# US 10,767,054 B2 · Process for preparing indigo carmine

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,767,054 B2
- Document ID: US10767054B2
- Status: Granted
- Kind: B2
- Application number: 16/465,040
- Filed: 2017-11-27
- Published: 2019-09-26
- Granted: 2020-09-08
- Earliest claimed: 2016-12-01
- Assignees: Provepharm Life Solutions
- Applicants: Provepharm Life Solutions
- Inventors: Babak Sayah; Stéphane Queru; Michel Feraud; Nicolas Lopez
- Web page: https://patentgrep.com/patent/US10767054B2

## CPC

- C09B 7/02: Bis-indole indigos
- A23L 5/47: using synthetic organic dyes or pigments not covered by groups A23L5/43 - A23L5/46
- A61K 47/22: Heterocyclic compounds, e.g. ascorbic acid, tocopherol or pyrrolidones
- C09B 67/0096: {Purification; Precipitation; Filtration}
- A23V 2002/00: Food compositions, function of food ingredients or processes for food or foodstuffs
- C09B: ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES {, e.g. PIGMENTS}; MORDANTS; LAKES (fermentation or enzyme using processes to synthesise a desired chemical compound C12P)
- A23L: FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES, NOT OTHERWISE PROVIDED FOR; PREPARATION OR TREATMENT THEREOF (preservation thereof A23B)
- A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D)
- A23V: INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION

## Abstract

Process for preparing disodium 5,5′-indigosulfonate, the feedstock being indigo, this process including the following steps: i) the indigo is subjected to a sulfonation treatment resulting in a mixture that contains 5,5′-indigosulfonic acid, this process including: ii) a reduction treatment is applied to the mixture obtained in step i), and optionally a purification step, so as to obtain a composition including leuco-5,5′-indigosulfonic acid, iii) the leuco-5,5′-indigosulfonic acid is isolated from the composition resulting from step ii), iv) the leuco-5,5′-indigosulfonic acid resulting from step iii) is oxidized to give disodium 5,5′-indigosulfonate.

## Claims

### Claim 1

A process for preparing disodium 5,5′-indigosulfonate, the starting material being indigo, this process comprising the following steps:
i) indigo is subjected to a sulfonation treatment leading to a mixture which contains 5,5′-indigosulfonic acid,
ii) the mixture obtained in step i) is subjected to a reduction treatment, and optionally a purification step, so as to obtain a composition comprising leuco-5,5′-indigosulfonic acid,
iii) the leuco-5,5′-indigosulfonic acid is isolated from the composition derived from step ii) and,
iv) the leuco-5,5′-indigosulfonic acid obtained from step iii) is oxidized to disodium 5,5′-indigosulfonate.

### Claim 2 (depends on 1)

The process as claimed in claim 1, in which the reduction treatment of step ii) is performed using sodium dithionite in aqueous medium.

### Claim 3 (depends on 1)

The process as claimed in claim 1, in which the leuco-5,5′-indigosulfonic acid precipitates in the reaction medium on conclusion of step ii).

### Claim 4 (depends on 1)

The process as claimed in claim 1, in which step iii) includes the steps of:
iiia) filtration of the composition obtained from step ii) and,
iiib) recovery of the solid retained on the filter.

### Claim 5 (depends on 4)

The process as claimed in claim 4, in which step iii) also includes, after step iiib), at least one step iiic) consisting of washing the solid with an aqueous medium.

### Claim 6 (depends on 5)

The process as claimed in claim 5, in which step iiic) is applied from one to five times.

### Claim 7 (depends on 1)

The process as claimed in claim 1, in which the composition obtained on conclusion of step iii) includes at least 90 mol % of leuco-5,5′-indigosulfonic acid relative to the total number of moles of the composition.

### Claim 8 (depends on 1)

The process as claimed in claim 1, in which step iv) includes at least one step iva) consisting of a treatment with a base in alcoholic medium in the presence of an oxidizing agent.

### Claim 9 (depends on 8)

The process as claimed in claim 8, in which step iva) consists of a treatment with sodium ethoxide in ethanol, in the presence of an oxidizing agent.

### Claim 10 (depends on 8)

The process as claimed in claim 8, in which the oxidizing agent is gaseous oxygen.

### Claim 11 (depends on 8)

The process as claimed in claim 8, which also includes, after step iva), at least one step ivb) consisting of one or more washes with one or more alcoholic and/or aqueous-alcoholic solvents.

### Claim 12 (depends on 1)

The process as claimed in claim 1 wherein the process produces a composition comprising at least 99.5% of disodium 5,5′-indigosulfonate, the percentage being measured by high-pressure liquid chromatography with detection at 290 nm.

### Claim 13 (depends on 1)

The process as claimed in claim 1 wherein the process produces a composition in which no impurity is present in an amount of greater than 0.10%, the percentage being measured by high-pressure liquid chromatography with detection at 290 nm.

### Claim 14 (depends on 1)

A process of manufacturing a medicament or a diagnostic product comprising disodium 5,5′-indigosulfonate, this process comprising manufacturing of disodium 5,5′-indigosulfonate via the process as claimed in claim 1 and the introduction of the disodium 5,5′-indigosulfonate into a pharmaceutically acceptable support.

### Claim 15 (depends on 1)

A process of manufacturing a food composition comprising disodium 5,5′-indigosulfonate, this process comprising manufacturing of disodium 5,5′-indigosulfonate via the process as claimed in claim 1 and the introduction of the disodium 5,5′-indigosulfonate into a support that is compatible with a food application.