Title : In vitro study of inhibitory effects of guelder rose fruit phenolics on digestive enzymes
Obesity is a multifactorial disease affected by behavioural, genetic and environmental factors and is a major worldwide threat. It is considered to be a risk factor associated with the genesis or development of diabetes. One of the most important strategies in the treatment or prevention of these disorders is the development of natural inhibitors of digestive enzymes that interfere with the hydrolysis and absorption of dietary carbohydrates and lipids. Pancreatic lipase, α-glucosidase and α-amylase are the major enzymes involved in the hydrolysis of these nutrients. Fruits are a source of natural inhibitors of hydrolysing enzymes and their inhibitory effect is associated with phenolic compounds.
Viburnum opulus L. (Adoxaceae), commonly known as guelder rose, is widespread in Europe, North and Central Asia, and North America. Guelder rose is valuable decorative, medicinal and food plant. The V. opulus fruits and fruit juice have been used to treat a wide range of illnesses, including bleeding, heart disease, high blood pressure, coughs and cold, gastrointestinal mucosa damage, kidney stones, neurosis and diabetes.
In this study, the inhibition of α-amylase, α-glucosidase and pancreatic lipase of components from V. opulus fruits was examined, including the type of inhibition and possible interaction with commercial inhibitors of these enzymes. Additionally, the qualitative and quantitative composition of the purified phenolic extract (PPE) was determined using UPLC/MS/MS method. PPE was obtained from crude acetone extract using solid phase extraction on Sep-Pac C18 column.
The results obtained show that PPE from V. opulus fruit has the ability to inhibit the activity of the enzymes tested in a dose-dependent manner. IC50 value of purified guelder rose fruit extract was 61,51 µg/mL for α-amylase in presence of potato starch as a substrate. In the case of α-glucosidase inhibition, two substrates were used: maltose and sucrose, for which the substrate concentration needed to inhibit the enzyme by half was respectively: 149,86 and 317,32 µg/mL. While, PPE extract in the amount of 3.29 mg/mL decreased activity of pancreatic lipase by 50%. Hydroxycinnamic acids were the main phenolics in PPE, followed by flavanols and flavonols. Chlorogenic acid was present at the highest amount and constituted about 65% of the sum of all identified phenolic compounds. The tested extract also exhibited synergistic effects with commercial inhibitors of glycolytic enzymes and pancreatic lipase, such as acarbose and orlistat, respectively.
The research was financed under the financial support of the Polish National Science Centre (project nr 2016/23/B/NZ9/03629).