A Review on Experimental Models to Test Medicinal Plants on Postprandial Blood Glucose in Diabetes.

Due to the gravity of postprandial hyperglycemia in the development of microvascular and macrovascular diseases in diabetics, many medicinal plants are tested to determine their effectiveness in glycemic control and the mechanisms of action of the products. Consequently, various diabetic models have been developed and enhanced over the years. The objective of this review is to describe some of the experimental models to study the effect of medicinal plants used to control postprandial hyperglycemia. Data was collected from PubMed, ScienceDirect, Scopus, and Google scholar (1953-2021). Fiftyseven (57) studies were included in this review article. Ten models were identified and described. For each model, we described the targets involved and their roles in postprandial blood glucose control. The experimental design and procedures described the targets such as an α-glucosidase enzyme, SGLT1, GLUT2, DPP-IV, Na+/K+ ATPase pump, or intestinal motility in the models, experiment design and procedures were described. This review will facilitate the selection of the most appropriate model for studying agents used to investigate postprandial blood glucose.

Development of a Thin-Layer Chromatography-Enzymatic Test Combination Method for the Isolation of α-Glucosidase Inhibitors From Thymelaea hirsuta.

A rapid, easy and simple method for the isolation and purification of α-glucosidase inhibitors of the ethyl acetate extract of Thymelaea hirsuta (EaTh) by a combination of thin layer chromatography (TLC) and enzymatic test has been developed. EaTh was demonstrated previously a potent α-glucosidase inhibitory effect. In this study, we developed a simple TLC-enzymatic test (TLC/EZ) combination to isolate α-glucosidase inhibitors present in EaTh.EaTh was extracted by Soxhlet from Thymelaea hirsuta (T. hirsuta). The EaTh was separated on a silica gel column and then on a TLC plate. After TLC separation, the TLC/EZ combination method was applied. α-glucosidase inhibitors were detected directly in the TLC plate using the glucose oxidase peroxidase method (GOD-POD). A good detection of active compounds was obtained in the TLC favoring the TLC/EZ method. Active compounds were then characterized using high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. The main α-glucosidase inhibitors present in EaTh have a molecular ion [M + H]+ at m/z = 543. This proposed method is suitable for a reliable isolation and purification of α-glucosidase inhibitors present in EaTh. It could be proposed as an interesting alternative of the classical method for the isolation and purification of α-glucosidase inhibitors in plant extracts.

Beneficial Effect of Thymelaea hirsuta on Pancreatic Islet Degeneration, Renal Fibrosis, and Liver Damages as Demonstrated in Streptozotocin-Induced Diabetic Rat.

OBJECTIVE: In Morocco, Thymelaea hirsuta (T. hirsuta) (Thymelaeacea) is a medicinal plant widely used to treat and prevent diabetes. The present study aimed to evaluate the medium-term antidiabetic effect of aqueous extract (AqTh) and ethyl acetate fraction (EaTh) of Th and to investigate their putative protective effect on pancreatic islet degeneration, diabetic nephropathy, and liver damages in streptozotocin (STZ)-diabetic rats. METHODS: Experimental diabetes in rats was induced by a single intraperitoneal injection of 50 mg/kg of STZ. During the treatment period (4 weeks), 200 mg/kg AqTh and 50 mg/kg EaTh were orally administrated daily to STZ-diabetic rats. A group of parameters including fasting blood glucose, biochemical parameters, and intestinal α-glucosidase inhibition were studied. Furthermore, histological study of the pancreas, kidney, liver, and aorta was also realized. RESULTS: At the end of the treatment, both AqTh and EaTh had normalized fasting blood glucose to 1.08 and 1.25 g/l, respectively. AqTh has also reduced urinary creatinine and HbAc1. The EaTh showed inhibitory activity against intestinal α-glucosidase, whereas AqTh did not have this inhibitory effect. Furthermore, pancreas hematoxylin and eosin staining showed that AqTh or EaTh prevents pancreatic islet cell degeneration. As the same kidney, Masson's trichrome staining has shown a significant prevention of renal fibrosis in AqTh- or EaTh-treated diabetic rats. On the other hand, liver hematoxylin and eosin staining showed that AqTh and EaTh prevent liver damage. CONCLUSION: We conclude that medium-term administration of AqTh and EaTh exerts significant antihyperglycemic effect in STZ-diabetic rats possibly through intestinal α-glucosidase inhibition and protection against pancreatic islet cell damage. Moreover, AqTh and EaTh treatment prevent nephropathy and liver complications in STZ-diabetic rats.

Inhibition of α-glucosidase and glucose intestinal absorption by Thymelaea hirsuta fractions.

BACKGROUND: Thymelaea hirsuta (L.) Endl. (Thymelaeaceae) is a medicinal plant used in Morocco to treat diabetes. In previous studies T. hirsuta has shown a potent antihyperglycemic effect. Our aim was to study the effect of the plant on α-glucosidase inhibition and intestinal glucose absorption. METHODS: Five fractions of T. hirsuta were tested, in vitro, in vivo and, in situ, to elucidate the inhibition of α-glucosidase and intestinal glucose uptake. RESULTS: The fractions induced, in vitro, a significant inhibition of α-glucosidase. The ethyl acetate fraction (EATh) had high activity and its inhibition mode was non-competitive. The EATh at 50 and 100 mg/kg doses, decreased significantly, in vivo, the postprandial hyperglycemia after sucrose loading in normal and diabetic mice. Moreover, 50 mg/kg of EATh significantly decreased intestinal glucose uptake, in situ, in rats. CONCLUSION: The antihyperglycemic effect of T. hirsuta can be explained, in part, by the inhibition of intestinal α-glucosidase and intestinal glucose absorption.

Antidiabetic oils.

Many studies have demonstrated evidence of the health benefits of natural products. Plant extracts have been tested on a variety of physiological disorders, including diabetes mellitus. Studies have tested aqueous extracts, plant fractions extracts, families of active of compounds, and specific active compounds. In this review, we describe the antidiabetic effects of vegetable oils. Information was collected from ScienceDirect and PubMed databases using the following key words: Diabetes mellitus, Oils, Vegetable oils, Type 1 diabetes, type 2 diabetes, antidiabetic effect, antihyperglycemic, antidiabetic oil. We have compiled approximately ten vegetable oils with including experimental studies that have demonstrated benefits on diabetes mellitus. There are soybean, argan, olive, palm, walnut, black cumin, safflower, Colocynth, Black seed, Rice bran, Cinnamom, and Rocket oils. For each vegetable oil, we investigated on the plant's traditional uses, their pharmacological activities and their antidiabetic effects. It seems that many vegetable oils are really interesting and can be used in the improvement of human health, particularly, to prevent or to treat diabetes mellitus complications.