Dose-response efficacy of mulberry fruit extract for reducing post-prandial blood glucose and insulin responses: randomised trial evidence in healthy adults.

Extracts of mulberry have been shown to reduce post-prandial glucose (PPG) and insulin (PPI) responses, but reliability of these effects and required doses and specifications are unclear. We previously found that 1·5 g of a specified mulberry fruit extract (MFE) significantly reduced PPG and PPI responses to 50 g carbohydrate as rice porridge, with no indications of intolerance. The trials reported here aimed to replicate that work and assess the efficacy of lower MFE doses, using boiled rice as the carbohydrate source. Two separate randomised controlled intervention studies were carried out with healthy Indian males and females aged 20-50 years (n 84 per trial), with PPG area under the curve over 2 h as the primary outcome. Trial 1 used doses of 0, 0·37, 0·75, 1·12 and 1·5 g MFE in boiled rice and 0 or 1·5 g MFE in rice porridge. Trial 2 used doses of 0, 0·04, 0·12, 0·37 g MFE in boiled rice. In trial 1, relative to control, all MFE doses significantly decreased PPG (-27·2 to -22·9 %; all P ≤ 0·02) and PPI (-34·6 to -14·0 %, all P < 0·01). Breath hydrogen was significantly increased only at 1·5 g MFE (in rice porridge), and self-reported gastrointestinal symptoms were uniformly low. In trial 2, only 0·37 g MFE significantly affected PPG (-20·4 %, P = 0·002) and PPI (-17·0 %, P < 0·001). Together, these trials show that MFE in doses as low as 0·37 g can reliably reduce PPG and PPI responses to a carbohydrate-rich meal, with no apparent adverse effects.

HPLC-FLD determination of NBD-cholesterol, its ester and other metabolites in cellular lipid extracts.

22-[N(-7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-23,24-bisnor-5-cholen-3ß-ol (NBD-cholesterol), a fluorescent cholesterol analog, was an extragenous cholesterol tracer used to study cholesterol absorption and metabolism in cultured cells. In order to measure free intracellular cholesterol and its esters, a precise and sensitive method employing high-performance liquid chromatography/fluorescence detection (HPLC-FLD) was developed for the first time. Method validation showed a limit of detection at 30 ng/mL. The calibration curve was linear within the range of 0.0625-10.0 µg/mL (r(2) = 0.999). Accuracy and precision were highlighted by good recovery and low variations. Apart from NBD-cholesteryl oleate, two additional cellular metabolites of NBD-cholesterol, probably an isomer and an oxidation product, were determined in the lipid extracts of Caco-2 human colon adenocarcinoma cells according to mass spectrometry. In AC29 mouse malignant mesothelioma cells overexpressing acyl-CoA:cholesterol acyltransferase-1 (ACAT1) or ACAT2, only the oxidized metabolite was detected. Using the newly developed method, YIC-C8-434, a known ACAT inhibitor, was shown to inhibit ACAT activity in Caco-2 cells, as well as in AC29/ACAT1 or AC29/ACAT2 cells. In conclusion, the sensitive and specific HPLC-FLD method is a powerful tool for simultaneous quantification of intracellular NBD-cholesterol and its oleoyl-ester.