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Guava (Psidium guajava) Fruit Extract Prepared by Supercritical CO2 Extraction Inhibits Intestinal Glucose Resorption in a Double-Blind, Randomized Clinical Study

1
University of Applied Sciences Upper Austria, 4600 Wels, Austria
2
Austrian Competence Center for Feed and Food Quality, Safety and Innovation, 4600 Wels, Austria
3
Johannes Kepler University, Institute for Chemical Technology of Organic Materials, 4040 Linz, Austria
4
PM International AG, 5445 Schengen, Luxembourg
5
NBNC—North Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
6
Obesity Research Unit, Paracelsus Medical University, 5020 Salzburg, Austria
7
Department of Pediatrics, Paracelsus Medical University, 5020 Salzburg, Austria
*
Author to whom correspondence should be addressed.
Nutrients 2019, 11(7), 1512; https://doi.org/10.3390/nu11071512
Received: 22 April 2019 / Revised: 24 June 2019 / Accepted: 27 June 2019 / Published: 3 July 2019
(This article belongs to the Special Issue Dietary Bioactives and Human Health)
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Abstract

Inhibition of intestinal glucose resorption can serve as an effective strategy for the prevention of an increase in blood glucose levels. We have recently shown that various extracts prepared from guava (Psidium guajava) inhibit sodium-dependent glucose cotransporter 1 (SGLT1)- and glucose transporter 2 (GLUT2)-mediated glucose transport in vitro (Caco-2 cells) and in vivo (C57BL/6N mice). However, the efficacy in humans remains to be confirmed. For this purpose, we conducted a parallelized, randomized clinical study with young healthy adults. Thirty-one volunteers performed an oral glucose tolerance test (OGTT) in which the control group received a glucose solution and the intervention group received a glucose solution containing a guava fruit extract prepared by supercritical CO2 extraction. The exact same extract was used for our previous in vitro and in vivo experiments. Blood samples were collected prior to and up to two hours after glucose consumption to quantitate blood glucose and insulin levels. Our results show that, in comparison to the control group, consumption of guava fruit extract resulted in a significantly reduced increase in postprandial glucose response over the basal fasting plasma glucose levels after 30 min (Δ control 2.60 ± 1.09 mmol/L versus Δ intervention 1.96 ± 0.96 mmol/L; p = 0.039) and 90 min (Δ control 0.44 ± 0.74 mmol/L versus Δ intervention −0.18 ± 0.88 mmol/L; p = 0.023). In addition, we observed a slightly reduced, but non-significant insulin secretion (Δ control 353.82 ± 183.31 pmol/L versus Δ intervention 288.43 ± 126.19 pmol/L, p = 0.302). Interestingly, storage time and repeated freeze-thawing operations appeared to negatively influence the efficacy of the applied extract. Several analytical methods (HPLC-MS, GC-MS, and NMR) were applied to identify putative bioactive compounds in the CO2 extract used. We could assign several substances at relevant concentrations including kojic acid (0.33 mg/mL) and 5-hydroxymethylfurfural (2.76 mg/mL). Taken together, this clinical trial and previous in vitro and in vivo experiments confirm the efficacy of our guava fruit extract in inhibiting intestinal glucose resorption, possibly in combination with reduced insulin secretion. Based on these findings, the development of food supplements or functional foods containing this extract appears promising for patients with diabetes and for the prevention of insulin resistance. Trial registration: 415-E/2319/15-2018 (Ethics Commissions of Salzburg). View Full-Text
Keywords: guava extract; oral glucose tolerance test; type 2 diabetes mellitus; supercritical CO2 extraction guava extract; oral glucose tolerance test; type 2 diabetes mellitus; supercritical CO2 extraction
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König, A.; Schwarzinger, B.; Stadlbauer, V.; Lanzerstorfer, P.; Iken, M.; Schwarzinger, C.; Kolb, P.; Schwarzinger, S.; Mörwald, K.; Brunner, S.; Höglinger, O.; Weghuber, D.; Weghuber, J. Guava (Psidium guajava) Fruit Extract Prepared by Supercritical CO2 Extraction Inhibits Intestinal Glucose Resorption in a Double-Blind, Randomized Clinical Study. Nutrients 2019, 11, 1512.

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