Alaskan Labrador Tea: Rhododendron Tomentosum. Uses, Research, Dosage, Safety, Health Benefits
Labrador Tea. Bog Tea. Hudson Bay Tea. Muskeg Tea. These are the most commonly used names for one of the most iconic and distinctive northern plants, Rhododendron Tomentosum and Rhododendron Groenlandicum.
We harvest Tomentosum approximately 100 miles south of the Arctic Circle and you can find it here: https://www.hyperborealherbs.com/shop/p/alaskan-labrador-tea-wild-foraged
Tomentosum is the main labrador of interior and northern Alaska, while Groenlandicum is both the main labrador to the south AND is typically but not always the specific labrador that most people think they are talking about. They are nearly identical to eachother with a few specific key differences that we’ll get into in a minute. Many people who will try to convince you that they are experts don’t know the difference between these two species.
Fun fact: rhododendrons, bearberry, azaleas, huckleberry and cornflowers, Labrador tea is a plant that belongs to the Ericaceae family.
I will confess that, despite its intoxicating aroma, I ignored labrador tea for years. When I first heard about it a long time ago, like many people, I was told that if you take too much you will get sick as it’s literally toxic. That is true, but there are some subtleties and details that I believe enable a safe and intelligent use of this somewhat contentious plant.
Traditional Uses of Labrador Tea:
Here is a very incomplete list of native peoples who have used labrador tea:
Algonquin
Inuit (and most if not all Indigenous Alaskan People)
Chippewa
Hesquiat
Kitasoo
Makah
Malecite
Micmac
Nitinaht
Saanich
shuswap
Like I said, this list is painfully incomplete. Maybe I’ll take some time later to add more to the list.
As far as native Alaskan traditional usage of labrador tea, this website will give you a pretty good idea of the most commonly described uses: https://alutiiqmuseum.org/medicinal-plants/narrow-leaf-labrador-tea
The big uses that stand out to me are for cold, flu, lung ailments, as a decongestant, energy, pain relief, and a general good, uplifting feeling. These to me are pretty hard to deny.
“Dena'ina Athabascan people report that this shrub is especially effective for “weak blood”, colds, and tuberculosis. It can also be used for arthritis, dizziness, stomach problems, and heartburn. The Dena'ina use Labrador tea as a spice for meat.” https://www.nps.gov/media/photo/gallery-item.htm?id=C2284E2C-1DD8-B71C-073273F99502192E&gid=C1BC7057-1DD8-B71C-077D4E849BEA9268
You might see the name “ledum” still given as the latin name for labrador but they are no longer officially considered ledums. You also might see it referred to bog or wild rosemary, but there is a different plant with pink flowers that is generally considered to be “bog rosemary”: Andromeda polifolia.
People on long trips were told to chew on Labrador and swallow the saliva to prevent thirst and lethargy.
“If someone has been gone from his home for a long time, when they finally arrive home, because their environment is different, something happens to them, they get sick. For that reason, you have to eat a little bit of soil when you arrive. That's what they used to tell us to do.” Excerpted from: Yungcautnguuq Nunam Qainga Tamarmi/All the Land's Surface is Medicine: Edible and Medicinal Plants of Southwest Alaska (Snowy Owl)
It was also famously used for smoke smudging.
“When we young ones would take baths, after taking baths, they would burn (dried ayut) and shake them over our bodies.”
“When they'd take a deceased person out of the house, they'd (purify) the home with ayuq. Did they do it to freshen the smell of the air or to take the spirit out? I don't know the real meaning of that, but that's what they used to do.”
“Following the custom of his ancestors, one who was going down to the ocean for the first time would light a fire, and after filling it with ayuq, after removing his belt, he would place heavy smoke all over the his body. Then after doing that, he would take his kayak and go through it, too. They say if he followed the tradition that was passed on from his ancestors, he would apprea bright to the persons of the ocean. Since our elders explained everything, they said one who was goingo down to the ocean for the first time is brightening himself so that the persons of the ocean wouldn't be offended by his appearance.”
“A person who cannot see or cannot catch although he hunts, they have him purify himself with ayuq smoke....
“Some say its smoke was like a shield to animals they hunted. Its smoke was like a barrier. If I cover my face, I cannot see this person although he's close. They say that's what they're like...When a person purifies himself with ayuq smoke, it's like the animals cannot see him.”
“These days, the priests still carry that out. They cannot be without it. They use it to cleanse, and when there are many people at church, they cleanse them and have the smoke take (impurities) away.”
