Arctostaphylos uva-ursi L. leaves extract and its modified cysteine preparation for the management of insulin resistance: chemical analysis and bioactivity

Abstract

Bearberry (Arctostaphylos uva-ursi L.) is a perennial plant of the heather family (Ericaceae). The leaves are dominated by arbutin, phenol carbonic acids flavonoids, saponins, etc. It was previously shown that the bearberry leaves extract reduced blood glucose level in healthy animals under glucose overload, so it need to be studied more detail. The aim of the study was to investigate the chemical composition and the effect of dry alcohol extract from bearberry leaves, which enriched with cysteine, on the rats pancreas under experimental dexamethasone-induced insulin resistance (IR). Arctostaphylos uva-ursi L. leaves extract and its modified cysteine preparation were obtained according to the developed method with 50% ethanol solution. Their phytochemical profile, hypoglycaemic and pancreatic protective effect were investigated. Phenologlycoside (arbutin), phenolic carboxylic acid (gallic acid), 5 flavonoids and 4 hydroxycinnamic acids were identified and quantified in the extracts by HPLC. Present data revealed that bearberry leaves alcoholic dry extract enriched with cysteine has a hypoglycaemic and pancreatic protective effect in treated animals under dexamethasone-induced IR model. Treatment improved hyperglycaemia, insulin resistance and beta cell reduction induced by dexamethasone injections.

Keywords: Arctostaphylos uva-ursi L.; Extract; Hypoglycaemic activity; Leaves; Phenolic substances.

Fig. 1

Typical chromatograms of the bearberry extract (PE50)

Fig. 2

a Body weight dynamics, grams (ordinate axis) per weeks (abscissa axis). b Pancreas weight, grams. c Pancreatic weight relative to body weight, %. Each value represents the mean ± standard error of (n = 6). *indicates significant difference relative to IC group (p ≤ 0.05). #indicates significant difference relative to Dex group (p ≤ 0.05)

Fig. 3

Photomicrograph of rat pancreas, H&E. A Normal size distribution of pancreatic islets (× 100). B Pancreatic acini and pancreatic beta cells are not changed (× 250). C Increased number of small pancreatic islets (× 100). D Very large pancreatic island (× 200). E Increase of the pancreatic islands average size (× 100). F Normalization of beta cells in the islet (× 200). G Increase in the pancreatic island size (× 100). H The pancreatic islands state reparation (× 200). I Visual restoration of the pancreatic islets number (× 100). J Some nuclear hypertrophy and beta cells cytoplasm vacuolation (× 250). K Unchanged pancreatic islet (× 200). L Vacuolation of beta cells and some devastation of the pancreatic island (× 200). Scale bar: 100 µm