Antidiabetic and antihypertensive effect of a polyphenol-rich fraction of Thymelaea hirsuta L. in a model of neonatal streptozotocin-diabetic and N(G) -nitro-l-arginine methyl ester-hypertensive rats.

BACKGROUND: The present study examined the effect of the polyphenol-rich fraction from Thymelaea hirsuta (PRF-Th) in a rat model of streptozotocin (STZ)-diabetes and nitric oxide (NO)-deficient hypertension. METHODS: Diabetes was induced by a single dose of STZ (90 mg/kg, i.p.). To induce NO-deficient hypertension, rats were treated with the NO synthase inhibitor N(G) -nitro-l-arginine methyl ester; l-NAME; 30 mg/kg per day, p.o. for 3 weeks. The effects of 21 days treatment with 80 mg/kg per day PRF-Th in the drinking water were evaluated in diabetic-hypertensive (DH) rats. In all groups (n = 6 in each), glycemia and systolic blood pressure were determined weekly. At the end of the experiment, hepatic glycogen was determined. RESULTS: Blood glucose levels decreased gradually from baseline until the end of the experiment in untreated DH rats (from 1.92 ± 0.09 to 1.3 ± 0.1 g/L; P < 0.05). Administration of PRF-Th concomitantly with l-NAME prevented the blood pressure increase in rats. After 21 days, blood pressure in PRF-Th + l-NAME- and l-NAME-treated rats was 132 ± 1 and 157 ± 1 mmHg, respectively (P < 0.001). Administration of 2 mL/kg per day PRF-Th to DH rats significantly increased hepatic glycogen levels compared with levels in untreated DH rats (13.65 ± 1.84 vs 6.34 ± 0.75 mg/g tissue, respectively; P < 0.01). Moreover, PRF-Th significantly reduced the amount of glucose absorbed in in situ perfused jejunum segments compared with control (by 33.6%; P <0.001). This effect of PRF-Th was comparable with that of acarbose, an α-glucosidase inhibitor. CONCLUSIONS: The findings of the present study indicate that T. hirsuta has antidiabetic and antihypertensive activity in STZ-diabetic, NO-deficient hypertensive rats. This effect seems to be due to its rich polyphenol content. Therefore, T. hirsuta may be useful as a food supplement for the prevention of type 2 diabetes and hypertension.

Antidiabetic medicinal plants as a source of alpha glucosidase inhibitors.

The aim of this study is to collate all available data on antidiabetic plants that inhibit alpha glucosidase, reported mainly by Medline (PubMed) these last years. In the present study, interest is focused on experimental researches conducted on hypoglycemic plants particularly those which show alpha glucosidase inhibitor activity alongside bioactive components. This study describes 47 species that belong to 29 families. The plant families, which enclose the species, studied most as inhibitors of alphaglucosidase, are Fabaceae (6 species.), Crassulaceae (3 species), Hippocrateacaea (3 species), Lamiaceae (3 species), and Myrtaceae (3 species), with most studied species being Salacia reticulata (Hippocrateaceae) and Morus alba (Moraceae). The study also covers natural products (active natural components and crude extracts) isolated from the medicinal plants which inhibit alpha glucosidase as reported this last decade. Many kinds of these isolated natural products show strong activity such as, Alkaloids, stilbenoids (polyphenol), triterpene, acids (chlorogenic acid, betulinic acid, syringic acid, vanillic acid, bartogenic acid, oleanolic acid, dehydrotrametenolic acid, corosolic acid, ellagic acid, ursolic acid, gallic acid), phytosterol, myoinositol, flavonoids, Flavonolignans, anthraquinones, anthrones, and xanthones, Feruloylglucosides, flavanone glucosides, acetophenone glucosides, glucopyranoside derivatives, genine derivatives, flavonol, anthocyanin and others.