FlavScents AInsights Entry for Indole (CAS: 120-72-9)

1. Identity & Chemical Information

Indole is a bicyclic aromatic compound with a distinctive structure that includes a benzene ring fused to a pyrrole ring. It is commonly referred to simply as "indole." The IUPAC name for indole is 1H-indole. Its CAS number is 120-72-9, and it is recognized by FEMA with the number 2593. Other identifiers include the FL number 02.015 and CoE number 246. The molecular formula of indole is C8H7N, and it has a molecular weight of 117.15 g/mol. The presence of the nitrogen atom in the pyrrole ring contributes to its unique odor profile, which is significant in both flavor and fragrance applications.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

Indole is known for its intense, animalic odor, often described as fecal or floral, depending on its concentration. At low concentrations, it imparts a floral, jasmine-like scent, making it valuable in perfumery for adding depth and complexity. The odor threshold of indole is relatively low, allowing it to be perceived at minute concentrations. In flavor applications, indole can contribute to the authenticity of certain fruit and floral notes, acting as an impact note or a background realism enhancer.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

Indole naturally occurs in a variety of plants and is a key component in the scent of jasmine and orange blossoms. It is also found in coal tar and is a byproduct of the bacterial decomposition of tryptophan in the intestines. Indole's presence in natural sources allows it to be designated as a "natural flavor" or "natural fragrance" under certain regulatory frameworks, provided it is derived from these sources.

Citation hooks: FlavScents; food chemistry literature; EFSA/JECFA monographs

4. Use in Flavors

Indole is used in flavor formulations to enhance floral and fruity notes, particularly in products like candies, beverages, and desserts. It is typically used at very low concentrations, often in the range of 0.1 to 1 ppm, to avoid overpowering the flavor profile. Indole is stable under typical food processing conditions but can degrade under extreme heat or acidic conditions, which formulators should consider during product development.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

In perfumery, indole is a crucial component in floral fragrances, particularly those mimicking jasmine, orange blossom, and gardenia. It serves as a trace realism enhancer and an impact note, providing depth and complexity. Indole is typically used in concentrations ranging from 0.01% to 0.1% in fragrance formulations. Its volatility allows it to contribute to both the middle and base notes of a fragrance composition.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

In the United States, indole is recognized as GRAS (Generally Recognized As Safe) by FEMA for flavor use. In the European Union, it is listed under Regulation (EC) No 1334/2008 with an assigned FL number, indicating its approved use in food flavorings. The United Kingdom follows similar regulations post-Brexit. In Asia, indole's use is subject to national regulations, with Japan and China having specific guidelines for its use in flavors and fragrances. In Latin America, countries like Brazil and those in MERCOSUR have their own regulatory frameworks, often aligning with international standards.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

For oral exposure, indole's safety is supported by its FEMA GRAS status, with typical use levels well below any established ADI (Acceptable Daily Intake). Dermal exposure in fragrance applications is generally considered safe, though IFRA provides guidelines to prevent irritation or sensitization. Inhalation exposure is minimal due to its low volatility, but occupational safety measures should be in place to minimize exposure during handling and formulation.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

Indole is valued for its ability to add authenticity and complexity to both flavors and fragrances. It synergizes well with other floral and fruity notes, enhancing their naturalness. However, formulators must be cautious of its potent odor, which can easily dominate a composition if overused. It is often under-utilized due to its challenging odor profile, but when used judiciously, it can significantly enhance a product's sensory appeal.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

The data on indole is well-established, with comprehensive sensory and regulatory information available. Industry practices are well-documented, though some variability exists in use levels due to its potent nature. Known data gaps are minimal, but ongoing research into its broader applications and safety profiles continues to refine its use guidelines.

Citation hooks: FlavScents

QA Check

• All required sections 1-9 are present
• "Citation hooks:" line is present under each section
• Flavor section includes ppm ranges
• Toxicology section covers oral, dermal, inhalation
• Regulatory section mentions US, EU, UK, Asia, Latin America
• If complex natural material: includes section 5a (not applicable here)

About FlavScents AInsights (Disclosure)
FlavScents AInsights integrates information from authoritative government, scientific, academic, and industry sources to provide applied, exposure-aware insight into flavor and fragrance materials. Data are drawn from regulatory bodies, expert safety panels, peer-reviewed literature, public chemical databases, and long-standing professional practice within the flavor and fragrance community. Where explicit published values exist, they are reported directly; where gaps remain, AInsights reflects widely accepted industry-typical practice derived from convergent sensory behavior, historical commercial use, regulatory non-objection, and expert consensus. All such information is clearly labeled to distinguish documented data from professional guidance or informed estimation, with the goal of offering transparent, practical, and scientifically responsible context for researchers, formulators, and regulatory specialists. This section is generated using advanced computational language modeling to synthesize and structure information from established scientific and regulatory knowledge bases, with the intent of supporting—not replacing—expert review and judgment.

Generated 2026-04-07 18:15:03 GMT (p2)