United States Patent [191 [11] Patent Number: 4,808,409 Kinghorn et a1. [45] Date of Patent: Feb. 28, 1989 [[54] LOW CARIOGENIC SWEETENING AGENTS OTHER PUBLICATIONS [75] Inventors: Alan D. Kinghorn; Cesar M. Compadre et al., Science, vol. 227, pp. 417-419, a Compadre, both of Chicago; John M. (1/25/ 85). Pezzuto, Glen Ellyn, all of I11. Bohlrnann et al., Phytochemistry, vol. 17, pp. 475-482 (1978). [73] Assignee: Board of' Trustees, University of Takeda et al., Chemical Abstracts, vol. 76, No. 59779h, , Illinois, Urbana, Ill. (1972). Bohlmann et 211., Chemical Abstracts, vol 90, N0. [21] Appl. No.: 641,526 l04133v, (1979). [22] Filed: Aug. 16, 1984 Harwood et al., Chemical Abstracts, vol. 94, No. 103585q, (1981). [51] Int. Cl.4 .............. ..... .. A61K 7/16; CO7C 49/713 Primary Examiner--Bruce D. Gray [52] US. Cl. .................................... 424/439; 424/49; Assistant Examiner-—Grace Hanks 1 426/548; 574/690; 568/377 Attorney, Agent, or Firm-Philip Hill [58] Field of Search ...................... .. 568/377; 426/538; 424/548, 49, 58, 439; 514/690 [57] ABSTRACT Racemic hernandulcin, a sesquiterpene, possesses a [56] References Cited , sweetness intensity about three orders of magnitude U.S. PATENT DOCUMENTS greater than that of sucrose. It is non-mutagenic and 3,839,421 10/ 1974 Schwieber ........................ .. 568/377 non-toxic under conventional assay procedures. In ad 4,136,119 l/1979 Hunter et a1. .. 568/377 dition to attractive utility in foods, beverages and phar 4,245,109 l/1981 Mayer et a1. 568/377 maceutical compositions, it affords a low-cariogenic, 4,246,292 1/ 1981 Konst et al. ....................... .. 568/377 essentially non-nutritive sweetening agent for inclusion in oral hygiene products. FOREIGN PATENT DOCUMENTS 1 58-183639 10/1983 Japan .......... ..................... .. 568/377 10 Claims, 1 Drawing Sheet‘ STRUCTURE OF HERNANDULCIN 0 OH 4,808,409 1 2 beverage additive, and as a flavor component of various LOW CARIOGENIC SWEETENING AGENTS pharmaceutical compositions, including oral hygiene products. The sweetening agents of this invention are This invention was made with Government support characterized as possessing two adjacent asymmetric under contract NOl-DE-02425, awarded by the Na centers involving both a cycloaliphatic ring structure tional Institute of Dental Research, National Institutes and an alkyl substituent. A typical sweetening agent of of Health. The Government has certain rights in this this invention is hernandulcin, whose structure is set invention. forth in FIG. 1. The optically active dextro stereoiso BACKGROUND OF THE INVENTION mer of hemandulcin has been found to occurin the Mexican herb, Lippia dulcis Trev., known as asweet It is generally agreed that there continues to be a need plant by the Aztec people. The inventors have eluci for highly effective non-nutritive and non-cariogenic dated the structure of hernandulcin, devised a method sweetening agents. Insufficient information exists for a for synthesis of hemandulcin and analogs thereof, and rational design of novel, sweet-tasting molecules which determined their utility for inclusion in foodstuffs and can serve as prototypes for the development of sweeter 5 related products for human or animal use. and safer compounds. Hernandulcin, or 6-(l’,5’-dimethyl-l’-hydroxyhex-4' Incidental to a study of perfumes and odor-modifying en-l'-yl)-3-methyl-2-cyclohexen-l-one, in its optically agents, Kovats, et al., in U.S. Pat. No. 3,928,456, discov active form, is extremely sweet, being some 1,000 times ered that certain cycloaliphatic, unsaturated ketones as sweet assucrose when compared on a molar basis (at possessed ?avoring and taste-modifying properties. 20 0.27 molar sucrose) and about 1,500 times as sweet Similar discoveries were reported by Schulte-Elte, et when compared on a weight basis. The synthetic, race al., in U.S. Pat. No. 4,147,672. mic mixture of levo and dextro stereoisomers of hernan Resort to the plant kingdom has afforded several dulcin likewise possesses a very attractive sweetness types of intensely sweet compounds, including a dihy intensity, about one-half that of the isolated natural ‘droisocoumarin (phyllodulcin), certain glycosides, and 25 product. the proteinaceous thaumatin, all of which serve as sugar The sweetness of hemandulcin is believed to be asso substitutes in one or more countries. ciated with asymmetry of the 6 and 1' carbon atoms as An optically active, sweet sesquiterpene, hernandul well as with the proximity of the keto and hydroxyl cin, has been isolated from the herb Lippia dulcis Trev. groups. Various analogs of hemandulcin are set forth in (V erbenaceae) which is indigenous to Mexico. Follow 30 FIG. 2, where taste properties related to the oxygen ing elucidation of its structure, methods have been de containing groups remain essentially unaffected by sub vised for the synthesis of related structures. stitution of hydrogen or a lower alkyl group at the R2 SUMMARY OF THE INVENTION position. Variation in substituents R1 and R3 can be effected to include alkyl or alkene groups and