DE2840442C2 - Use of the diketopiperazine L-Leu-L-Trp as a flavoring for beverages with a bitter taste - Google Patents

Description

The invention relates to the use of diketopiperazine, which is the condensation product of L-leucine and L-tryptophan, as a flavoring for beverages with a bitter taste.

It is known to use bitter substances from plants for the production of beverages with a bitter taste to use. In addition to the hops contained in beer and extracts from artichokes, quinine is mainly used to create the bitter taste of beverages, for example bitter ones Sodas. Quinine has been used to treat malaria since ancient times; it causes however, even in relatively small doses, side effects such as dizziness, headache, heart problems. The replacement of quinine with physiologically harmless bitter substances would therefore be desirable.

In DE-OS 26 54 184 it is proposed that an ingredient of the artichoke, the "cynaropicrin", as to use bitter substance superior to quinine. Cynaropicrine is something compared to quinine more bitter, but shows a significantly higher acute toxicity.

It has now been found that the diketopiperazine

L-Leu-L-Trp

can be used particularly advantageously for the production of beverages with a bitter taste. Although the bitter threshold is slightly higher than that of quinine and cynaropicrine, the toxicity is less the diketopiperazines are considerably lower, so that there is a broader safety margin when they are used results. It is also advantageous that the diketopiperazines because of their great chemical stability in the body not metabolized, but excreted unchanged in the urine and thus not the organism burden unnecessarily.

The great chemical stability of diketopiperazine also has a beneficial effect in this respect. than it in the Drinks can be kept indefinitely at room temperature. In terms of durability, there is an opposite Cynaropicrin e: in clear advantage. While cynaropicrin after three hours of cooking in demineralized Water shows clear signs of decomposition, the diketopiperazines are not only available under these conditions, but also unchanged after three hours of boiling in 0.5 percent citric acid (pH 2.4). Accordingly, drinks with diketopiperazine as a bitter substance and concentrates do not stand out only characterized by their excellent shelf life; they can also be safely subjected to heat sterilization will.

Another advantage of diketopiperazine over the previously described ones obtained from plants Bitter substances consists in the fact that they are easily fully synthetic in the highest purity and consistent quality can be produced.

The usual procedures are used for this.

For making a non-alcoholic bitter drink the diketopiperazine can be added as a solid or as a liquid concentrate. It will be called If solids are used, the slow rate of dissolution often falls (depending on the structure and grain size) on. This property can be suppressed by a grinding process; as particularly advantageous but the following procedure has surprisingly been found: The diketopiperazine is in dissolved in a suitable organic solvent and applied to a solid support. According to the invention z. B. the crystal sugar intended for lemonade production in a coating pan with the saturated alcoholic diketopiperazine solution, which may also contain a crystallization retarder, sprayed and the solvent evaporates at the same time. You-granulated sugar is now covered with a thin layer of the Diketopiperazine coated. When this sugar is dissolved in water, the diketopiperazine dissolves the fine distribution just as quickly as the sugar itself. Instead of granulated sugar can also Use sugar substitutes such as sorbitol, mannitol or fructose or sweeteners such as. B. Cyclamate. Other additional bitter substances can also be absorbed on the carrier.

For the production of a lemonade with a bitter taste, the carrier coated with bitter substance can be used as such a syrup or a syrup made therefrom can be used. The manufactured according to the invention Drinks can e.g. B. also contain: Physiologically compatible acids, essences, aromatic substances, bitter substances, Sweeteners, colorings, table salt.

In addition to the production of non-alcoholic beverages, the diketopiperazine can also be used for the production of alcoholic beverages such as bitter vintages, bitter liqueurs, Vermuth types, aperitif drinks and Beer can be used. In these cases, ethanolic solutions of diketopiperazine can also be advantageous are used for production.

Production of the diketopiperazine L-Leu-L-Trp

(The amino acids and their derivatives mentioned below are each in the L-form.) 456 g of Boc-Trp-OH (1.5 mol) and 151 g of N-Methylmor-

pholine (1.5 mol) are dissolved in 4 l of dimethylformamide (DMF), cooled to - 15 ° C and treated with 191 g of chloramine

isobutyl acid ester (1.4 mol) was added. After 15 minutes, the solution, cooled to -5 ° C., of 235 g of H-LeU-OCH ₃ · HCl (1.3 mol) and 131 g of N-methylmorpholine in 1 1 of DMF is added. The mixture is stirred for one hour at 0 ° C. and overnight at room temperature. from

b5 precipitated salt is filtered off, the filtrate in Freed from DMF in a high vacuum, an oil would be obtained will. When the oil is absorbed in ethyl acetate, salt is again deposited, which is then separated off. The received

Solution is at 0 ⁰ C 3 times with 1 N sodium hydroxide solution, water and 3 times alternately with sat. KSO ₄ solution and water are extracted by shaking. The organic phase is _{dried over MgSO 4} and concentrated, 377 g of Boc-Trp-Leu-OCH ₃ (= 67% of theory) being obtained as an oil.