(I need to find my sources for these quotes, I’m a little baffled about where they may be but I’ve read nearly a METRIC TON of material about Alaska and other subjects and my notes can become a little chaotic.)
Many people will be delighted to find out that it can also be smoked with other preferred smokable plants.
Some people say it can be hung up in closets to repel moths and I believe that is highly probable.
It is also thought to be anti-mutagenic and therefore possibly can help to prevent the formation of certain cancers.
DOSAGE, HOW TO PREPARE LABRADOR TEA:
Most people agree that you should always steep labrador tea, and not make a decoction. This is because if you make it too strong you will release a large amount of the more harmful compounds that could open the door for them to cause you an actual problem.
Some people say use no more than 2 leaves, 3 leaves, or 5 leaves, other people say 1 crushed teaspoon, 1 crushed tablespoon. I think a crushed tablespoon is the most I would ever attempt to brew. According to most sources your steep time should not exceed five minutes.
Side note: this plant is considered extremely unsafe for animals, and I would probably avoid letting children consume it as well (just my opinion).
You can make an ethanol extract (a tincture) and we will be listing one on our site as soon as the snow melts!
Many people also make topical preparations as it’s believed to have a few beneficial properties.
LABRADOR HERBAL TEA FOR LUCID DREAMING:
I can tell you from experience that labrador is a wonderful plant for inducing vivid and lucid dreams. There’s not necessarily ton of information or history about this, but it is an undeniable bonus with this plant.
Chemical Constituents:
This is a somewhat incomplete list:
Vitamin C
Catechins
Quercetin
Chlorogenic Acid
Para-Coumeric Acid
Pro-Cyanidins
Caffeic Acid
Rutin
Gallic Acid
Ursolic Acid
Kaempferol
TERPENES:
Ledol
Cyclocolorenones
Myrcene
Mimonene
Sabinene
Cymene
Thujenjal
Limonene
terpineol
bornyl acetate
ascaridole
palustrol
camphene
b-pinene
α-farnesene
n-tetradecane
hexadecanoic acid
oblivon c
lilac aldehyde
TRACE ELEMENTS (in order of concentration):
manganese
Aluminum
Iron
Zinc
Copper
Nickel
Vanadium
Lead
Molybednum
Thallium
Cadmium
It should be noted that the chemicals present, AND the amounts of these chemicals vary pretty wildly in the tomentosum species, AS WELL as by the region where these plants are grown.
As an example:
“The work by Schantz and Hiltunen included GC analysis of R. groenlandicum and R. tomentosum ssp. decumbens obtained from unspecified location in Alaska. The volatile fractions of both plants were dominated by germacrone (≥40%), a sesquiterpene constituent not found in substantial amounts in Eurasian specimens.”
What the heck is germacrone?
”Germacrone is a germacrane sesquiterpenoid that has formula C15H22O. It is a natural product found in traditional medicinal plants of the family Zingiberaceae. The compound exhibits a range of pharmacological activities including anti-inflammatory, anticancer, antiviral, anti-androgenic, antioxidant, antimicrobial, antifungal, neuroprotective and insecticidal activities. It has a role as a volatile oil component, an antiviral agent, an insecticide, an anti-inflammatory agent, an antioxidant, an antineoplastic agent, an apoptosis inducer, an autophagy inducer, an antimicrobial agent, an androgen antagonist, a neuroprotective agent, a plant metabolite, an antifungal agent, an antitussive, an antifeedant and a hepatoprotective agent. It is a germacrane sesquiterpenoid and an olefinic compound.”
How to Harvest:
People say all sorts of things about when and when not to harvest. In the spring, in the fall, not when in flower, and even when they are in flower. Many people steep the flowers themelves! Labrador is an evergreen plant so you can actually harvest it any day of the year. There ARE differences between different times of the year.
Here’s a little confirmation about the chemical difference in labrador at the time of flowering:
“The analyses of R. groenlandicum from Quebec, conducted by Belleau and Collin, confirmed the presence of germacrone, however, it was shown to be abundant only during the flowering period.”
https://www.sciencedirect.com/science/article/pii/S0367326X19317575#bb0085
Here is one of the only other examples that details the differences of chemicals present in labrador depending on the time of the season:
“There was significant seasonal variation in the quantity of all fifteen constituents assessed, whereas there was no seasonal variation of their total sum. The antioxidant activity was positively correlated with phenolic content and negatively correlated with daylight hours. The anti-inflammatory activity was negatively correlated with caffeic acid derivative 1 and daylight hours. Together these results demonstrate that the timing of harvest of R. tomentosum impacts the plant's phenolic content and its antioxidant and anti-inflammatory activities.”
