Variable effects of American ginseng:: a batch of American ginseng (Panax quinquefolius L.) with a depressed ginsenoside profile does not affect postprandial glycemia

Background: We have repeatedly reported that American ginseng (AG) with a specific ginsenoside profile significantly decreases postprandial glycemia. Whether this effect is reproducible using AG with a different profile is unknown. We therefore investigated the effect of a different batch of AG on glycemia following a 75 g oral glucose tolerance test (OGTT). Methods: Using a randomized, single blind design, 12 normal subjects (six males and six females, aged 31 +/- 3y, body mass index (BMI) 28 +/- 2 kg/m(2)) received 6 g AG or placebo 40 min before a 75 g OGTT. The protocol followed the guidelines for the OGTT, with venous blood samples drawn at - 40, 0, 15, 30, 45, 60, 90 and 120 min. Ginsenosides in the AG were assessed by established methods for HPLC-UV. Results: Repeated measures analysis of variance demonstrated that there was no significant effect of the AG on incremental plasma glucose (PG) or insulin (PI) or their areas under the curve Indices of insulin sensitivity (insulin sensitivity index (ISI)) and release (DeltaPI(30-0)/DeltaPG(30-0)) calculated from the OGTT were also unaffected. The AG contained 1.66% total ginsenosides, 0.90% (20S)-protopanaxadiol (PPD) ginsenosides, and 0.75% (20S)-protopanaxatriol (PPT) ginsenosides, with the following key ratios: PPD:PPT of 1.2, Rb-1:Rg(1), of 8.1, and Rb-2:Rc of 0.18. Conclusions: The present batch of AG was unable to reproduce the postprandial hypoglycemic effects we observed previously. Possible explanations for this discrepancy include marked decrements in total ginsenosides and the key ratios PPD:PPT, Rb-1:Rg(1), and Rb-2:Rc. These data suggest that the ginsenoside profile of AG might play a role in its hypoglycemic effects. The involvement of other components cannot, however, be precluded.