Limonene — the citrus terpene of cannabis
d-Limonene is a cyclic monoterpene with the molecular formula C₁₀H₁₆ and, after myrcene, the second most common terpene in many cannabis chemovars. Chemically it has two enantiomers; the (+) form dominates in citrus and cannabis. Outside the plant, limonene is concentrated in the peels of lemon, orange, mandarin and grapefruit — the main component of their essential oils. In Swiss batches, typical values range from 0.05 % to 1.6 % dry weight, with sativas such as Amnesia Haze, Super Lemon Haze or Sour Diesel reaching higher levels.
Bright, citrusy, orange-peel — limonene shapes many sativa chemovars and is linked to mood-lifting effects.
Aroma
The aroma is distinctly citrusy with orange peel, lemon zest and slight juniper bitterness. With pinene it turns fresh and piney; with caryophyllene you get a "peppered citrus". Below 176 °C the citrus note stays vibrant; above, it thins and leaves room for bitter secondary notes.
Occurrence
Limonene is produced in the trichomes alongside myrcene and pinene and is the second-largest GC-MS peak in many citrus-forward varieties. In Swiss pilot-project batches, CBD flowers from Lemon-Haze and Diesel families often show a limonene/myrcene ratio above 0.5. Storage and UV matter: under light, limonene oxidises to carvone and secondary products that clearly alter the fresh citrus aroma.
Effect
In the entourage context, limonene is associated with mood-lifting, anxiolytic and mildly stimulating effects (Lima et al. 2013; Sommano 2020). Animal studies show anxiolytic and antidepressant effects via serotonergic and dopaminergic pathways. Small human studies of pure d-limonene in depression suggest a mood benefit but are methodologically limited. Legal note: in Switzerland, cannabis with ≥ 1 % THC is a narcotic. CBD flowers below 1 % THC are legal; medical cannabis requires authorisation. Effect descriptions are not therapeutic claims.