Dereplication of Saccharide and Polyol Constituents of Candidate Sweet-tasting Plants: Isolation of the Sesquiterpene Glycoside Mukurozioside IIb as a Sweet Principle of Sapindus rarak

In the search for new potently sweet compounds from plants, the rapid identification and quantification of free sugars and polyols in a crude plant extract is important for dereplication purposes, wherein compounds of known structure or biological activity are removed from further consideration. Accordingly, plants found to have high levels of free sugars and polyols are regarded as lower priority leads when screening for novel natural sweeteners. In the present study, gas chromatography–mass spectrometry was used to examine the sugar/polyol content of six sweet‐tasting species, comprised of the pericarp of Dialium indum L. (Leguminosae), the stem of Drypetes floribunda Hutchinson (Euphorbiaceae), the fruit of Hymenaea oblongifolia Huber var. palustris (Ducke) Lee and Langenheim (Leguminosae), the rhizomes of Imperata cylindrica (L.) Beauvois (Gramineae), the fruit of Manilkara zapota (L.) van Royen (Sapotaceae), and the pericarp of Sapindus rarak DC. (Sapindaceae). The total yields of sugars/polyols in these plant parts were 1.9, 6.1, 7.8, 4.5, 10.8 and 2.9% w/w, respectively. Several uncommon polyols were identified, including bornesitol in D. floribunda and quebrachitol in S. rarak. It is likely that the sweet taste of the plants containing more than 5% of sugars/polyols is imparted as a result of the high free sugar and/or polyol content. Owing to its low level of free sugars, S. rarak pericarp was chosen for further study, and the known sesquiterpene glycoside mukurozioside IIb (1) was isolated in high yield (6.3% w/w) as a sweet‐tasting constituent. Preliminary evaluations, comprised of mouse acute toxicity and bacterial mutagenesis determinations, indicated the safety of 1. The compound was subsequently rated by a human taste panel as having about the same sweetness potency as sucrose. © 1997 by John Wiley & Sons, Ltd.