the fat content of the meal which may consecutively promote the onset of overweight, obesity, and T2D [15,61].…”

Inhibitory Effects of Siegesbeckia orientalis Extracts on Advanced Glycation End Product Formation and Key Enzymes Related to Metabolic Syndrome

“…Several studies have reported that natural polyphenols could inhibit pancreatic lipase [ 18 , 57 , 58 ]. Table 1 demonstrates that the inhibitory effects on lipase of S. orientalis extracts correlated well with TPC, TFC, DPPH scavenging activity, reducing power, suppression of dicarbonyl compounds formation, and the inhibition activity on α-glucosidase (R = 0.813–0.985).…”

UF-LC-DAD-MS n for discovering enzyme inhibitors for nutraceuticals and functional foods

“…α-Glucosidase is an enzyme present in the brush border of the small Li et al UF-LC-DAD-MS n for discovering enzyme inhibitors intestine, whose inhibitors act by a reversible inhibition, could delay the absorption of carbohydrates from the small intestine, and suppress the postprandial blood glucose and insulin levels . Recent studies in the discovery of food and other natural sources of α-glucosidase inhibitors have attracted considerable interest as α-glucosidase is an important biomarker for treating type 2 diabetes mellitus (Li et al, 2009;Ramdath et al, 2014;Tang et al, 2016;Zhou et al, 2012;Zhang et al, 2015). The fruit of hawthorn (Crataegus oxyacantha L.) has been part of foods or confectionaries in different cultures, however hawthorn tree leaves also contained flavonoids that were α-glucosidase inhibitors in a UF-LC-MS n screening study (Li et al, 2009).…”

“…(Table 3). These polyphe-nols are commonly found in fruits, vegetables, cereals and pulse grains, thus consumption of these foods are beneficial to blood glucose management Ramdath et al, 2014;Tang et al, 2016;Zhou et al, 2012;Zhang et al, 2015). UF-LC-MS n was used to rapidly and selectively screen and identify major α-glucosidase ligands or inhibitors in Radix Astragali and polyphenols particularly calycosin, formononetin and other isoflavones were found to be strong α-glucosidase inhibitors.…”