- Red fruits and their juices are rich sources of polyphenols, especially anthocyanins.
Some studies have shown that such polyphenols can inhibit enzymes of the carbohydrate metabolism,
such as α-amylase and α-glucosidase, that indirectly regulate blood sugar levels. The presented
study examined the in vitro inhibitory activity against α-amylase and α-glucosidase of various
phenolic extracts prepared from direct juices, concentrates, and purees of nine different berries which
differ in their anthocyanin and copigment profile. Generally, the extracts with the highest phenolic
content—aronia (67.7 ± 3.2 g GAE/100 g; cyanidin 3-galactoside; chlorogenic acid), pomegranate
(65.7 ± 7.9 g GAE/100 g; cyanidin 3,5-diglucoside; punicalin), and red grape (59.6 ± 2.5 g GAE/100 g;
malvidin 3-glucoside; quercetin 3-glucuronide)—showed also one of the highest inhibitory activities
against α-amylase (326.9 ± 75.8 µg/mL; 789.7 ± 220.9 µg/mL; 646.1 ± 81.8 µg/mL) and α-glucosidase
(115.6 ± 32.5 µg/mL; 127.8 ± 20.1 µg/mL; 160.6 ± 68.4 µg/mL) and, partially, were even more potent
inhibitors than acarbose (441 ± 30 µg/mL; 1439 ± 85 µg/mL). Additionally, the investigation of single
anthocyanins and glycosylated flavonoids demonstrated a structure- and size-dependent inhibitory
activity. In the future in vivo studies are envisaged.
