Ethereal Botanical | Ethereal Essence | Chip Quality | Oil Quality Marker | Oil Quality Chart
Oxygenated sesquiterpenes (high-quality indicators)
- Agarospirol, jinkoh-eremol, jinkohol / jinkohol II, oxo-agarospirol. Frequently cited as signature constituents of premium oils.
- 10-epi-γ-eudesmol, valerianol, allo-aromadendrene (oxygenated), selina-3,11-dien-9-ol / -one, sometimes selina-3,11-dien-14-oic acid. These repeatedly appear in high-grade profiles.
Characteristic but not sufficient alone
- α/β-agarofuran, α-/β-guaiene, 4-phenyl-2-butanone (jinkoh perfume note)—common in genuine oils, but total quality depends on the whole pattern.
Chromones (PECs) and related
- 2-(2-phenylethyl)chromones (PECs) are hallmark agarwood constituents; they track resin development/grade. Classic GC-MS can detect some, but LC-MS / GC-QTOF capture them more reliably. Use them to complement GC-MS of volatiles.
What “good” GC-MS looks like (rules of thumb)
- High oxygenation: Sum of oxygenated sesquiterpenes ≫ sesquiterpene hydrocarbons (typical of premium, aged resin).
- Marker presence & balance: Detect agarospirol + jinkoh-eremol (often together) with supportive eudesmols/selinenes; avoid dominance by light aromatics only.
- Consistent fingerprint: Multivariate models (e.g., OPLS-DA / Z-score) separate higher grades by these oxygenated notes and specific selina/eudesmol features.
- Chromone signal present (if using LC-MS/GC-QTOF): PECs track induction time and quality; relative PEC↓ and SES↑ over time can explain aroma differences—use both families to grade.
Adulteration red flags (via GC-MS)
- Phthalates or plasticizers (e.g., diethyl phthalate) and odd solvent peaks → likely cutting.
- Out-of-family terpenes at high % (e.g., strong linalool, citronellol, or synthetic musks) inconsistent with Aquilaria.
- Overly simple profile lacking agarospirol/jinkoh-eremol/eudesmols.
(General GC-MS adulteration principles; apply alongside reference chromatograms from authenticated oils.)
Minimal “marker panel” to report
| Class | Target compounds (examples) | Why it matters |
|---|---|---|
| Oxygenated sesquiterpenes | Agarospirol, jinkoh-eremol, 10-epi-γ-eudesmol, selina-3,11-dien-9-ol/-one, valerianol | Core high-grade odorants; correlate with premium oils. |
| Sesquiterpene frameworks | α/β-agarofuran, α/β-guaiene, allo-aromadendrene | Authentic Aquilaria backbone; helps verify species/region. |
| Aromatic ketones | 4-phenyl-2-butanone | Typical “jinkoh” note; supportive, not decisive. |
| Chromones (non-volatile)† | 2-(2-phenylethyl)chromones (PECs) | Track resin/grade; best via LC-MS or GC-QTOF. |
†Analyze PECs on LC-MS (or GC-QTOF) alongside GC-MS of volatiles for a complete picture.
Suggested QC workflow
- Acquire TIC on GC-MS (e.g., HP-5MS column) and identify markers by library + standards. Build a fingerprint library of authenticated oils.
- Quantify groups: report % area of (a) oxygenated sesquiterpenes, (b) sesquiterpene hydrocarbons, (c) aromatics/others.
- Score: (Oxygenated SES %) – (Hydrocarbon SES %) + presence/weight for agarospirol & jinkoh-eremol (binary +1 each).
- Cross-check adulterants and solvents; flag anomalies.
- (Optional) PEC panel by LC-MS/GC-QTOF to support grade/resin maturity.
Useful references (open-access where possible)
- Reviews/compendia of sesquiterpenes & chromones in agarwood oils (good marker lists).
- Studies distinguishing grades via chemometrics (OPLS, Z-score).
- PEC identification and resin/quality links (GC-MS/LC-MS).
- High-quality oil profiles showing agarospirol/eudesmol dominance.
- Recent profiling & safety window for A. malaccensis oils.
- Example compound tables differentiating samples by markers (e.g., selina-3,11-dien-9-ol, α-vetivone).