Abstract
Although numerous experiments have demonstrated the sweetness-inhibiting effects of Gymnema sylvestre extracts, no human psychophysical studies have been done to quantitatively assess G.sylvestre's effects across a set of natural and intensive sweeteners. The present study evaluated the sweetness-inhibiting effects of G.sylvestre extracts on three concentrations each of acesulfame K, aspartame, sodium cyclamate, fructose, glucose, sucrose, stevioside and xylitol. Subjects made sweetness judgements of the stimuli following pretreatment with either distilled water, commercial tea or G.sylvestre extracts. Gymnema sylvestre pretreatment reduced the sweetness of the stimuli by an average of 77% with no evidence for a differential effect across sweeteners. The percentage reduction in sweetness was constant across the low, medium and high concentrations of the sweeteners. Kinetic plots of the data fit the Michelis-Menten model for non-competitive inhibition, but statistical results did not permit competitive or uncompetitive mechanisms to be ruled out. A receptor occupancy/blocking mechanism is unlikely. The results support disruption of a more general aspect of sweetness transduction and fit a type of 'mixed' inhibition involving an effect on the breakdown of the stimulus/receptor complex. Inhibition of a later step in a sequential-step transduction system and/or a change in the physicochemistry of the environment of the stimulus/receptor complex are possible.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 461-479 |
| Number of pages | 19 |
| Journal | Chemical Senses |
| Volume | 17 |
| Issue number | 5 |
| DOIs | |
| State | Published - Oct 1992 |
| Externally published | Yes |
Bibliographical note
Funding Information:We thank Hoechst, Maruzen and the Nutrasweet Co. for gifts of acesulfame K, stevioside and aspartame, respectively. We also acknowledge D.Nelson for discussion and comments on the manuscript, and J.Brink and T.Livdahl for discussion. L.Kennedy also thanks D.Lancet and the Weizmann Institute for Science for providing facilities and an excellent environment in which to complete the manuscript. This work was supported by an Ohio Board of Regents Research Challenge Grant to R.Frank and NIH Grant R15 NS24159 to L.Kennedy. A preliminary report of the experimental results was presented at the Tenth Annual Meeting of AChemS held at Sarasota, FL, April 1988, and published in abstract form (Mize and Frank, 1988). The kinetic analyses were presented at the Twelfth Annual AChemS Meeting in April 1990 (de los Santos et ai, 1990).