Impact of the New Zealand pine bark extract (Enzogenol®) on sucrose metabolism and glycaemic responses in healthy adults – a single-blind, randomised, placebo-controlled, crossover trial

This is an acute, randomised, single-blind, crossover, placebo-controlled study. The study aims to determine the effects of the New Zealand pine bark extract (Enzogenol®) in two effective doses (50 and 400 mg) in improving glycaemic and insulinaemic postprandial responses in healthy participants when co-administered with 75 g of sucrose solution. There will be a total of four visits involving the following intervention arms: placebo (only 75 g of sucrose powder), 250 mg of Reducose®, 50 mg of Enzogenol®, and 400 mg of Enzogenol®. Each intervention extract will be added with 75 g of sucrose powder, well mixed with 250 mL of water in an opaque vessel (to conceal contents) given to participants on separate occasion during the study visits. All intervention arms will be of similar taste and odour. Enzogenol® will be compared with Reducose® regarding its efficacy and impact on glycaemia. Briefly, Reducose® (Phynova Group, Ltd.) is a commercially available water extract of white mulberry (Morus alba Linn) leaf extract (standardised to 4.5-5.5% 1- deoxynojirimycin, DNJ, a type of iminosugar). DNJ has been demonstrated in research to inhibit carbohydrate-digesting enzymes such as alpha-glucosidase and amylase due to its structure similarity to carbohydrate monosaccharides. They potentially compete with carbohydrates for the enzyme receptors that may lead to the delay or reduction in carbohydrate digestion. At each study visit, all eligible participants will be checked for dietary and lifestyle compliance, such as having fasted at least 10-12 hours prior to the visit, keeping their diet constant, no strenuous physical activity, no alcohol, no caffeinated tea or coffee formulations, no health supplements 24 hours to visit, and no consumption of pine bark or mulberry leaf extract throughout the duration of the study. A baseline sample will be taken at 10 min and at 0 min prior to consuming the treatment at each visit. The participants will be required to consume the treatment within 5 minutes. Further blood samples will be taken at time points 15, 30, 45, 60, 90 and 120 min. Blood samples are obtained via the finger prick test using a single use disposable lancet (Accu-Chek Safe T-Pro Plus) and 300 uL blood collected into chilled microvette capillary blood collection tubes treated with heparin (Sarstedt Microvette CB300 Lithium Heparin) for plasma insulin analysis. Samples are centrifuged to obtain 200 uL supernatent for plasma insulin analysis. Plasma glucose levels obtained from the finger prick test are immediately measured using a glucose meter (MediSense, Optium, Abbott, 2.7-4.0% CV). There is a washout period of at least a week between study visits.