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

1. Identity & Chemical Information

Indole is a significant compound in the flavor and fragrance industry, known for its distinctive aroma. The IUPAC name for indole is 1H-indole. It is identified by the CAS number 120-72-9 and has a FEMA number of 2593. Other identifiers include the FL number 02.038 and CoE number 246. The molecular formula of indole is C8H7N, with a molecular weight of 117.15 g/mol. Indole contains a bicyclic structure consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. This structure is crucial for its odor characteristics, contributing to its floral and animalic scent profile.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

Indole is renowned for its complex sensory profile, characterized by a floral, jasmine-like aroma with animalic and fecal undertones. This duality makes it a powerful impact note in perfumery, where it is used to add depth and realism to floral compositions. The odor threshold of indole is relatively low, allowing it to be perceived at minute concentrations. In flavor applications, indole can impart a subtle, earthy note, enhancing the authenticity of certain fruit and floral flavors.

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 produced during 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 natural processes.

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

4. Use in Flavors

In the flavor industry, indole is used to enhance floral and fruity notes, particularly in berry and tropical fruit flavors. It serves as a background realism enhancer, providing depth and complexity. Typical use levels in food and beverages range from 0.1 to 5 ppm, depending on the desired intensity and the specific application. Indole is relatively stable under normal processing conditions but can degrade under extreme heat or acidic conditions.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

Indole is a staple in the fragrance industry, particularly in floral compositions such as jasmine, orange blossom, and tuberose. It acts as a modifier and impact note, adding a naturalistic and sensual quality to perfumes. Indole is typically used in trace amounts, often less than 1% of the total fragrance composition, due to its potent aroma. It contributes primarily to the middle notes of a fragrance, providing a bridge between the top and base notes.

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. The United Kingdom follows similar regulations post-Brexit. In Asia, indole is permitted in Japan and China under specific conditions, while ASEAN countries may have varying regulations. In Latin America, countries like Brazil and those in MERCOSUR generally align with international standards but may have specific national requirements.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

Indole's safety profile varies with exposure routes. For oral exposure, it is considered safe at low concentrations typical in flavor applications, with an acceptable daily intake (ADI) not clearly reported but generally recognized as safe at industry-typical levels. Dermal exposure in fragrances is monitored by IFRA, which provides guidelines to prevent irritation and sensitization. Inhalation exposure is generally low risk due to its low volatility, but occupational exposure should be managed to prevent irritation.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

Indole is valued for its ability to add authenticity and depth to both flavors and fragrances. It synergizes well with other floral and fruity notes, enhancing their naturalness. Formulators should be cautious of its potent aroma, as overuse can lead to an undesirable fecal note. It is often under-used in formulations where a subtle, naturalistic enhancement is needed.

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, although specific use levels may vary. Some data gaps exist in precise toxicological thresholds, but general safety is supported by extensive historical use.

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 2026-09-01 10:19:44 GMT (p2)