DE3637826C1 - Process for extracting natural dyes from walnut shells and henna - Google Patents

Abstract

As an example of materials containing natural dyes, walnut shells and the powdered leaves of Lawsonia inermis (henna) were extracted with liquid or compressed carbonic acid while varying the temperature, pressure and moisture content, giving yields of active substance of up to 96 %. In comparison with conventional extraction methods, that proposed is more effective and less complex, as a result of which recourse to juglone as a cosmetic dye could be of interest.

Description

The invention relates to a method for extracting Henna and walnut shells with liquid or compacted Carbonic acid.

Both the henna known in antiquity as well Walnut shells contain natural dyes, which for cosmetic purposes (e.g. for coloring skin and Hair) can be used. The effective part of powdered leaves of the cypress shrub (henna) is that 2-hydroxy-1,4-naphthoquinone (Lawson). That is isomeric 5-Hydroxy-1,4-naphthoquinone (Juglon) is the most effective Part of the walnut shells.

In the course of an industrial application, the effective Substances as pure as possible and in a uniform composition, d. H. standardized, available. Therefore it is advantageous not the naturally grown dye carrier, but Use extracts.

According to the description in Römpp's chemistry dictionary (8th ed. 1983, keyword "hydroxy-1,4-naphthoquinones") is derived from the shredded shells of unripe walnuts using hydrojuglon Water dissolved out of the aqueous phase with ether extracted. The aromatic hydrojuglon (1,4,5-trihydroxynaphthalene) can then be oxidized to juglone.

According to another regulation (Beilstein VIII, 308) fresh or dried ("not fresh") walnut shells extracted directly with ether. After a few more Intermediate steps should then be obtained. in the technical scale was attempted using walnut shells Mixtures of e.g. B. pull out peanut oil and paraffin oil. However, there was none in the extracts obtained in this way Juglone more detectable, probably because juglone in it more stable hydrojuglon converted or decomposed (oxidized).

Surprisingly, it has now been found that Juglon with liquid or compressed carbonic acid in a simple manner and with good yields can be extracted. It should become interesting again, natural juglon as a dye insert, which means that used in the meantime synthesized "replacement" dyes are unnecessary would.

The usability of liquid or compressed gases (e.g. carbon dioxide) as solvent is from a Numerous literature references known. Although have gases no solvent properties under ambient conditions. Under increased pressure, in the liquefied or compressed Condition, however, gases can be used as solvents will. Below the critical temperature (31 ° C) can compress gaseous carbon dioxide by increasing the pressure and - when the steam pressure is reached - liquefied will.

With a further increase in pressure, the Liquid (to a small extent) can be compressed further. At the transition above the critical temperature from gaseous to compressed when pressure increases continuous, d. H. without a sudden increase in Density like the compression below the critical Temperature. Applications of extraction with carbon dioxide lie in the decaffeination of green coffee beans and in the production of hop ingredients. Other suggestions include a. the deoiling of seeds, the extraction of spices and herbs as well as decaffeination of roasted coffee and fermented tea.

Apparatus and methods for the extraction with compressed Gases are now widely known, so should the procedure can only be briefly described:

Flows through compressed and tempered carbon dioxide starting material presented in a pressure vessel and  loads with the extractable ingredients. In one second step is the mixture of solvents and dissolved. This requires solvability of the solvent can be drastically reduced, e.g. B. by Decrease in density, by dilution with a worse one Solvents (such as nitrogen or argon) or by Adsorption (e.g. on bentonite). The cleaned solvent is then withdrawn and returned to the circuit. The extract can be taken out of the separation tank via a valve be dissipated.

The process is continuous with regard to the solvent, with respect to the raw material in batches. Will be beneficial aiming for a completely continuous extraction, e.g. B. by using several extraction containers, or by introducing the extraction material into the high pressure container.

The following examples (1-7) are intended to illustrate the procedure found as well as their advantages. they seem in the same way for the extraction of henna.

Examples

The extraction conditions, the type of raw materials and the yields are shown in the table below.

In the fresh walnut shells of harvest 83 were medium High pressure liquid chromatography (HPLC) 0.36% juglone been found. The dried peels of harvest 82 contained only (still) traces of juglone (approx. 0.01%).

In each experiment, 80 grams of crushed walnut shells were used filled into the extraction container. Because the content of Water from the husks from harvest 82 and 83 different the yields refer to the Dry matter. Per hour, based on the dry matter, ten to fifteen times the amount of solvent pumped through the bed. After an extraction time  from about 3 hours the increase in extract was only insignificant, d. H. the extraction was exhaustive.

In the extracted walnut shells, HPLC no more juglones can be detected. The extracts were also tested for their juglone content by HPLC. Each after the extraction condition was the proportion of impurities (Hydrojuglon, breakdown products, other ingredients such as B. chlorophyll) different.

The highest yields were obtained under extraction conditions of 300 bar and 40 ° C achieved (table). On the other hand the juglone content is only 17%, so under certain circumstances Extraction conditions are preferable, which are low yield, but deliver a higher purity.

A humidification of the carbonic acid until saturation (Example 2) gives no improvement in yields. The yields in the extraction are from Example 5 previous year's walnut shells can be seen. Here was already greatly reduced by drying and storing the juglone content been. Therefore, because of the co-extracted Ingredients the proportion and thus also the yield Juglone low.  

table

Yield results from the extraction of walnut shells

Extraction conditions

Claims (2)

1. A process for the extractive extraction of natural dyes from walnut shells and henna, characterized in that carbon dioxide is used as the extractant at pressures up to 500 bar and at temperatures up to 100 ° C. 2. The method according to claim 1, characterized in that that at pressures from 100 to 300 bar and at Temperatures of 20 to 40 ° C is worked.