particu This invention relates to novel, low-cariogenic sweet 35 larly hydroxyl or carboxyl groups for increasing the ening agents, including racemic (i)-hernandulcin, their water solubility of the sweetening agent. Hernandulcin method of manufacture and their use in a variety of is soluble in water to the extent of about 0.5 gram per beverages, foodstuffs, and pharmaceutical composi liter. While this is generally suf?cient, because of the tions, including oral hygiene compositions. These intense sweetness exhibited, modification of structure to agents are many times greater than sucrose while being 40 improve water solubility in various foodstuff formula essentially non-nutritive. tions is available as may be desired. For example, hy Racemic hemandulcin has been found to be non droxyl-containing substituents at R1 or R3 positions may ‘ mutagenic and non-toxic and thus especially suited for be further modified by conversion to disodium phos use in a broad variety of food products, including can phate esters or monosodium succinate esters. Similarly, dies and other confectioner’s products. The sweetening 45 carboxyl-containing substituents at R1 or R3 positions agent compositions of this invention are based on a may be further modified by conversion to alkyl esters, sesquiterpene- structure, having adjacent asymmetric such as methyl esters, to alkali metal salts, such as a centers involving one carbon atom of the cycloaliphatic sodium or potassium salt, or to glycosyl esters, such as . ring and its adjacent substituent carbon atom, serving as a glucose or rhamnose ester. the anchoring member of the aliphatic sidechain. Hernandulcin is non-mutagenic when tested with The novel beverage, food, and pharmaceutical com Salmonella typhimurium strain TM677 and is non-toxic positions of this invention employ small but taste-effec for mice as assessed by acute toxicity studies employing tive concentrations of the sweetening agents. oral administration. Hernandulcin is relatively stable to The process of manufacture for these novel sweeten hydrolysis over a wide pH range in tests conducted at ing agents affords an optimized, yet simple, procedure 55 temperatures up to about 60° C. Its principal decompo for isolation of the desired products. sition products are 3-methyl-2-cyclohexen-l-one and DESCRIPTION OF THE DRAWINGS 6-methyl-5-hepten-2-one. These products, particularly the latter, were essentially non-toxic for mice when FIG. 1 presents the structure of hernandulcin, as tested as above. I established by spectroscopic and degradation proce These characteristics of the synthetic, racemic - dures. ' . ' (i)-hernandulcin make possible its use in a variety of ' FIG. 2 presents selected analogs of hernandulcin, beverages as a sweetening agent. Where a greater water including analogs having enhanced solubility in water. solubility is desired a selected analog, as discussed DESCRIPTION OF THE INVENTION above, may be employed. Any particular beverage for mulation, containing a taste-effective concentration of This invention relates to certain novel and low cario the sweetening agent of this invention, may also contain genic sweetening agents, useful as a non-nutritivedi other additive agents as desired for taste modi?cation or etary substitute or supplement for sucrose, as a food or ‘ intensity. In general, the sweetening agents of this in 4,808,409 3 4 vention should be employed at concentrations in the disilylamide, and lithium 2,2,6,6-tetra-methylpiperidide. range from about 0.05 to about 0.50 grams per liter of A typical boron triflate is di-n-butylboron trifluoro aqueous solution. In liquid concentrates an analog hav methyl sulfonate. Preferably the reaction solution also ing greater solubility is preferred. In solid powders, a contains a small amount of 2,2’-dipyridyl. The reaction preferred analog is an alkali metal salt derivative inas is conducted, with mixing, at a temperature within the much as hernandulcin and many of the speci?ed analogs range from about —78° to —O° C., preferably about are oils. An alternative formulation employs the sweet —20° C. to about —10° C., and most preferably about ening agent adsorbed on other solid components of the —-l5° C., and under an inert atmosphere, usually af powdered concentrate for beverage use. In any in forded by gaseous nitrogen. Agitation is continued for tended beverage formulation, any one or more of the from about 5 to about 15 minutes and the reaction mix sweetening agents of this invention may be employed. ture is quenched with the addition of a saline solution, When employed as a sweetening agentor ?avor mod such as 10% aqueous ammonium chloride. The reaction i?er in various foodstuffs, including candies and other product is extracted from the aqueous mixture with, for confectioner’s products, any one or combination of the example, diethyl ether, recovered by distillation of the agents of this invention, preferably racemic hernandul 15 ether solvent, and the recovered product oil is distrib cin, may be incorporated as an additive in the desired uted on high-surface area silica gel.