γ-Elemene

Aroma and sensory profile

Gamma-elemene is a background sesquiterpene with a small voice. Fragrance references describe (−)-gamma-elemene, the natural form, neat as green, woody, and oily [2], and the gamma-elemene entry itself carries no organoleptic description at all [1]. In juniper berry and cassis bud oils it sits under the monoterpenes as a soft, slightly fatty green woodiness, contributing body rather than a note anyone would name. Its isomers beta- and delta-elemene, which move the double bonds around the same ring, are typed sweet and herbal respectively, and the family as a whole is credited with part of the floral character of magnolia and juniper.

The molecule is a monocyclic sesquiterpene with three double bonds, one of them an isopropylidene group on the ring, and two stereocenters, so it is chiral. Fragrance databases list the (−) form as the natural material [2]. No panel description of (+)-gamma-elemene was found, so no claim about how the two enantiomers differ in odor is made here.

Effects and research

No animal or human study of gamma-elemene was found. Its research is on parasites, insects, and cancer cells, all in vitro.

Against Leishmania amazonensis, pure gamma-elemene isolated from Eugenia piauhiensis oil had IC50 values of 9.8 micrograms per milliliter on promastigotes and 8.1 on amastigotes, with low toxicity to macrophages, acting through membrane damage and increased tumor necrosis factor alpha, interleukin-12, nitric oxide, and reactive oxygen species [3]. As an insecticide, gamma-elemene from Wedelia prostrata oil killed fourth-instar Spodoptera litura larvae with an LC50 of 10.6 micrograms per milliliter [4], and gamma-elemene from Eugenia uniflora leaf oil killed larvae of three mosquito species, Anopheles subpictus, Aedes albopictus, and Culex tritaeniorhynchus, at LC50 values of 10.5 to 12.2 micrograms per milliliter while sparing larvivorous fish and aquatic predators by safety factors of 56 to 273 [5]. In triple-negative breast cancer cell lines it was cytotoxic in a dose-dependent manner and impaired mitochondrial biogenesis through acetylation of PGC-1 alpha, an effect reversed by knocking out the acetyltransferase GCN5 [6].

None of this is a pharmacology of gamma-elemene in a person. The clinical literature that surrounds the name "elemene" concerns beta-elemene, the injectable, and does not transfer to the gamma isomer.

Natural sources

Gamma-elemene is a berry, bud, and myrtle-family terpene. Fragrance databases log it at 2.9 percent in juniper berry oil, up to 1.6 percent in cassis bud oil, 1.3 percent in angelica seed extract, 0.9 percent in betel leaf oil, 0.5 percent in Chinese star anise oil, 0.4 percent in hinoki leaf oil, and traces in cananga, cascarilla, cedrela, galangal, and jambu flower oils [1]. Its richest reported sources are in the myrtle family: it made up 13.6 percent of Eugenia uniflora leaf oil [5] and was the major constituent of Eugenia piauhiensis oil [3], and it reached 7.6 percent of Wedelia prostrata oil in the daisy family [4]. In cannabis gamma-elemene is a minor sesquiterpene, reported in a number of chemotypes at a small fraction of the caryophyllene level, usually alongside beta-elemene.

Boiling point and vaporization

No measured boiling point for gamma-elemene appears in PubChem or in a primary paper found for this profile, so none is listed. Fragrance references quote 257 to 259 °C at 760 mmHg but mark the value as an estimate [1], and the 229 °C the site previously listed had no traceable source. What can be said is that gamma-elemene is a fifteen-carbon hydrocarbon sesquiterpene in the same volatility band as caryophyllene and humulene, so it belongs among the base notes and persists in dried juniper berries and stored oils after the monoterpenes have gone. Its three double bonds make it oxidation-prone in air. No thermal degradation study of gamma-elemene was found.

Industries and uses

Fragrance: gamma-elemene contributes a soft green-woody, slightly oily body in juniper, cassis, and herbal accords and is used as a natural constituent of those oils rather than as an isolate [1][2]. No flavor, aromatherapy, or cosmetic use specific to gamma-elemene was found in the sources reviewed, and its only distinctive documented property, larvicidal activity that spares aquatic predators, belongs to pest control rather than to any industry tagged on this site [5].