A method is described for the detection of antimutagenic agents in a forward mutation assay with Salmonella typhimurium strain TM677. Bacterial cells are treated with test compounds in the presence of a known mutagen. Antimutagenic activity is indicated by a reduction in the induced mutant fraction. This assay has been used to detect and/or confirm the antimutagenic activity of a number of known compounds. This method is currently being used in our laboratory for the bioassay-directed fractionation of potential cancer chemoprevention agents from plant extracts.

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, (C) 1997 by John Wiley & Sons, Ltd.

Two novel, potently sweet 3,4-secodammaranoid saponins designated pterocaryosides A (1) and B (2) have been isolated from the leaves and stems of the Chinese tree Pterocarya paliurus. The structures of these compounds were established as (23E)-(12R,20S)-12,20,25-trihydroxy-3,4-secodammara-4(28),23-dien-3-oic acid 12-O-beta-D-quinovopyranoside and (23E)-(12R,20S)-12,20,25-trihydroxy-3,4-secodammara-4(28),23-dien-3-oic acid 12-O-alpha-L-arabinopyranoside, on the basis of spectroscopic measurements, especially 1D and 2D NMR data. The methylated peracetates of pterocaryosides A and B were prepared and used for structural confirmation. Preliminary evaluations constituted by mouse acute toxicity and bacterial mutagenesis determinations supported the safety of 1 and 2, and subsequently the compounds were rated by a human taste panel as about 50 and 100 times sweeter than 2% sucrose, respectively.

Selligueain A, a novel sweet trimeric proanthocyanidin with a doubly linked A unit, has been isolated from the rhizomes of Selliguea feei collected in Indonesia. The structure of this substance was established as epiafzelechin-(4 beta-->8, 2 beta-->O-->7)-epiafzelechin-(4 beta-->8)-afzelechin [1], on the basis of a combination of spectral and chemical methods. The compound was not acutely toxic for mice and not mutagenic in a forward mutation assay utilizing Salmonella typhimurium strain TM677. Selligueain A [1] was rated by a taste panel as exhibiting about 35 times the sweetness intensity of a 2% w/v aqueous sucrose solution, and at a concentration of 0.5% w/v in H2O was perceived as pleasant-tasting rather than astringent.