https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0030-1270968
Some foragers have appropriated other culture’s spiritual practices when it comes harvesting (leaving a gift at the harvest site, etc), thanking the plant, but these are not necessary to do. Indeed, if the whole world is truly connected through consciousness as some people believe, I fail to see the necessity of imposing our human verbal language on a plant. In fact, I believe it to be an intensely arrogant and narcissistic practice particularly when carried out by modern people who also eat McDonalds. Ultimately, it’s all up to you. I’m probably going to write an essay on this subject as I think it’s one of the most noxious elements of western herbal communities.
As with most plants, only harvest what you need. Do your best to spread your pickings out over a number plants. Labrador is pretty widespread for now, and it would be nice to keep it that way.
Toxicity:
I can't speak for the whole world, but according to Alaskan Natives there is a limit to how much labrador tea you should use. The scientific research also agrees with this. Headache, nausea, and full on unpleasant hallucinatory states are possible. But for some reason, there are sooooo many people who try to downplay this basic fact. This may be due to the fact that rhododendron tomentosum is known to contain highly variable large amounts of the toxic compound ledol. Groenlandicum is found to have low amounts or none at all. In my mind, this would mesh well the polar opinions on what many people think is the same plant. You should be aware that one of the most consumed plants on Earth, hops, contain ledol as well.
Maybe you've seen the “Herbal Jedi” on youtube. He is a “second generation “master” herbalist”.
He has a video about labrador on youtube with almost 300k views. It’s possibly one of the longest and most viewed videos about labrador online anywhere.
In his own words: “...there's a bit of a toxic “tradition” with labrador”. Tradition?? I don’t understand why he bends over backwards to tautologically avoid stating a basic fact? It really makes no sense to me.
He says to not harvest while flowering “because that's “where the energy is””. Ok? What does that even mean? Is there perhaps a certain chemical he is referring to? Kinetic energy? Spirit energy? Electromagnetic energy? Caloric energy?
Rhododendron tomentosum and groenlandicum are considered to be mostly safe. A certain amount of grayanotoxin is easily broken down in the human body but when enough is consumed it will cause the famous symptoms of hypotension, nausea, confusion, diarea, headache, and things like that. Pretty much everyone will recover in 24 hours with no issues but it is very important to know that these plants are considered fatally toxic for many animals. Especially you already have a condition or disease that leaves you more vulnerable than the average person.
“Some people consider this to be a hallucinagenic plant”. Literally, his very next sentence is “it can put you in a coma.”
This is kind of similar to everybody’s generic descriptions. People very badly desire for anything natural to be 100% perfectly safe, but this is a fantasy.
Here’s another example of people avoiding the issue:
“People have long been drinking Labrador tea without obvious ill effect; it is a favorite of the Inuit and many of the Northern Canada First Nations people. The French Canadian fur traders used Labrador tea to extend their supplies of black tea. Common names speak to this history - Hudson Bay tea and trapper’s tea. It was also used medicinally - it is high in vitamin C and supposedly helps with a wide range of disorders - from migraines to hair loss to infections. The downside is that this plant contains a number of toxins.” -https://www.seacoastonline.com/story/news/local/2015/08/12/labrador-tea-its-effects-history/33692100007/
In my opinion, you should be able to say something is definitively, 100%, capable of causing serious harm if misused or misunderstood. I fear that most people will read “it’s safe” in the first sentence and then tune out after that.
Herbal Jedi goes on to encourage people to think of labrador as a plant to “move your energy” and to “move your chemistry”. What?? Where are we moving it to? Utah?
He says “don't think of this as an all the time drink. But myself, I drink this literally every day during the winter (but just one cup).” Again, you will be told one thing and then in the same breath something completely opposite. How do we even know if he really does this? I mean, do you know any olympians or 100 year old people that do this? Is it even necessary?
He says it will “sedate the stomach”. Sedate....the stomach? Right after this he says too much of this tea can “upset the stomach”. He says it is a laxative but also constipates you. Confused yet? Me too. The literature suggests that too much always acts as a laxative, Im not sure where he got the constipation thing from.
He also recommends this plant for hangovers. (he strangely doesn’t have anything negative to say about drinking that much in the first place).
And for gallstones, and for kidney stones. It “transorms what our body no longer “needs””.
It just sounds to me like him and others are just casting their net as wide as possible to convince as many people as possible that this plant will do almost everything for them.
