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

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).

Ginseng Extract Ameliorates the Negative Physiological Effects of Heat Stress by Supporting Heat Shock Response and Improving Intestinal Barrier Integrity: Evidence from Studies with Heat-Stressed Caco-2 Cells, C. elegans and Growing Broilers

“…Ginsenosides standards were obtained from Extrasynthese (Lyon, France). The extract was analysed with HPLC-MS after a modified protocol described elsewhere [26,58,59]. The samples were dissolved in methanol and separated on a Surveyor HPLC (Thermo Fisher Scientific, Waltham, MA, USA) equipped with an Accucore C18 column (150 mm × 3 mm, 2.6 µm; Thermo Fisher Scientific, Waltham, MA, USA) using a gradient of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B): from 80% A to 70% A in 5 min, to 55% A in 15 min, to 25% A in 10 min which was kept for 2 min.…”

Intestinal Fructose and Glucose Metabolism in Health and Disease

“…The effect of these extracts on glucose uptake in Caco-2 cells were related to inhibition of GLUT2, although the effects on fructose uptake were not assessed [111]. More recently, König et al demonstrated that fruit extracts prepared from guava inhibited intestinal glucose resorption in a clinical trial [112].…”

The Restorative Effect of Red Guava (Psidium guajava L.) Fruit Extract on Pulmonary Tissue of Rats (Rattus norvegicus) Exposed to Cigarette Smoke

“…Fruit. Extraction of guava fruit was conducted based on the modification of the earlier report [13]. 1.5 kilograms of red guava fruit were dried by aeration at room temperature, and then, 50 grams of the dried powder underwent Soxhlet extraction with 600 ml of nhexane for 6 hours.…”