In vitro α-amylase and α-glucosidase Inhibitory Activities of Coccinia grandis Aqueous Leaf and Stem Extracts

The role of selected nutraceuticals in management of prediabetes and diabetes: An updated review of the literature. Part II

We have already published a review about the results of clinical trials evaluating the effects of selected nutraceuticals on glycemia in humans. In this second part, we describe the role of other nutraceuticals involved in dysglycemia. The available evidence showed promising hypoglycemic effects of the nutraceuticals reviewed both for their efficacy and safety profile. However, contradictory results as regard the efficacy of some supplements such as Allium sativum, Juglans regia, and Lycium barbarum on glucose homeostasis have emerged from some clinical studies. Other nutraceuticals including Aloe vera, Amorphophallus Konjac, Bauhinia forficata, Coccinia, Ganoderma lucidum, Ipomoea batatas, and Lupinus mutabilis require larger and long-term studies rigorously designed to confirm their hypoglycemic effects due to the scarce data available and the poor quality of clinical trials. Further studies are also required for Cinnamomum, Cynara scolymus, Momordica charantia, Olea europaea, and Opuntia streptacantha. Moreover, well-designed large and long-term clinical trials including the use of standardized nutraceutical preparations are necessary for Phaseolus vulgaris and Vaccinium myrtillus.

In vitro α-glucosidase inhibitory activity of Tamarix nilotica shoot extracts and fractions

α-glucosidase inhibitors represent an important class of type 2 antidiabetic drugs and they act by lowering postprandial hyperglycemia. Today, only three synthetic inhibitors exist on the market, and there is a need for novel, natural and more efficient molecules exhibiting this activity. In this study, we investigated the ability of Tamarix nilotica ethanolic and aqueous shoot extracts, as well as methanolic fractions prepared from aqueous crude extracts to inhibit α-glucosidase. Both, 50% ethanol and aqueous extracts inhibited α-glucosidase in a concentration-dependent manner, with IC₅₀ values of 12.5 μg/mL and 24.8 μg/mL, respectively. Importantly, α-glucosidase inhibitory activity observed in the T. nilotica crude extracts was considerably higher than pure acarbose (IC₅₀ = 151.1 μg/mL), the most highly prescribed α-glucosidase inhibitor on the market. When T. nilotica crude extracts were fractionated using methanol, enhanced α-glucosidase inhibitory activity was observed in general, with the highest observed α-glucosidase inhibitory activity in the 30% methanol fraction (IC₅₀ = 5.21 μg/mL). Kinetic studies further revealed a competitive reversible mechanism of inhibition by the plant extract. The phytochemical profiles of 50% ethanol extracts, aqueous extracts, and the methanolic fractions were investigated and compared using a metabolomics approach. Statistical analysis revealed significant differences in the contents of the crude extracts and fractions and potentially identified the molecules that were most responsible for these observed variations. Higher α-glucosidase inhibitory activity was associated with an enrichment of terpenoids, fatty acids, and flavonoids. Among the identified molecules, active compounds with known α-glucosidase inhibitory activity were detected, including unsaturated fatty acids, triterpenoids, and flavonoid glycosides. These results put forward T. nilotica as a therapeutic plant for type 2 diabetes and a source of α-glucosidase inhibitors.

Efficacy and safety of a herbal drug of Coccinia grandis (Linn.) Voigt in patients with type 2 diabetes mellitus: A double blind randomized placebo controlled clinical trial

BACKGROUND

Several lines of preclinical studies have shown promising antidiabetic effects of the aqueous leaves extract of Coccinia grandis (Linn.) Voigt (Cucurbitaceae) in vivo and in vitro.

PURPOSE

The present study was conducted to evaluate the efficacy and safety of a newly developed herbal formulation of C. grandis in newly diagnosed patients with type 2 diabetes mellitus (T2DM).