377 g of Boc-Trp-Leu-OCH ₃ (0.88 mol) are poured with 3 l 1 N-HCl in glacial acetic acid and stirred for one hour at room temperature. The HCl-glacial acetic acid mixture is distilled off under reduced pressure and the residue is mixed 3 times Evaporated ether and acetone. After taking up the residue in Essigester is washed at 0 ⁰ C, 3 times each with NaHCO ₃ solution and water, dried over MgSO ₄ and concentrated Thus, 255 g of H-Trp-Leu-OCHj (= 88% of theory) as an oil obtain.

255 g of H-Trp-Leu-OCH ₃ (0.77 mol) are mixed with 2.5 1 of toluene and 320 ml of sulfolane, refluxed for 14 hours and cooled Acetone washed and dried. It is recrystallized from ethanol

Yield 164 g of Trp-Leu = Leu-Trp (a 71% of theory)

Mp 265-266 ° C.

Elemental analysis:
calculated C 68.20
found C, 68.60

H 7.07 H 7.14

N 14.04% N 13.65%

Examples of coating granulated sugar with the diketopiperazine Leu-Trp

Example 1 Coating without a crystallization retarder

1000 g of granulated sugar with a grain size distribution of 0.5-2 mm are placed in a coating pan at 40 ° Inclination and a rotation speed of 40 rpm with weak dry air of 35 ° C with a solution from

7 g Leu-Trp

sprayed in 200 ml of methanol over 30 minutes. The sugar loaded with diketopiperazine differs in its flow properties not from the initial sugar.

Example 2

Coating with the addition of a crystallization retarder

The procedure is as in Example 1, with the difference that the methanolic diketopiperazine solution 30 g of commercially available polyvinylpyrrolidone are added. The sugar obtained in this way is also in his Flowability not impaired.

Example of the production of a bitter lemonade

Basic material:

1.0 kg commercial lemon essence (1%)
1.0 kg aqueous citric acid solution (50%)
1.0 kg aqueous tartaric acid solution (50%)
0.3 kg aqueous lactic acid solution (50%)
1.7 kg of water

ίο 5 kg of this raw material become 60% with 95 kg Sugar solution that

0.45% Leu Trp

contains (obtained by dissolving the coated sugar from Example 7), mixed. Will be in the bottle this mixture was diluted with ten times the amount of water which was saturated with carbonic acid at 4 atmospheres. The resulting lemonade has a pH of 2.7-2.9.

Example 3
Comparison with quinine as a bitter substance

In a triangle and pair test, quinine hydrochloride dihydrate was found to 103 mg / 1 against the diketopiperazine

L-Leu-L-Trp

to 300 mg / 1 in a lemonade base solution of the composition (per liter):

0.5 g citric acid

0.5 g of tartaric acid

0.15 g of lactic acid

57.0 g granulated sugar

checked.

The evaluation according to DIN 10 951 (triangle test) and DIN 10 954 (pairwise difference test) resulted with a probability of 95% no significant preference for one of the two bitter substances.

In an additional, oriented test with 200 ppm (instead of the 300 ppm used in the above test), no difference whatsoever to quinine was observed.
A main advantage of the diketopiperazine to be used according to the invention is its low toxicity. In the mouse, the LD ₅₀ for the diketopiperazine is> 4 g / kg, while it is 0.5 g / kg for quinine, so that the ratio is greater than 8: 1. Although the diketopiperazine has to be dosed about twice as high as quinine, it still offers considerably greater safety in use. Quinine also shows considerable side effects. For example, a dose of 0.033 g / kg can cause deafness, blindness and heart problems in humans. Animal experiments with diketopiperazine - at doses of up to 4 g / kg - do not give any indications of similar side effects with this substance.

Claims (2)

Patent claims: 1. Use of diketopiperazine, which is the condensation product of L-leucine and L-tryptophan represents, as a flavoring for drinks with a bitter taste. 2. Use of the diketopiperazine according to claim 1, applied as an ethanolic solution a water-soluble solid carrier such as crystal sugar, sugar substitutes or sweetener and optionally with a content of other bitter substances, colorants and / or additives in the ethanol solution.