Phellandrene

Aroma and sensory profile

Phellandrene is dill's green backbone. Fragrance references type alpha-phellandrene terpenic with medium strength and describe it at 10 percent as citrus, herbal, terpene, green, woody, and peppery, with a flavor at 20 parts per million that is terpenic, citrus lime with a fresh green note [1]. Beta-phellandrene, its isomer with the second double bond moved outside the ring, is typed minty and terpenic and described as mint and turpentine [4]. Alpha is the softer, greener, dill-and-pepper one; beta is sharper and closer to the pinenes.

Alpha-phellandrene, p-mentha-1,5-diene, has one stereocenter and is chiral, and the enantiomers differ. (S)-(+)-alpha-phellandrene is described in a single word, dill, and is the form of dill, fennel, elemi, ginger grass, and turmeric [3]. (R)-(−)-alpha-phellandrene is described as terpene, spicy, and medicinal and is recorded at trace level in tea tree oil [2]. The (+) form is the herb-garden note; the (−) form the resinous, medicinal one. Beta-phellandrene is also chiral. This page treats alpha-phellandrene as the primary compound and beta as its companion.

Effects and research

No human trial of phellandrene was found. A 2022 systematic review of 99 papers on alpha-phellandrene catalogued antitumoral, antinociceptive, larvicidal, and insecticidal activities and concluded that toxicological data are still lacking [5]. The Research Institute for Fragrance Materials has assessed the (−)-alpha enantiomer and beta-phellandrene separately [6][7].

The pain data are rodent and consistent. Oral alpha-phellandrene at 3.125 to 50 milligrams per kilogram was antinociceptive in writhing, capsaicin, formalin, glutamate, and carrageenan hyperalgesia tests, without central depression, through mechanisms the authors traced to glutamatergic, opioid, nitrergic, cholinergic, and adrenergic systems [8]. In mice bearing Sarcoma-180 tumors, oral doses of 6.25 to 50 milligrams per kilogram reduced tumor growth by 47 to 83 percent and reduced mechanical nociception alongside improved oxidative and cytokine markers [9]. In an ifosfamide model of hemorrhagic cystitis, pretreatment reduced urothelial damage, myeloperoxidase, and tumor necrosis factor alpha [10]. These are low doses by terpene standards, but all are model results from a small number of groups, and none has been tested in people.

Natural sources

Phellandrene is an umbellifer and eucalyptus terpene. The systematic review names dill and fennel as sources reaching alpha-phellandrene levels up to 82 percent [5], and the (+) enantiomer is recorded in dill seed and shoot, bitter fennel, elemi, ginger grass, and turmeric rhizome, with Ridolfia oil at 85 percent [3]. HSDB adds Cymbopogon nardus at 16 percent of the plant, Norfolk Island pine, and jasmine [11]. Fragrance databases log alpha-phellandrene at 15.6 to 17.4 percent in Artemisia vestita oils, 2 percent in angelica root and seed oils, 1.7 percent in an Achillea flower oil, and traces in allspice, star anise, and basil [1]. Beta-phellandrene is angelica's terpene, at 61 percent of angelica seed oil and 16.7 percent of its carbon dioxide extract, with traces in ajowan, star anise, and bay laurel [4]. In cannabis phellandrene is a minor terpene, reported in a number of chemotypes at low levels.

Boiling point and vaporization

PubChem compiles alpha-phellandrene's boiling point as 175 °C from the Joint FAO/WHO Expert Committee on Food Additives [11]; fragrance references list 175 to 176 °C at 760 mmHg for alpha-phellandrene and 171 to 174 °C for beta-phellandrene [1][4]. This profile uses 175 °C (347 °F), the JECFA value for the alpha isomer, four degrees above the 171 °C the site previously listed, which corresponds to the beta isomer's range. That places phellandrene with limonene and the terpinenes in the volatile top-note band. Its instability is oxidative rather than thermal, and like alpha-terpinene it carries a conjugated diene: alpha-phellandrene is a ready hydroperoxide and epoxide former on air exposure, which is the chemistry behind its sensitizer classification. No thermal degradation study of phellandrene was found.

Safety and regulation

Alpha-phellandrene is listed by the US Food and Drug Administration as a permitted synthetic flavoring substance at 21 CFR 172.515, as "α-Phellandrene; p-mentha-1,5-diene" [12]. The Research Institute for Fragrance Materials assessed (−)-(R)-alpha-phellandrene in 2022 and beta-phellandrene in 2024 [6][7]. No cancer classification applies.

Its skin record follows the conjugated-diene pattern. Under Europe's classification inventory, effectively all notifications flag alpha-phellandrene as a flammable liquid, 96 percent as an aspiration hazard, and a further set as a possible skin sensitizer [11]. That sensitizer code, together with the diene chemistry it shares with alpha-terpinene, is the practical caution: fresh material is a weak sensitizer at most, oxidized material is the concern, and dill, fennel, and peppermint-eucalyptus oils that have been open for months are the exposure to avoid on skin.

Industries and uses

Fragrance: phellandrene supplies a green, peppery, dill-like top note in herbal, spice, and citrus accords and is stocked as alpha and beta isomers and as single enantiomers [1][2][3][4]. Culinary: alpha-phellandrene holds FDA flavoring status and is the defining green note of dill and a natural constituent of fennel, angelica, and black pepper flavor [1][5][12]. Aromatherapy: peppermint eucalyptus, dill, and angelica oils are its carriers; the oxidation and sensitization points above are the central caution for topical use of aged oils [6][11].