Salmonella spp. is an important target bacterium of long-term concern in microbial testing and is commonly found in food, feed, animal-derived samples, and related environmental samples. For culture medium R&D personnel, how to enable target bacteria and background microbiota to form phenotypes that are easier to observe and distinguish during culture has always been an important direction in Salmonella culture medium design.

In traditional Salmonella culture media, the H₂S reaction is a classic identification basis. Some Salmonella can produce hydrogen sulfide. After H₂S reacts with components such as iron salts in the medium, a black sulfide precipitate forms, so colonies can show a recognizable black characteristic. After long-term application, this judgment method of “H₂S production—formation of black precipitate” has become an important part of many traditional culture media.

However, with the development of Salmonella detection needs and culture medium technology, the approach of relying solely on the H₂S phenotype has gradually exposed limitations. Some Salmonella strains may be H₂S-negative or show atypical characteristics, and relying only on black precipitate cannot fully reflect the biochemical characteristics of target bacteria.

Thus, a new question arose:

Besides H₂S, can other stable biochemical characteristics of Salmonella itself be used to add a more intuitive identification signal to colonies?

The answer comes from microbial enzyme activity.

Rather than waiting for metabolites to form a black precipitate, it is better to find substrates that can recognize specific enzyme activities and convert enzyme activity information into an observable chromogenic signal. In this way, enzymatic characteristics that originally could not be directly observed can be converted into colors visible on the colony surface.

This is exactly the entry point for Magenta-Caprylate into Salmonella chromogenic medium systems.

Magenta-Caprylate is a C8 esterase chromogenic substrate. Its core design is not simply to add a color to the medium, but to use microbial enzyme activity to complete the conversion from “biochemical reaction” to “color signal”.

When microorganisms with corresponding C8 esterase activity act on Magenta-Caprylate, the enzyme catalyzes hydrolysis of the ester bond in the substrate, releasing an indolol intermediate. This intermediate then undergoes dimerization under oxidative conditions to form an insoluble magenta indigo-like product, which deposits near the colonies.

Therefore, the final magenta color seen is not simply the color presented by the substrate itself, but the result jointly produced by enzymatic hydrolysis and subsequent chromogenic reaction.

From the perspective of detection logic, this actually completes a very clear signal conversion:

C8 esterase activity is recognized → enzymatic hydrolysis of the substrate occurs → chromogenic intermediate forms and further oxidizes → colonies show a magenta signal.

For culture medium R&D, the value of this design lies in: turning the enzymatic characteristics of microorganisms into directly observable colony phenotypes.

If the H₂S reaction provides the identification signal of “black precipitate”, then Magenta-Caprylate provides a magenta signal based on C8 esterase activity.

The difference between these two approaches is not just the color, but the way microbial characteristics are utilized. Traditional H₂S media mainly use microbial metabolites for judgment; chromogenic media can further utilize the enzyme activities possessed by microorganisms. For Salmonella, when a chromogenic substrate capable of responding to related enzyme activity is added to the culture system, the biochemical characteristics of target bacteria can be expressed through colony color.

Magenta-Caprylate functions precisely under this logic.

In Salmonella chromogenic media, it can use related C8 esterase activity to produce magenta colonies, while the medium can also add different chromogenic substrates according to the enzymatic characteristics of other microorganisms, allowing different microbial groups to form different color performances.

One of the more representative designs is the dual chromogenic system composed of Magenta-Caprylate and X-Gal (CAS:7240-90-6). Magenta-Caprylate responds to C8 esterase-related activity and produces a magenta signal; X-Gal can be hydrolyzed by β-galactosidase-positive microorganisms to form blue colonies. In this way, the enzymatic characteristics of different microorganisms in the same culture system can be expressed through different colors, providing richer colony information for the preliminary identification of Salmonella.

This design also reflects the core idea of chromogenic media:

It is not just about finding a substance that “makes target bacteria change color”, but about using the correspondence between multiple enzyme activities and chromogenic substrates to allow different microorganisms to present different color phenotypes.

Therefore, the value of Magenta-Caprylate is not only “producing magenta”, but also that it provides a chromogenic identification dimension based on C8 esterase activity for Salmonella culture media.

From the traditional H₂S black precipitate to multi-color chromogenic detection based on enzyme activity, the identification method of Salmonella culture media has also gradually developed from a single biochemical reaction to a richer phenotype identification system.

⚠️Note: C8 esterase activity is stably expressed in the vast majority of Salmonella serovars, but literature has reported that some strains of individual serovars (such as Salmonella Dublin) have lower C8 esterase activity, and incubation time may need to be extended or other identification methods combined.

Chinese name: 5-Bromo-6-chloro-3-indolyl caprylate

English name: 5-Bromo-6-chloro-3-inoxyl caprylate

Abbreviation: Magenta-Caprylate

CAS No.: 209347-94-4

Molecular Formula: C16H19BrClNO2

Molecular Weight: 372.69

Specification: 1 g /5 g /25 g (custom packaging available)

Form: off-white crystalline powder

Catalog No.: G02020002

Color: Magenta

Inventory: In stock

1. Development of Salmonella Chromogenic Media

Used for the development of Salmonella chromogenic media and selective differential media, generating magenta colony signals through C8 esterase-related activity to assist preliminary differentiation of target bacteria from background microbiota.

Main applications:

• Development of Salmonella chromogenic media

• Selective medium formulation optimization

• Microbial detection reagent development

2. Food Safety Salmonella Detection

Used for the development and application of Salmonella detection media in food, feed, and related environmental samples, providing visual colony identification signals for target bacteria and improving the screening efficiency of suspicious colonies.

Main applications:

• Food Salmonella detection

• Feed microbial monitoring

• Third-party testing laboratory screening

3. Esterase Activity Research

Used for C8 esterase-related enzymology research and microbial enzyme activity analysis, converting esterase activity into observable color signals and providing a research tool for enzyme activity detection and substrate screening.

Main applications:

• C8 esterase activity research

• Microbial enzymology analysis

• Enzyme activity detection method development

✅ Mature application system, formulation development is well-supported

Magenta-Caprylate is a classic C8 esterase substrate for Salmonella chromogenic media, with long-term application accumulation in international standard methods and commercial products. Formulation development has mature references, with no need to validate substrate applicability from scratch.

✅ Precipitate-type signal, clear colony localization

The magenta precipitate generated after hydrolysis is insoluble in water and does not diffuse in the medium. Colonies have clear boundaries, facilitating counting and picking single colonies for subsequent confirmation. The magenta signal has maximum absorption at 565 nm, is intuitive to interpret, and is suitable for optical observation in routine laboratories.

✅ Supports multi-substrate chromogenic system design

Magenta-Caprylate can be combined with chromogenic substrates such as X-Gal, allowing different enzyme activities to correspond to different color signals, helping to build a Salmonella chromogenic culture system with multi-dimensional colony phenotypes. It enables multi-color differentiation of target bacteria and contaminants on the same plate, making interpretation more intuitive and formulation design more flexible.

✅ Domestic in-stock supply, more controllable lead time and cost

Compared with imported brands, GeneSeqTools Bioscience & Technology provides localized pricing and shorter lead times. Batch-to-batch stability has been verified by the quality control system, supporting stable supply from small-scale research to industrial scale. Specifications cover 1 g / 5 g / 25 g, with custom packaging available.