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The introduction of glucagon-like peptide 1 (GLP-1)-based therapies has greatly improved the management of type 2 diabetes (T2D), as they ensure good blood glucose control and promote weight loss. Ingestion of standardized herbal remedies that promote the same endogenous metabolic processes affected by the GLP-1-based treatments could provide cheaper alternatives in low- and middle-income countries, where there is currently an increase in the incidence of T2D. The focus in this study was to determine quality control parameters and the prime factors for the Rauvolfia-Citrus tea (RC-tea), as used in Nigerian traditional medicine to treat T2D. We have previously shown that the RC-tea that is made by boiling leaves of Rauvolfia vomitoria Afzel. and fruits of Citrus aurantium L. causes normalization of blood glucose and reduction of ectopic lipid accumulation in genetic diabetic (BKS- db) mice and in humans with T2D. The standardized RC-tea was made by boiling 40 g dried R. vomitoria foliage and 200 g fresh C. aurantium fruits per litre. The resulting golden-brown extract is free of microbial contamination, has pH 5 and contains ca. 230 mg naringin (marker compound for C. aurantium) and 25 mg robinin (marker compound for R. vomitoria) per litre. In addition, the herbal extract has the characteristic HPLC-DAD fingerprint where the marker compounds, naringin and robinin have retention times of approximately 26.3 min and 26.9 min, respectively, when using the outlined column and gradient elution conditions. Comparative evaluations of the antidiabetic effects of the standardized RC-tea and boiling water-extracts made with C. aurantium fruits alone (CA), R. vomitoria foliage alone (RV) and a combination of CA and RV, (CA + RV) in BKS- db mice, indicate that components from R. vomitoria foliage drive the reductions in ectopic lipid accumulation, since CA-treated mice lacked this effect. However, the normalization of blood glucose arises from combination of components from the two source plant materials as administration of either CA or RV resulted in hypoglycaemia. Interestingly, treatment with the CA + RV mixture, generated by mixing individually produced CA and RV plant extracts, resulted in hyperglycaemia, possibly due to drug-drug interactions of the blood glucose-reducing components in either plant extract. Hence, our data show that the best antidiabetic outcome results from the traditional practice of boiling R. vomitoria foliage and C. aurantium fruits together. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Aim of the study: The aim of this randomized and double blinded pilot clinical trial was to investigate the anti-diabetic efficacy of the Rauvolfia-Citrus (RC) tea in humans. We have earlier shown that a combination of calorie-restriction and chronic administration of the RC tea to the genetic diabetic (BKS-db) mice resulted in the normalization of blood sugar, reduction in lipid accumulated in the mice eyes and prevention of the degeneration of the otherwise brittle BKS-db pancreas. The tea is made by boiling foliage of Rauvolfia vomitoria and fruits of Citrus aurantium and is used to treat diabetes in Nigerian folk medicine. Materials and methods: The RC tea was produced using the Nigerian traditional recipe and tested in the traditional dosage on 23 Danish type 2 diabetes (T2D) patients. The participants were divided into two equivalent groups after stratification by sex, age and BMI, in a 4-month double-blinded, placebo-controlled and randomized clinical trial. Most of the study subjects (19/23) were using oral anti-diabetic agents (OADs). Mean disease duration was 6±4.6 years, mean age was 64±7 years and mean BMI was 28.7±3.8kg/m2. Prior to starting the treatment, the participants received individual dietician consultations. Results: At the end of the 4-month treatment period, the treated group showed an 11% decrease in 2-h postprandial plasma glucose relative to the 3% increase in the placebo group (p =0.004). The improvement in blood glucose clearance with RC tea treatment was reflected in a 6% reduction in HbA1c (p =0.02) and in a 10% reduction in fasting plasma glucose (p =0.02), when comparing the post 4-month treatment to pre-treatment baseline values. Though the basal levels of phosphorylated acetyl CoA carboxylase enzyme in skeletal muscle were significantly reduced in the treated group (p =0.04), as compared to the placebo, only the pattern of reductions in the tissue fatty acids (FAs) differed in the two groups. While all types of FAs were reduced in placebo, only saturated (SFA) and monounsaturated (MUFA) FAs were reduced with treatment. Interestingly, a modest increase in the polyunsaturated FAs fraction was observed in the RC treated group. In addition, the reduction in SFA and MUFA with RC tea treatment came solely from the triglyceride fractions, as there was an increase in the skeletal muscle phospholipids. Conclusions: Chronic administration of the RC tea to overweight T2D on OADs caused significant improvements in markers of glycaemic control and modifications to the fatty acid profile of skeletal muscle, without adverse effects or hypoglycaemia. Further exploration of the anti-diabetic effects of the RC tea is warranted. [Copyright &y& Elsevier]