I bring the things that he says about labrador up in this post because I want to encourage everyone to think for themselves and not accept the current low standards of quality and accuracey when it comes to people sharing information about plants.
The French Canadien authors of “foret” apparently also state that there is no conclusive evidence for the toxicity or that this only happens to people who use ridiculous amounts.
Perhaps you've heard of the famous “mad honey” which is infused with a toxic rhododendron. Well guess what, labrador is a cousin to this plant. Rhododendrons are strong plants and require mindfulness and tact when preparing them.
Grayanotoxin Poisoning: Mad Honey Disease and Beyond
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404272/
https://en.wikipedia.org/wiki/Grayanotoxin
I don’t believe that tomentosum or groenlandicum contain a significant amount of grayanotoxin like their famous cousin.
I think most people are aware that most people are highly susceptible to thinking “more is better” with just about anything. So imagine a person who thinks that, being eloquently told that “there is no evidence of toxicity” in a plant that literally is considered toxic. I think that’s a recipe for disaster.
Another toxic compound that is established to be present in Alaskan labrador plants is called ledol: https://en.wikipedia.org/wiki/Ledol
Some studies in Lithuania and Russia have shown that the proportion of ledol in the essential oil from R. tomentosum varied by a factor of ten, i.e. from 3.9% ledol to 30.5% ledol.
By contrast R. groenlandicum collected in the region of Chicoutimi, Quebec contained no detectable ledol.
I hope this post has provided you with some insight, some information, and some good starting points for your own research into this famous plant. Below are some links to the scientific research regarding both tomentosum and groenlandicum.
LABRADOR TEA SCIENTIFIC RESEARCH:
Rhododendron tomentosum (Ledum palustre). A review of traditional use based on current research
https://www.sciencedirect.com/science/article/abs/pii/S0367326X13000166
Rhododendron tomentosum Harmaja (previously: Ledum palustre) is a fragrant evergreen shrub found in peaty soils in northern Europe, Asia and North America, commonly referred to as wild rosemary, marsh tea, marsh rosemary or northern Labrador tea. At least since the eighteenth century it has been used in ethnomedicine for the treatment of various ailments, such as rheumatism, cough, cold and insect bites, as well as a repellent. The essential oil of wild rosemary with the rich polyphenolic fraction possesses analgesic, anti-inflammatory, antimicrobial, antiviral, antifungal and insecticidal potential, demonstrated by in vivo and in vitro studies. In addition, recent scientific research reported the promising antidiabetic, antioxidant and anticancer properties. This review summarizes the information concerning taxonomy, botany, ecology, chemical composition, biological activities, toxicology and traditional and contemporary application of Rhododendron tomentosum plants.
Ethnobotany in the New Europe: People, Health and Wild Plant Resources
Chapter 13 Norway's Rosmarin (rhododendron tomentosum) in Past and Present Tradition.
by Torbjorn Alm and Marianne Iversen
Labrador tea (Rhododendron groenlandicum) attenuates insulin resistance in a diet-induced obesity mouse model
https://pubmed.ncbi.nlm.nih.gov/25916863/
Purpose: Using a diet-induced obesity (DIO) mouse model, we investigated the antidiabetic effect of Labrador tea [Rhododendron groenlandicum (Oeder) Kron and Judd], a beverage and medicinal tea used by the Cree Nations of northern Quebec.
Methods: C57BL6 mice were divided into five groups and given standard chow (~4 % of lipids) or high-fat diet (~35 % of lipids) for 8 weeks until they became obese and insulin resistant. Treatment began by adding the plant extract at three doses (125, 250 and 500 mg/kg) to the high-fat diet for another 8 weeks. At the end of the study, insulin-sensitive tissues (liver, skeletal muscle, adipose tissue) were collected to investigate the plant's molecular mechanisms.
Results: Labrador tea significantly reduced blood glucose (13 %), the response to an oral glucose tolerance test (18.2 %) and plasma insulin (65 %) while preventing hepatic steatosis (42 % reduction in hepatic triglyceride levels) in DIO mice. It stimulated insulin-dependent Akt pathway (55 %) and increased the expression of GLUT4 (53 %) in skeletal muscle. In the liver, Labrador tea stimulated the insulin-dependent Akt and the insulin-independent AMP-activated protein kinase pathways. The improvement in hepatic steatosis observed in DIO-treated mice was associated with a reduction in inflammation (through the IKK α/β) and a decrease in the hepatic content of SREBP-1 (39 %).
