Antioxidant activity and inhibitory effect of polyphenolic-rich extract from Betonica officinalis and Impatiens noli-tangere herbs on key enzyme linked to type 2 diabetes

• It is the first study on anti-diabetic potential of the Betonica officinalis and Impatiens noli-tangere herbs by the α-amylase and α-glucosidase inhibition.
• Ultrafiltration process was successfully applied for enriched extract in polyphenols and flavonoids compounds.

The aim of this study was to investigate the antioxidant, anti-amylase and anti-glucosidase activities of polyphenolic-rich extracts from Betonica officinalis and Impatiens noli-tangere and to analyze their chemical composition by HPLC–MS. Hydro-alcoholic extracts of the two medicinal herbs were processed by microfiltration and ultrafiltration for concentrating the polyphenolic compounds. Phenolic acid, mainly chlorogenic acid and caffeic acid were the dominant compounds of B. officinalis extracts, while the extracts from I. noli-tangere contain mainly flavonoids, especially isoquercitrin. The polyphenolic-rich extract (retentate UF fraction) from B. officinalis exhibited the most potent DPPH radical scavenging and reducing power activities. The IC50 value of the α-amylase inhibitory effect was 4.20`± 0.30 mg/mL for the B. officinalis polyphenolic-rich extract, slightly higher than that of I. noli-tangere polyphenolic-rich extract of 4.01 ± 0.25 mg/mL. The polyphenolic-rich extract from I. noli-tangere showed remarkable α-glucosidase inhibition activity (IC50 0.47 ± 0.02 mg/mL), compared to the acarbose (IC50 0.38 ± 0.02 mg/mL). However, I. noli-tangere extracts displayed a stronger inhibitory activity than B. officinalis extract fractions. Our study, for the first time, revealed the anti-diabetic potential of the B. officinalis and I. noli-tangere herbs. The results of this study could be helpful to develop medicinal preparations or functional foods for diabetes.

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