STUDY DESIGN

A three months long, randomized, double blind, placebo controlled clinical trial in patients with newly diagnosed T2DM.

METHOD

Based on fasting plasma glucose (FPG) concentration, a total number of 158 newly diagnosed patients with T2DM (45 ± 15 years age) were recruited for the present trial from the University Medical Clinic, Teaching Hospital, Karapitiya, Galle, Sri Lanka. They were randomly assigned to the test or placebo group to receive 500 mg of herbal drug (n = 79) or placebo drug (n = 79) once daily for three months. Patients and investigators were blinded for the treatment. Percentage of glycated hemoglobin (HbA_1C %), insulin and lipid profile parameters were estimated at the base line and at the end of the intervention. Serum concentration of fructosamine was assessed at every other visit of the trial. The homeostatic model assessment for insulin resistance (HOMA-IR), atherogenic index (AI), cardio-protective index (CPI) and coronary risk index (CRI) were calculated. Furthermore, fasting plasma glucose concentration, renal and liver toxicity parameters, hematological parameters, blood pressure (BP) were assessed throughout the study in two weekly intervals till the end of three months.

RESULTS

Out of 158, a total number of 145 patients completed the entire clinical trial period successfully. Mean (SD) changes of variables from the baseline to the end of the intervention in test and placebo groups were 0.65 (0.54) and 0.08 (0.66) for HbA_1C % (p < 0.001), 1.91 (3.07) and -1.28 (9.77) for insulin (p < 0.001), 0.02 (0.03) and -0.01 (0.04) for frucosamine (p < 0.001), 1.51 (0.49) and 0.05 (0.50) for FPG (p < 0.001), 1.73 (1.36) and -0.37 (3.38) for HOMA-IR (p < 0.001), 0.16 (0.18) and -0.04 (0.42) for TG (p < 0.001), 0.07 (0.08) and -0.02 (0.19) for VLDL-C (p < 0.001), respectively. However, the herbal drug of C. grandis was unable to change other outcome variables significantly when compared to the placebo (p > 0.05). All the renal, liver and toxicity parameters, hematological parameters and BP were within the normal physiological reference ranges at each visit.

CONCLUSION

Treatment with herbal drug of C. grandis (500 mg per day) for three months for patients with newly diagnosed T2DM significantly improved their glycemic and selected lipid profile parameters with well tolerated safety.

LC-QTOF-MS-based metabolite profiling and evaluation of α-glucosidase inhibitory kinetics of Coccinia grandis fruit

Coccinia grandis is an important food crop of the Cucurbitaceae family, widely used for culinary purposes in India. It is reported to possess hypoglycemic, hypolipidemic and antioxidant activities. The current study was aimed to explore the inhibition kinetics as well as major constituents of the active fraction of C. grandis against α-glucosidase. The kinetic study was performed through spectrophotometric assay, with p-nitrophenyl-α-d-glucopyranoside as a substrate with varying concentrations. An in vitro antioxidant study was performed by DPPH assay. In addition, UPLC-QTOF-MS analysis was carried out for metabolite profiling of the bioactive fraction of C. grandis. The results showed that the difference between the α-glucosidase inhibitory activity of the ethyl acetate fraction of C. grandis (EFCG) (IC₅₀ 2.43 ± 0.27 mg/ml), and standard inhibitor, acarbose (2.08 ± 0.19 mg/ml), was not statistically significant at a P-value of 0.05. The enzyme kinetics confirmed the inhibition mode in a mixed manner. The EFCG also showed the highest antioxidant activity (101.74 ± 1.95 μg/ml) among all of the fractions. A significant correlation between antioxidant and α-glucosidase inhibitory activity of EFCG was observed. The LC-QTOF-MS study of the EFCG putatively identified 35 metabolites, which may be responsible for its antioxidant and α-glucosidase inhibitory properties. Thus, C. grandis fruits can serve as a functional food to address diabetes-related disorders associated with α-glucosidase.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.