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.

The antihyperglycemic effect of T. hirsuta can be explained, in part, by the inhibition of intestinal α-glucosidase and intestinal glucose absorption.

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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.

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.