Conclusions: Labrador tea exerts potential antidiabetic action by improving insulin sensitivity and mitigating high-fat diet-induced obesity and hyperglycemia. They validate the safety and efficacy of this plant, a promising candidate for culturally relevant complementary treatment in Cree diabetics.
Keywords: AMPK; Diabetes; GLUT4; Labrador tea; Natural health products; SREBP-1.
Therapeutic effect of Northern Labrador tea extracts for acute myeloid leukemia: Anti-AML Efficacy of Northern Labrador Tea Extracts
Acute myeloid leukemia (AML) is an aggressive hematological malignancy that is one of the more common pediatric malignancies in addition to occurring with high incidence in the aging population. Unfortunately, these patient groups are quite sensitive to toxicity from chemotherapy. Northern Labrador tea, or Rhododendron tomentosum Harmaja (a.k.a. Ledum palustre subsp. decumbens) or “tundra tea,” is a noteworthy medicinal plant used by indigenous peoples in Alaska, Canada, and Greenland to treat a diversity of ailments. However, laboratory investigations of Northern Labrador tea, and other Labrador tea family members, as botanical sources for anticancer compounds have been limited. Utilizing an AML cell line in both in vitro and in vivo studies, as well as in vitro studies using primary human AML patient samples, this study demonstrated for the first time that Northern Labrador tea extracts can exert anti‐AML activity and that this may be attributed to ursolic acid as a constituent component. Therefore, this medicinal herb holds the potential to serve as a source for further drug discovery efforts to isolate novel anti‐AML compounds.
Chemical variability of Rhododendron tomentosum (Ledum palustre) essential oils and their pro-apoptotic effect on lymphocytes and rheumatoid arthritis synoviocytes
Rhododendron tomentosum (Ledum palustre) is an aromatic plant traditionally used for alleviating rheumatic complaints which makes it a potential candidate for a natural drug in rheumatoid arthritis (RA) treatment. However, the effects of plants' volatiles on apoptosis of synovial fibroblasts and infiltrating leucocytes of RA synovia, have not been reported. Volatile fraction of R. tomentosum is chemically variable and chemotypes of the plants need to be defined if the oil is to be used for therapeutic purposes. In the presented work, cluster analysis of literature data enabled to define 10 chemotypes of the plant. The volatile fractions of known composition were then tested for bioactivity using a RA-specific in vitro models. Essential oils of two wild types (γ-terpineol and palustrol/ledol type) and one in vitro chemotype (ledene oxide type) were obtained by hydrodistillation and their bioactivity was tested in two in vitro models: I - peripheral blood lymphocytes of healthy volunteers and II - synoviocytes and immune cells isolated from synovia of RA patients. The influence of oils on blood lymphocytes' proliferation and apoptosis rates of synovia-derived cells was determined by flow cytometry. Dose-dependent inhibitory effect of the serial dilutions of R. tomentosum oils on proliferation rates of blood lymphocytes was found. At 1:400 dilutions, all the tested oils increased the number of necrotic cells in synovial fibroblasts from RA synovia. Additionally, increased proportions of late apoptotic cells were observed in leucocyte populations subjected to oils at 1:400 dilution.
Ascaridole-rich essential oil from marsh rosemary (Ledum palustre) growing in Poland exerts insecticidal activity on mosquitoes, moths and flies without serious effects on non-target organisms and human cells
Marsh rosemary (Ledum palustre, Ericaceae) has been widely used in the traditional medicine of various regions worldwide, and as insect repellent. Little is known on its essential oil (EO) insecticidal potential. This study explores the insecticidal effects of the EO obtained from L. palustre growing in Poland on selected insect pests and vectors. EO GC-MS analysis evidenced an uncommon chemotype characterized by ascaridole (35.3% as sum of cis-ascaridole and isoascaridole) and p-cymene (25.5%). The EO was effective against Culex quinquefasciatus, Spodoptera littoralis and Musca domestica, showing LC50/LD50 of 66.6 mg L−1, 61.4 μg larva−1 and 117.2 μg adult−1, respectively. It was not toxic to non-target Eisenia fetida earthworms and moderately toxic to Daphnia magna microcrustaceans, over the positive control α-cypermethrin. The EO cytotoxicity on human keratinocytes and fibroblasts showed high IC50 values (71.3 and 84.4 μg mL−1, respectively). Comet assay data highlighted no DNA damages. Based on our findings, this EO characterized by the ascaridole/p-cymene chemotype could be a candidate for the formulation of botanical insecticides; large-scale production of green insecticides by this rare species may be assured by ex situ cultivation and biotechnological techniques.
