Coronavirus Disease 2019 (COVID-19) has become a major health problem causing severe acute respiratory illness in humans. It has spread rapidly around the globe since its first identification in Wuhan, China, in December 2019. The causative virus is called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the World Health Organization (WHO) named the new epidemic disease Coronavirus Disease (COVID-19). The incidence of COVID-19 continues to increase with more than three million confirmed cases and over 244,000 deaths worldwide. There is currently no specific treatment or vaccine against COVID-19. Therefore, in the absence of pharmaceutical interventions, the implementation of precautions and hygienic measures will be essential to control and to minimize human transmission of the virus. In this review, we highlight the epidemiology, transmission, symptoms, and treatment of this disease, as well as future strategies to manage the spread of this fatal coronavirus.

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.

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Many cardiovascular diseases such as arterial hypertension are associated with an increase in blood platelet activity. Arbutus unedo (Ericaceae) is a medicinal plant reputed to treat arterial hypertension, so the present study was undertaken in order to determine the antiaggregant effect. The crude aqueous extract showed an inhibition of thrombin-induced platelet aggregation (IC50 = 1.8 +/- 0.09 g/L, n = 10). The subsequent extraction of Arbutus unedo leaves by successive solvents showed that the methanol and ethyl acetate extracts accounted for most of the antiaggregant activity (IC50 = 0.7 +/- 0.08, n = 9; 0.6 +/- 0.05; n = 9, respectively). The tannins isolated from the methanol extract exhibited a strong antiplatelet effect (% of inhibition = 75.3 +/- 1.4, n = 8) and may be the major chemical compounds responsible for this action. Our results support the traditional use of this plant in the preventive or therapeutic treatment of platelet aggregation linked to arterial hypertension.

Arbutus unedo L. (Ericaceae) is used in oriental Morocco to treat arterial hypertension. We studied its vasodilator effect and mechanisms of action in vitro. The root aqueous extract of Arbutus (0.25 mg/mL) produced a relaxation of noradrenaline-precontracted ring preparations of rat aorta with intact endothelium. Relaxation by Arbutus did not occur in specimens without endothelium and was inhibited by pretreatment with 100 microM N(G)-methyl-L-arginine (L-NMA), 10 microM methylene blue or 50 microM 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) but not by 10 microM atropine. These results suggest that Arbutus produces an endothelium-dependent relaxation of the isolated rat aorta which may be mediated mainly by a stimulation of the endothelial nitric oxide synthase by mechanisms other than activation of muscarinic receptors.

Nigella sativa L. (Ranunculaceae), commonly referred to as black seeds or black cumin, is used in popular medicine (herbal) all over the world for the treatment and prevention of several diseases, including diabetes. This study aims to investigate the inhibitory effect of N. sativa extracts and fractions against the activities of intestinal α-glucosidase and pancreatic α-amylase in vitro, and to explain the inhibitory effect of these fractions against these enzymes by identifying their active compounds responsible for this effect and determine their modes of inhibition. To do so, N. sativa hexane and acetone extracts were prepared and analyzed by GC–MS and HPLC–DAD, respectively. The hexane extract was further fractioned into eight different fractions, while the acetone extract generated eleven fractions. The extracts as well as the resulting fractions were characterized and evaluated for their potential in vitro antidiabetic activity using intestinal α-glucosidase and pancreatic α-amylase inhibitory assays in vitro. Hexane extract and fractions were less active than acetone extract and fractions. In the case of intestinal α-glucosidase activity, the acetone fraction SA3 had a high inhibitory effect on intestinal α-glucosidase activity with 72.26 ± 1.42%, comparable to the effect of acarbose (70.90 ± 1.12%). For the pancreatic α-amylase enzymatic inhibitory assay, the acetone fractions showed an inhibitory capacity close to that for acarbose. In particular, the SA2 fraction had an inhibitory effect of 67.70 ± 0.58% and was rich in apigenin and gallic acid. From these fractions, apigenin, (−)-catechin, and gallic acid were further characterized for their inhibitory actions. IC50 and inhibition mode were determined by analyzing enzyme kinetic parameters and by molecular modeling. Interestingly, (−)-catechin showed a possible synergistic effect with acarbose toward α-glucosidase enzyme inhibition, whereas apigenin showed an additive effect with acarbose toward α-amylase enzymatic inhibition. Furthermore, we studied the toxicity of N. sativa hexane and acetone extracts as well as that of acetone fractions. The result of acute toxicity evaluation demonstrated that N. sativa extracts were nontoxic up to a concentration of 10 g/kg, except for fraction SA3. Taken together, these results indicate that N. sativa extracts and/or derived compounds could constitute promising nutraceuticals for the prevention and treatment of type 2 diabetes mellitus.

The goal of the present study is to test the effect of water extract (WE) of four medicinal plants used as antidiabetics in Eastern Morocco (Arbutus unedo: Au, Ammoïdes pusilla: Ap, Thymelaea hirsuta: Th, and Urtica dioïca: Ud). These plants are used in cooking to bring out the flavor in a dish or to complement it. The first experiment was realized in order to determine the antidiabetic effect of the WE of these plants during 5 weeks’ treatment. Seven groups of Wistar rats were used: Healthy controls, neonatal streptozotocin (n-stz) induced-diabetic rats (90 mg/kg; intraperitoneally [i.p.]), n-stz + tolbutamide (400 mg/l), and 4 groups n-stz + WE of plants (400 mg/l, drink water). The percentages of Plasma glucose lowering effect were, respectively for Au, Ap, Th, Ud and tolbutamide: 31.6 % p<0.01, 27.4 % p<0.05, 38.2 % p<0.01, 13 % and 33.9 % p<0.05 when compared with untreated diabetic controls. In a second experiment, oral glucose tolerance tests were carried out in n-stz induced-diabetic rats. The i.p. administration of the water extract (WE) of Ap and Ud (150 mg/kg) 30 minutes before the glucose overload (2 g/kg) showed a significant reduction glycemia, respectively of 36 % at 60 min (p<0.05) and 50 % at 180 min (p<0.05) after glucose overload compared with controls. In contrast, the effect of WE of Au and Th (150 mg/kg, i.p.) was not significant. The in vitro study of glucose utilization by isolated rat hemidiaphragm suggests that these extracts in combination with insulin potentiate its activity and enhance the utilization of glucose. In conclusion, it seems that these plants possess antidiabetic activity.