JP3198003B2 - Light fast fibroin-natural dye complex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a complex of fibroin and a natural pigment, which has a color inherent to the natural pigment, has a remarkably improved light fastness, and is a coloring agent for foods, cosmetics and pharmaceutical materials. It is optimally used as such.

[0002]

2. Description of the Related Art It has been reported that chlorophyll is stabilized by adsorbing it on bentonite which is a montmorillonite clay mineral (Biotech. Lett., 14 119-122, 19).
92). In this report, when chlorophyll a and b are dissolved in benzene and bentonite powder is added to the solution, chlorophyll molecules adsorb to the surface of the bentonite particles very easily. The maximum wavelength shifts to the longer wavelength side, and finally settles to a wavelength of 678 nm, which coincides with the absorption maximum wavelength of green leaves. However, this chlorophyll-bentonite composite is reported to be extremely stable to light.

Japanese Patent Application Laid-Open No. 61-37715 discloses that regenerated fibroin fine powder dyed with an acid dye is light-fast, but the acid dye used is a water-soluble synthetic dye. The product is used for makeup cosmetics and is not used for foods and pharmaceutical materials.

[0004]

The beauty of natural pigments is
The reason why natural dyes are not so often used, although they are superior in color and safety as compared with synthetic dyes, is that they are unstable to light, oxygen and the like, and discolor quickly. For example, chlorophyll contained in green leaves is stable and does not fade in green leaves, but that extracted with an organic solvent rapidly fades when exposed to light. In addition, carotenoids such as β-carotene, rutin, and astaxanitin discolor similarly to light. An object of the present invention is to develop means for preventing fading of a natural dye for effective use of the natural dye, and to further expand the field of application thereof.

[0005]

SUMMARY OF THE INVENTION The present invention is a complex in which a natural dye is bound to fibroin. Fibroin is
It is a protein of silk thread, which is composed of two kinds of proteins, fibroin and sericin. The central part of the silk thread is covered with fibroin and its surface is covered with sericin. When the silk thread is treated with alkali to remove sericin, a uniform fibroin protein can be obtained. Fibroin can be solubilized by a conventional method using calcium chloride, alcohol and water, and the fibroin precipitated by dialysis can be collected. Fibroin has been established as a method for solubilization and fine powdering, and is the most suitable material to be combined with a natural dye. The powder has a beautiful and white color, and has the ability to clearly express the color inherent to the natural pigment to be combined.

Examples of natural pigments include green chlorophyll, yellow carotenoid, red safflower pigment (cartamine), dark blue phycocyanin isolated from cyanobacteria, and red rice pigment. Of these natural pigments, chlorophyll and carotenoids are water-insoluble and are suitably used for the purpose of the present invention. To produce a complex of fibroin and a natural dye, the two solutions are mixed and, if necessary, stirred, and the complex is obtained as a precipitate. The precipitate is centrifuged and dried under reduced pressure or lyophilized to obtain a powder.

[0007]

Industrial Applicability The fibroin-natural dye complex of the present invention is characterized by being hardly faded by irradiation with visible light and ultraviolet light, and having remarkably light resistance as compared with a free natural dye. For example, free chlorophyll has an absorption maximum at 660 nm, while the complex has an absorption maximum at 744 nm and shifts to 84 nm longer wavelength by binding with fibroin. This fact seems to be related to photostability.
As described above, the fibroin-natural dye complex of the present invention has excellent light fastness and does not contain any substances that impair health, and thus is optimal as a coloring agent for foods, cosmetics, and medical materials.

[0008]

【Example】

Example 1 Fibroin-chlorophyll complex Fibroin powder was added to a mixed solution of water and ethanol,
Calcium chloride was added and dissolved therein. The solution became semi-opaque after several dialysis cycles. The chlorophyll dissolved in ethanol was added there. Since the solution immediately became porridge, it was left for 20 minutes after stirring and centrifuged to obtain a green precipitate. The precipitate was washed with water several times and freeze-dried to obtain a fibroin-chlorophyll complex powder. The spectrum of this powder was measured by an opal glass method, and showed an absorption maximum at 660 nm and 744 nm.

Example 2 Fibroin-β-carotene complex To a semi-opaque fibroin solution obtained in the same manner as in Example 1, β-carotene dissolved in acetone was added. Hereinafter, a powder of a fibroin-β-carotene complex having a bright yellow color was obtained in the same manner as in the case of the fibroin-chlorophyll complex. The spectrum of this powder measured by the opal glass method showed an absorption maximum at 440 to 450 nm.

Example 3 Fibroin-Safflower Pigment Complex A yellow pigment was extracted from dried safflower with water, and then a red pigment was extracted with an aqueous potassium carbonate solution. When citric acid was added to the extract, a vivid red color was formed, so fibroin powder was added thereto, and the mixture was stirred so as to be uniformly dispersed. A red precipitate was obtained by centrifugation. This was washed with water to remove the yellow pigment, and a bright red complex was obtained. Further, the powder of the fibroin-safflower pigment complex was obtained by freeze-drying.
The spectrum of this powder was measured by an opal glass method, and showed an absorption maximum at 524.5 nm.

Example 4 Fibroin-red rice pigment complex Red rice embryos were stirred in a 0.36% hydrochloric acid-methanol solution,
A bright red-purple pigment was extracted. An equal amount of water was added thereto, and the pressure was reduced to remove the alcohol. The mixture was stopped when the liquid volume was reduced to about half, the precipitate was removed, and fibroin powder was added to the supernatant, and the mixture was stirred overnight to be uniform.
This was centrifuged to obtain a purple-red precipitate. Vacuum drying (3
5 to 40 ° C.) to obtain a powder of a fibroin-red rice pigment complex. The spectrum of this powder was measured by an opal glass method and showed an absorption maximum at 528 nm.

Test Example The fibroin-chlorophyll complex and the fibroin-β-carotene complex prepared in Examples 1 and 2 were irradiated with visible light (60 W incandescent lamp) and ultraviolet light (254 nm), respectively, to examine light resistance. The absorbance of all of these powders was measured by the opal glass method as they were. Table 1 shows the results. In the table, the numbers are shown as relative values with the absorbance at each wavelength of irradiation time 0 as 100.

[0013]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-293907 (JP, A) JP-A-61-272272 (JP, A) JP-A-60-149512 (JP, A) 10507 (JP, A) JP-A-63-197464 (JP, A) JP-A-3-97761 (JP, A) JP-A-50-50425 (JP, A) JP-B-46-12309 (JP, B1) JP-B 32-5729 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09B 61/00

Claims (2)

(57) [Claims] 1. A complex in which a natural dye is bound to fibroin. 2. The complex according to claim 1, wherein the natural pigment is chlorophyll or a carotenoid.