C005 — Iscotrizinol (Diethylhexyl Butamido Triazone / Uvasorb HEB)
Section 1: Identity
| Property | Value | Confidence |
|---|---|---|
| INCI | Diethylhexyl Butamido Triazone | C1 |
| USAN | Iscotrizinol | C1 |
| IUPAC | Bis(2-ethylhexyl) 4,4'-[(6-{[4-(tert-butylcarbamoyl)phenyl]amino}-1,3,5-triazine-2,4-diyl)bis(azanediyl)]dibenzoate | C1 |
| Trade name | Uvasorb HEB (3V Sigma) | C1 |
| CAS | 154702-15-5 | C1 |
| Molecular formula | C₄₄H₅₉N₇O₅ | C1 |
| Molecular weight | 765.98 g/mol | C1 |
| Appearance | White-to-cream powder; oil-soluble | C2 |
Note: Iscotrizinol is a UVB filter with some UVA-II overlap — it is included in this UVA-organic claim set per the requested research scope, but technically its strongest absorption is UVB (peak 310 nm). It does not contribute meaningfully to UVA-I (340–400 nm) protection.
Regulatory status
| Region | Status | Max concentration |
|---|---|---|
| USA (FDA) | Not approved as OTC sunscreen active. TEA submitted; FDA 2014/2017 determination requested more safety data; GRASE pending | (TEA pending) |
| EU (Annex VI, entry 26) | Approved | 10% |
| Australia (TGA) | Approved | 10% |
| Japan | Approved | 10% |
| South Korea, ASEAN, Mercosur, Brazil | Approved | 10% |
Wikipedia notes "approved by US FDA, SCCS, TGA" but this is misleading: FDA has not approved iscotrizinol as a GRASE OTC sunscreen active. The TEA remains pending. Distinguishing between EU/AU approval and US OTC approval is important. C2.
Typical use concentration
- 1–10% in EU/AU/JP/KR products; 2–6% common
- Often combined with avobenzone, DHHB, MBBT for broad-spectrum coverage
- Selected when high SPF and excellent photostability are required at moderate cost
Section 2: UV Absorption Spectrum
Iscotrizinol is a strong UVB absorber with high specific extinction. The chromophore is a triazine-bridged tris-aryl system (similar topology to ethylhexyl triazone and bemotrizinol).
| Quantity | Value | Confidence |
|---|---|---|
| λmax | 310 nm (UVB) | C1 |
| Absorption range | ~280–340 nm (UVB + edge of UVA-II) | C1 |
| ε at λmax | ~110,000 M⁻¹cm⁻¹ (very high; "highest specific extinction among approved UVB filters per molecule" — 3V Sigma technical claim) | C2 |
| E(1%, 1cm) at 310 nm | computed: 110,000·10/766 ≈ 1435 (per 3V Sigma claim of "high specific extinction") | C3 |
| Bandwidth | FWHM ~30 nm (narrow, UVB only) | C2 |
The high ε per molecule combined with very high MW (~766 g/mol) means the ε per gram is moderate (per gram extinction is what dictates SPF efficiency in formulation real estate). However, in absolute SPF contribution, iscotrizinol delivers strong UVB protection at low concentrations.
There is negligible absorption above 360 nm — iscotrizinol does not protect UVA-I.
Section 3: Photodegradation Kinetics
Iscotrizinol is exceptionally photostable. Often cited as one of the most photostable UV filters in commercial use.
Photoprotection mechanism
Triazine-anilinobenzoate scaffold with multiple amide N-H bonds creates a network of intramolecular H-bonds and rapid non-radiative deactivation pathways. Likely mechanisms include: - Ultrafast IC via amide N-H torsional / inversion modes - Excited-state proton-transfer between amide N-H and triazine N - High vibrational coupling in the rigid fused chromophore lattice
Empirically: behavior consistent with high Φ_IC, very low Φ_T, very low Φ_chemistry.
Quantitative data
| Parameter | Value | Conditions | Source / Confidence |
|---|---|---|---|
| % SPF retained after 25 hours sunlight equivalent | ~90% (only ~10% loss) | Cited by manufacturer / multiple secondary sources | C2 (manufacturer claim, repeated in independent reviews) |
| % remaining after 25 MED | >95% | typical sunscreen formulation | C2 |
| Triplet yield Φ_T | Very low (<0.05) | C3 | |
| Singlet oxygen Φ_Δ | Negligible | C3 | |
| Photoproducts | None identified at cosmetic-relevant doses | C2 |
The "loses only 10% over 25 hours" figure is repeated across product literature (3V Sigma Uvasorb HEB brochure, INCIDecoder, derm-approved.com, Typology, MDPI Cosmetics review). The original measurement appears to derive from manufacturer accelerated stability testing — independent peer-reviewed verification of this exact number is sparse, but qualitative photostability rankings consistently place iscotrizinol in the top tier alongside MBBT, bemotrizinol, and ethylhexyl triazone.
Effect of vehicle / formulation
- Highly stable in oils, esters, silicone vehicles
- Compatible with all common emulsifiers
- Does not require encapsulation
Photoproducts
No photoproducts of practical concern at cosmetic UV doses. Under extreme deep-UV irradiation, trace amide bond cleavage products would be expected but are not characterized in commonly cited literature.
Section 4: Photostabilization
Iscotrizinol stabilizes other filters
- Acts as a UVB "screening" filter, reducing UV reaching avobenzone, indirectly stabilizing the latter
- No evidence of triplet-triplet energy transfer to/from avobenzone
- Compatible across the formulator palette
Synergistic combinations
| Pair | Effect |
|---|---|
| Iscotrizinol + avobenzone | Compatible; enhances overall photostability via UV competition |
| Iscotrizinol + DHHB | Highly complementary (UVB peak 310 + UVA peak 354) |
| Iscotrizinol + MBBT (Tinosorb M) | Highly complementary; full broad-spectrum |
| Iscotrizinol + bemotrizinol (Tinosorb S) | Complementary peaks (310 vs 310/340); can both be present |
| Iscotrizinol + octocrylene | Compatible |
| Iscotrizinol + octinoxate | Compatible (no [2+2] issues — iscotrizinol has no cinnamate) |
Negative interactions
- None reported in the peer-reviewed literature
Confidence summary
- §1 Identity: C1
- §2 Spectrum: λmax 310 nm C1; ε C2 (manufacturer-derived, widely repeated); E(1%,1cm) computed C3
- §3 Photodegradation: 10%/25h figure C2 (manufacturer + secondary citations; primary Φ values C5 — exact quantum yields not in accessed literature)
- §4 Stabilization: C2
Key references
- 3V Sigma. Uvasorb HEB Technical Information — ulprospector / 3V Sigma product literature
- EU Regulation (EC) 1223/2009 Annex VI entry 26
- Wikipedia: "Iscotrizinol" (cross-check identity)
- PubChem CID 9810816 — chemical identity
- Cosmetics MDPI 10(4):101 (2023) — UV filter review
- SCCS opinions — health.ec.europa.eu
C5 / Unknown items flagged
- Primary peer-reviewed Φ_T and Φ_Δ for iscotrizinol — C5 (not located in available open literature; manufacturer claims used)
- Specific solvent-by-solvent λmax variation — C5 (only ethanol value commonly reported)
- Mechanism of photoprotection (ultrafast spectroscopy on iscotrizinol specifically) — C5 (analogous mechanisms inferred from related triazine filters)