Abstract
Medicinal plant extracts are becoming increasingly important as an alternative for traditional drugs against diabetes mellitus (DM). For this reason, we initialized a target-based screening of 111 root extracts from an open access plant extract library (PECKISH) by ascertaining their in-vitro inhibitory efficacy on α-glucosidase. The two most active extracts Geum urbanum L. (roseroot) and Rhodiola rosea L. (avens root) were further tested for their antidiabetic activities in terms of their impact on different regulatory key points of glucose homeostasis. To this end, various enzyme- and cell culture-based in-vitro assays were employed including the determination of sodium-dependent glucose transporter 1 (SGLT1) activity in Caco-2 monolayers by Ussing chambers and of glucose transporter 4 (GLUT4) translocation in a GFP-reporter cell line. Subsequently, the antidiabetic potential of the root extracts were further evaluated in in-vivo models, namely hen’s eggs test and the fruit fly Drosophila melanogaster. Avens root extract was found to be a more potent inhibitor of the enzymes α-glucosidase and dipeptidyl peptidase-4 (DPP4) than roseroot extract. Most importantly, only avens root extract exhibited antidiabetic activity in the two in-vivo models eliciting a reduced blood glucose level in the in-ovo model and a decline of the triglyceride level in a dietary starch-induced D. melanogaster obesity model. Analyses of the polyphenolic composition of the avens root extract by HPLC revealed a high content of ellagic acid and its derivatives as well as ellagitannins such as pedunculagin, stenophyllanin, stachyurin, casuarinin and gemin A. In conclusion, avens root extract represents a promising medicinal plant that should be considered in further in-vivo studies on hyperglycemia in laboratory rodents and humans.
Highlights
Diabetes mellitus (DM) and its consequences have become an increasing health problem worldwide and a considerable financial burden
Of the 111 root samples of the local plant extract collection Kiel in Schleswig-Holstein (PECKISH) extract library that were screened for α-glucosidase inhibition, the aqueous extracts of G. urbanum and R. rosea were found to be most potent and, were selected for further studies. α-Glucosidase activity was inhibited by both extracts in a dose-dependent manner resulting in IC50 values of 3.76 μg/ml for avens root and 5.51 μg/ml for roseroot
Roseroot extract at a final concentration of 300 μg/ml led to an efficient inhibition of α-amylase activity by 90.4%, which is comparable to the effect of the reference inhibitor acarbose (89.0% inhibition at the same concentration)
Summary
Diabetes mellitus (DM) and its consequences have become an increasing health problem worldwide and a considerable financial burden. Modulation of the blood glucose level can be achieved by targeting various hormones, enzymes and transporters along the carbohydrate digestion/ absorption pathway including intestinal α-amylase, α-glucosidase, sodium-dependent glucose transporter 1 (SGLT1) as well as the insulin secretion machinery or glucose transporter 4 (GLUT4) in peripheral tissues (Padhi et al, 2020). In this regard, studies, which systematically investigate whether plant extracts act on more than one of these targets, are of interest. More studies are needed to 1) evaluate known traditional medicinal plants, 2) identify novel plant material with antidiabetic properties, 3) elucidate the underlying molecular mechanisms of action and 4) characterize the biologically active compounds
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