Limonene is a terpene and is found naturally in the skin of citrus fruits, including orange, lemon, lime and grapefruit.
Limonene is a colorless, liquid hydrocarbon, and is classified as a cyclic monoterpene with the molecular formula C10H16.
Limonene has 3 isomers:
- D-limonene, also known as (R)-limonene, (+)-limonene, is found abundantly in citrus fruits.
- L-limonene, also known as (S)-limonene, (−)-limonene, is found in pine needles and cones.
- DL-limonene, also called dipentene, is a mixture of D-limonene and L-limonene.
These limonene isomers are found in different amounts and ratios in various plants. The predominant form of limonene is D-limonene, which is present in nearly 98% of all citrus oils (Anandakumar et al, 2021).
D-limonene is the main constituent of cold-pressed essential peel oils from citrus fruits, including sweet orange, bitter orange, grapefruit, mandarin, lemon, lime and bergamot.
Orange essential oil contains ~ 95% limonene.
Mandarin essential oil contains ~75% limonene.
Bergamot essential oil contains ~ 45% limonene.
D-Limonene has a fresh, pleasant citrus aroma. However, the purer the D-limonene is, the less odor it has (Chiralt et al, 2002; Sell et al, 2004; Kvittingen et al, 2021).
Commercially, D-limonene is isolated from orange peel. The cruder the D-limonene is, the more impurities it contains, and the more it will smell like orange (Kvittingen et al, 2021).
Dry Skin Love Wild Orange Oil to Milk Cleanser contains wild orange essential oil, sweet orange essential oil and bergamot essential oil, which all contain D-limonene.
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Chiralt, A.; Martínez-Monzó, J.; Cháfer, T.; Fito, P. Limonene from Citrus. In Functional Foods, Biochemical and Processing Aspects; Shi, J., Mazza, G., Le Maguer, M., Eds.; CRC Press: Boca Raton, FL, 2002; Vol. 2, pp 169– 187.
Kvittingen L, Sjursnes BJ, Schmid R. Limonene in Citrus: A String of Unchecked Literature Citings? J. Chem. Educ. 2021, 98, 11, 3600–3607.
Sell, C. S. Scent through the Looking Glass. Chem. Biodiversity 2004, 1, 1899– 1920.