Evaluation of extracts and oils of tick-repellent plants from Sweden
https://resjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2915.2005.00578.x
Leaves of Myrica gale Linnaeus (Myricaceae), Rhododendron tomentosum (Stokes) H. Harmaja (formerly Ledum palustre Linnaeus: Ericaceae) and Artemisia absinthium Linnaeus (Asteraceae) were extracted with organic solvents of different polarities and the essential oils of leaves were obtained by steam distillation. The extracts or oils were tested in the laboratory for repellency against host-seeking nymphs of Ixodes ricinus Linnaeus (Acari: Ixodidae). Rhododendron tomentosum oil, 10%, diluted in acetone, exhibited 95% repellency.
Composition of young and aged shoot essential oils of the wild Ledum palustre L.
Ledum palustre (Ericaceae) plant preparations have been used for healing different pains, wounds, lung and other diseases from ancient times. Scientists have revealed that the antitussive and expectorant effect of L. palustre essential oils depends on the content of the sesquiterpenoid ledol. The preparation of the cough medicine “Ledin” was based on the above investigations. The L. palustre essential oil from Siberia inhibited the growth of other plants. A tick-repellent effect was observed for L. palustre (new name Rhododendron tomentosum (Stokes) H. Harmaja) essential oil from Sweden with the dominant constituents myrcene and palustrol
Trace elements in Labrador Tea (Rhododendron groenlandicum): How predominant sources to the plants impact the chemical composition of hot water extracts
https://www.sciencedirect.com/science/article/abs/pii/S0013935120301651
Labrador Tea (Rhododendron groenlandicum) has been an important food and medicinal plant to First Nations communities in North America for millenia, but little is known of its geochemical properties. Using plants from 10 sites in 4 provinces, including pristine and industrial regions, and employing the metal-free, ultraclean SWAMP laboratory facilities and procedures, we provide an estimate of the natural abundance of trace elements in the leaves, and the extent of their release during hot water extraction.
Composition of the essential oil of the Rhododendron tomentosum Harmaja from Estonia
https://www.tandfonline.com/doi/abs/10.1080/14786419.2014.907287
Wild Rhododendron tomentosum Harmaja shoots were collected from four localities of Estonia. Essential oils, isolated from dried samples by simultaneous distillation and extraction, were analysed using GC-FID and Gas chromatography–mass spectrometry methods. The yields of oils were in the range 0.14–0.87%. A total of 72 constituents, accounting for over 95% of the total oil yield, were identified. The major components in the all four oils studied were palustrol (15.9–53.5%), ledol (11.8–18.3%), γ-terpineol (0–31.2%), p-cymene (0.1–13.9%), lepalone (0.7–6.5%), lepalol (1.0–6.5%) and cyclocolorenone (1.0–6.4%). Two different chemotypes of R. tomentosum were found in Estonia and one of them was rich in palustrol (41.0–53.5%) and ledol (14.6–18.3%). The second chemotype, for the first time, was rich in γ-terpineol (24.7–31.2%) and contained less of palustrol (15.9–16.7%) and ledol (11.8–12.8%), but more p-cymene (12.5–13.9%). Also, γ-terpineol was identified for the first time in the oils of R. tomentosum.
Comparison of the Chemical Compounds and Antioxidant Activities of Essential Oil and Ethanol Extract from Rhododendron tomentosum Harmaja
https://www.tandfonline.com/doi/abs/10.1080/0972060X.2017.1377116
A comparative analysis of chemical compounds found in essential oil and ethanol extract from Rhododendron tomentosum Harmaja was conducted in this study. The major volatile components were identified as 4-thujene (27.05%), α-thujenal (12.24%), and (-)-4-terpineol (9.78%) in the essential oil. The contents of total flavonoids and total phenolics in the raw material were 37.9 mg rutin equivalent/g and 4.2 mg gallic acid equivalent/g dry matter, respectively; the contents of ursolic acid, hyperoside, quercetin, and kaempferol were 15.2, 1.29, 0.32, and 0.03 mg/g, respectively. The volatile components in ethanol extract contained α-farnesene (8.35%), n-tetradecane (6.37%), hexadecanoic acid (6.14%), oblivon c (5.89%), and lilac aldehyde (4.85%). Ethanol extract exhibited higher antioxidant capacities than essential oil, which were evaluated by DPPH assay and ABTS assay.
