There are many scents associated with Christmas time - the hot spiciness of cinnamon, sweet gingerbread or the nutty note of roasted chestnuts. The most characteristic aroma for me is one of Christmas tree and...oranges. Maybe because every year, I find these fruit in my Christmas stockings. Oranges, now in season, contain flavonoids, helping fight infections - it is the perfect winter gift. Still, there is an exciting connection between citrus fruits and Christmas trees. What do the citrus fruit and Christmas trees have in common?
Conifers' scent is distinct and characteristic only for some tree species. Most of the evergreen plants grown for Christmas trees are Silver fir (Abies alba) or European spruce (Picea abies) from the family of pine trees (Pinaceae) (1). Fir or spruce oil from the tree raisin - turpentine,
contains numerous terpenes that have recently gained more interest in the scientific world.
The lipid compound pinene is the most critical contributor to the Christmas tree scent. Its two forms (α- and β-pinene) can be found in many conifers, including juniper and pine, but also in lavender, eucalyptus and orange peel (2). While the α-pinene fragrance is close to turpentine, β-pinene has a more fresh and woody note (3).
Another compound that is present in orange peels and pine trees is limonene. Both terpenes occur in isomeric forms, and each isomeric state smells slightly different. But, most interestingly, limonene found in various conifers and fruits often accompanies α- or β-pinene and vice versa (4).
These compounds play a significant role in their hosts. They act as the first defence against plant pathogens - fungi, bacteria, viruses, and herbivores, making them an exquisite immune defence mechanism. Additionally, it has been shown that many terpenes have antioxidant properties, indicating their role in overcoming oxidative stress in plants (3,8,9).
If the terpenes play an essential role in plants, they may also benefit humans. There is an increasing number of studies developing methods to prove the beneficial effects of the
compounds on human health.
Preliminary research suggest that pinene can reduce inflammation and act as an antioxidant (5,6,10,11), and both forms of terpenes have been proven to be potent antimicrobial and antiviral compounds (7,9,12). It has been shown that pinene increased performance speed, decreased anxiety and improved mood (9,13). Additionally, pinene has sedative (helping with insomnia) and antidepressant properties, making them relevant candidates for novel, plant-derived medicines (10).
If you wish to elevate the levels of valuable terpenes but won't have a fresh and fragrant Christmas tree at home this year, you could prepare the orange pomander. This incense, including whole clovers, will make your home smell unique during the festive season. More importantly, it will enhance the vapour air with beneficial terpenes.
So, inhale the Christmas scents for better health and well-being!
References:
(2) Salehi B, Upadhyay S, Erdogan Orhan I, et al. Therapeutic Potential of α- and β-Pinene: A Miracle Gift of Nature.Biomolecules.2019;9(11):738. Published 2019 Nov
14.doi:10.3390/biom9110738
(3) Joanna Maria Kopaczyk, Joanna Warguła, Tomasz Jelonek. The variability of terpenes in conifers under developmental and environmental stimuli. Environmental and Experimental Botany 2020 Volume 180 104197, ISSN 0098-8472,
(4) Lou Reade. Festive fragrances. Chemistry and Industry. 19 Dec 2011; doi.org/10.1002/cind.7524_8.x
(5) Kim T, Song B, Cho KS, Lee IS. Therapeutic Potential of Volatile Terpenes and Terpenoids from Forests for Inflammatory Diseases. Int J Mol Sci. 2020 Mar 22;21(6):2187. doi: 10.3390/ijms21062187. PMID: 32235725; PMCID: PMC7139849.
(6) Cho KS, Lim YR, Lee K, Lee J, Lee JH, Lee IS. Terpenes from Forests and Human Health. Toxicol Res. 2017 Apr;33(2):97-106. doi: 10.5487/TR.2017.33.2.097. Epub 2017 Apr 15. PMID: 28443180; PMCID: PMC5402865.
(7) Petrović J, Stojković D, Soković M. Terpene core in selected aromatic and edible plants: Natural health improving agents. Adv Food Nutr Res. 2019;90:423-451. doi: 10.1016/bs.afnr.2019.02.009. Epub 2019 Mar 28. PMID: 31445600.
(8) Romón P, Aparicio D, Palacios F, Iturrondobeitia JC, Hance T, Goldarazena A. Seasonal Terpene Variation in Needles of Pinus radiata (Pinales: Pinaceae) Trees Attacked by Tomicus piniperda (Coleoptera: Scolytinae) and the Effect of Limonene on Beetle Aggregation. J Insect Sci. 2017 Sep 1;17(5):98. doi: 10.1093/jisesa/iex066. PMID: 29117373; PMCID: PMC5623050.
(9) Geraci A, Di Stefano V, Di Martino E, Schillaci D, Schicchi R. Essential oil components of orange peels and antimicrobial activity. Nat Prod Res. 2017 Mar;31(6):653-659. doi: 10.1080/14786419.2016.1219860. Epub 2016 Aug 18. PMID: 27535797.
(10) Weston-Green Katrina, Clunas Helen, Jimenez Naranjo Carlos. A Review of the Potential Use of Pinene and Linalool as Terpene-Based Medicines for Brain Health: Discovering Novel Therapeutics in the Flavours and Fragrances of Cannabis. Frontiers in Psychiatry 2021, Volume 12, ISSN 1664-0640; DOI 10.3389/fpsyt.2021.583211
(11) Kim DS, Lee HJ, Jeon YD, Han YH, Kee JY, Kim HJ, Shin HJ, Kang J, Lee BS, Kim SH, Kim SJ, Park SH, Choi BM, Park SJ, Um JY, Hong SH. Alpha-Pinene Exhibits Anti-Inflammatory Activity Through the Suppression of MAPKs and the NF-κB Pathway in Mouse Peritoneal Macrophages. Am J Chin Med. 2015;43(4):731-42. doi: 10.1142/S0192415X15500457. Epub 2015 Jun 28. PMID: 26119957.
(12) Rivas da Silva AC, Lopes PM, Barros de Azevedo MM, Costa DC, Alviano CS, Alviano DS. Biological activities of α-pinene and β-pinene enantiomers. Molecules. 2012 May 25;17(6):6305-16. doi: 10.3390/molecules17066305. PMID: 22634841; PMCID: PMC6268778.
(13) Satou T, Kasuya H, Maeda K, Koike K. Daily inhalation of α-pinene in mice: effects on behavior and organ accumulation. Phytother Res. 2014 Sep;28(9):1284-7. doi: 10.1002/ptr.5105. PMID: 25340185.