Woody-earthy opening with a particular watery-marine undercurrent that sets it apart from most sesquiterpenes. Drier and greener than bet a-caryophyllene, without the latter's peppery-clove bite. A subtle sage-like herbaceousness emerges in the mid-phase. On skin, the woody-mineral residue has the quiet persistence of damp stone after rain — clean, not heavy.
Evolution over time
Immediately
Immediately
Woody-green, earthy. Dry hop bitterness with a surprising watery-marine flash.
After a few hours
After a few hours
Sage-herbaceous heart. The watery facet integrates into a mineral-woody core. Earthy depth holds.
CAS 6753-98-6. A monocyclic sesquiterpene (C₁₅H₂₄, MW 204.35) also known by the obsolete synonym alpha-caryophyllene. Named after Humulus lupulus (common hops), the plant from which it was first isolated. It is a constitutional isomer of beta-caryophyllene: same atoms, different ring geometry. Where beta-caryophyllene is bicyclic with a strained cyclobutane ring, alpha-humulene is an 11-membered macrocycle with three internal double bonds. This open-ring architecture gives it a flatter, less spicy character.
The odour is woody and earthy at first contact, then reveals an unusual watery-marine quality — one of very few naturally occurring terpenes that does this. A dry, bitter-herbal quality sits underneath, recalling sage leaf rubbed between fingers. It lacks the peppery bite of bet a-caryophyllene. On blotter, it reads green-woody for the first hour, then settles into a quiet, almost mineral dryness.
Found abundantly in hops (up to 40% of total essential oil in noble varieties like Hallertau and Saaz), sage (Salvia officinalis), ginger (Zingiber officinale), and Cannabis sativa. The molecule co-occurs with beta-caryophyllene in virtually all of these sources. In brewing, the humulene-to-caryophyllene ratio above 3:1 defines the aromatic profile of European noble hops.
In perfumery, alpha-humulene is rarely used as an isolate. It enters compositions through hop absolute, clary sage oil, or ginger CO2 extracts. Its value lies in its watery-woody bridging capacity — connecting aquatic accords to herbal-green structures without synthetic ozonic notes. Vapour pressure at 25°C is approximately 0.01 mmHg, confirming moderate tenacity consistent with a heart-to-base position.
In brewing, the humulene-to-caryophyllene ratio in hop oil is a defining metric of hop nobility. Ratios above 3:1 characterise the classic European noble hops — Saaz, Hallertau Mittelfrüh, Tettnang, Spalt — and produce the floral-herbal-spicy aroma profile prized in pilsners and lagers. American-style hops tend toward lower ratios with higher myrcene, yielding citrusy-resinous character instead.
Extraction & Chemistry
Extraction method: Isolated from hop essential oil (Humulus lupulus) by steam distillation followed by fractional distillation to separate it from co-occurring beta-caryophyllene and myrcene. Supercritical CO2 extraction at 40-50°C and 150-400 bar is an alternative method that preserves thermolabile fractions. Hop oil yields are typically 0.5-1.5% of dried cone weight; within that oil, alpha-humulene comprises 15-40% depending on cultivar — noble varieties (Hallertau, Saaz) trend toward the upper range. Also available as a synthetic or semi-synthetic isolate. Plant yields of high-purity alpha-humulene remain inconsistent across species, and no single botanical source has been established as a reliable high-concentration supply.
Molecular Formula
C15H24
CAS Number
6753-98-6
Botanical Name
Major component of Humulus lupulus (hops), Zingiber zerumbet (shampoo ginger), Cannabis sativa
IFRA Status
No known restrictions
Synonyms
HUMULENE · ALPHA-HUMULENE · HUMULENE
Physical Properties
Appearance
Colourless to pale yellow liquid with a woody, earthy-spicy odour
Boiling Point
99.00 to 100.00 °C. @ 3.00 mm Hg
Flash Point
194.00 °F. TCC ( 90.00 °C. )
Specific Gravity
0.88900 to 0.89500 @ 25.00 °C.
Refractive Index
1.49900 to 1.50500 @ 20.00 °C.
In Perfumery
Background modifier and naturalistic bridge note. Alph a-humulene rarely appears as a standalone isolate in fragrance formulati on — it contributes through essential oils and absolutes that conta in it (hop absolute, clary sage, ginger CO2). Its principal value is the unusual watery-woody quality: it can anch or aquatic or marine accords in a natural, herbal context without resorting to synthetic ozonics like Calone. In herbal-aromatic families (fougère, aromatic chypre), it reinforces earthy depth. In cannab is-inspired or beer-inspired accords — a small but active niche — it provides the signature hoppy realism. Functionally, it works alongside bet a-caryophyllene, myrcene, and linalool in complex herbal bases. Its moderate tenacity (vapour pressure ~0.01 mmHg at 25°C) places it in the heart-to-base transiti on zone rather than as a true fixative.
