Talk:Limonene/Archive 1

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Anyone know where limonene for industrial purposes comes from? I strongly suspect it's extracted from orange skins as a by-product of orange juice manufacture, but this is conjecture on my part. Malcolm Farmer 09:20, 22 Apr 2005 (UTC)

• so I looked up limonene manufacturers. Biggest one in the US is basd in Flarida, manufactures citrus oil. Solved. Malcolm Farmer 09:44, 22 Apr 2005 (UTC)
• simply googling limonene found me several very details information webpage. Wim van Dorst 22:17, 2005 Apr 23 (UTC).

Does anyone know why citrus oil is classified R65 in Europe while the main component limonene is classified R43+R38 for human health? I have not found any other major component of citrus oil (citral, citronellal, decanal, ...) classified as R65? --moliate 23:31, 23 November 2005 (UTC)

• The R65 classification is incorrect, the classification for cas 8028-48-6 or einecs 232-433-8 in the ecb database conflicts the one for dipentene. Especially for aquatoxic labelling this is a problem, hopefulle this will be resolved when GHS is applied.

Conflicting results on health issues

The article as it stands now provides a very one-sided and maybe even factually inaccurate picture of the health effects of (d-)limonene, as anyone can see when glancing over the wealth of studies that have been performed on the subject.

For example:

• Almost all studies mentioning limonene with respect to skin irritation refer to oxidized limonene only. Although limonene reacts eagerly with oxygen, natural sources of limonene such as fresh citrus peel also contain powerful antioxidants, which would lower their potential to cause skin irritation. Other sources of exposure such as cleaning agents which do not normally contain antioxidants and which are typically used for longer periods of time after production, would be more irritating. [1] [2] [3]
• While some studies have found skin and renal cancer enhancing effects in rodents, others have failed to establish such a link. [4] [5]
• Other studies found anti-tumor activity with respect to mammary cancer in rats. [6] [7] [8]
• Most interestingly, studies have suggested that limonene can cause regression of human skin, breast, gastric and pancreatic cancer. [9] [10] [11] [12] [13] [14]

So whether the net effect of d-limonene on human health is detrimental or even beneficial is at the present unclear. In effect, after reading the abstracts from the above-mentioned studies, I am inclined to believe that reasonable dietary doses from fresh (organic) citrus peel are probably the latter. Aragorn2 22:29, 9 June 2006 (UTC)

______________

A Google search turns up the fact that lemonene is used as cancer therapy (there are medical studies reporting it efficacy) and as at least temporary cure for Gastroesophageal Reflux Disease, though this seems to be mostly on alternative health sites. This means that lemonene has the distinction of being a potential carcinogen and a suppressant of cancer. I suggest the amount of information out there on both sides should at least be mentioned. It is being marketed for as anti-cancer agent and as an effect alternative to other Gastroesophageal Reflux Disease treatments. RStillwater (talk) 23:21, 11 December 2009 (UTC)

Lemonene is a different substance from limonene. Maproom (talk) 10:48, 12 December 2009 (UTC)

environmentally friendly conflict

this phrase: "Limonene is increasingly being used as an environmentally friendly alternative to mineral oils as a solvent for cleaning purposes, such as the removal of oil from machine parts, being more easily biodegradable than mineral oils"

conflicts with the EU labelling: R50/53: Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.

A substance classified as R50/53 is certainly not environmentally friendly.

"Limonene can be used to dissolve polystyrene, and is a more ecologically friendly substitute for acetone" As limonene is sensitizing too and more toxic than acetone, this is not true. Please note that acetone does not dissolve polystyrene, it only converts it to a slimy mass. --FK1954 (talk) 16:30, 6 September 2013 (UTC)

Environmental risks?

--64.131.184.193 06:23, 4 May 2007 (UTC) I came across this looking for an environmental way to kill ants, and it is indeed being marketed as that. And I have to say--it kills ants and seems to mess up their trails but not affect the colony. Does anyone know the long-term affects of using this for the environment? At what concentration does it affect aquatic animals?

Limonene and Cannabidiol

Limonene's structure is present in that of cannabidiol. shoul this be mentioned in the article —Preceding unsigned comment added by The Right Honourable (talk • contribs) 06:22, 6 September 2007 (UTC)

Limonene Exposed to Ozone

I read an article by the Calif. Air Resources Board claiming that Limonene, coming in contact with Ozone, quickly produces Formaldehyde. This was an article attempting to show the detrimental effects of Ozone producing air purifiers. Their other test prtocols and statments made me skeptical of their findings. They didn't even differentiate between d-Limonen or l-Limonene, etc. Any thoughts or conclusions out there about Limonene coming in contact with Ozone at 1ppm to .03ppm? Thanks, Larry —Preceding unsigned comment added by 149.101.1.119 (talk) 18:52, 11 March 2008 (UTC)

Ozonolysis of limonene - whatever form - should lead to formaldehyde as one product. You need more than ozone to get that reaction to happen cleanly, so in the lab dimethyl sulfide is usually added. But I can easily believe that the product of ozone + limonene would give an ozonide that could slowly release formaldehyde. As for the "quickly", I'm not too familiar with the practical aspects of ozonolysis, so I couldn't judge that. Walkerma (talk) 04:00, 13 March 2008 (UTC)

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Oranges and Lemons

I have read - which of course is no evidence of anything - that the two enantiomers of limonene smell of oranges and of lemons, I don't know which is which. If this is true, I believe it should be mentioned. Maproom (talk) 22:45, 9 January 2009 (UTC)

Yes, I have read too, in the book "Organic Chemistry" by Solomons and Fryhle (pg. 200-201 of the eight ed.) that one of the enantiomers of limonene smells like orange and the other smells like lemon... Can anyone help clarify this please? Filipalpg 04:20, 16 December 2009 (UTC)

I have seen the same thing in Solomons and it's false. D-limonene has a citrus aroma and is present in great abundance in both oranges and lemons. The L-enantiomer is much less common in nature and has a pungent pine smell. Here's a link: http://www.leffingwell.com/chirality/limonene.htm

Presumably, oranges and lemons don't have their same smell because their essential oils don't have the same components (or don't have the same proportion of components).

Meltyman (talk) 04:17, 21 March 2010 (UTC)

I have smelled pure samples of both enantiomers - and it is true that one enantiomer has an aroma which is very reminiscent of oranges and the other does smell more of lemons - this is not to say that lemons only contain one enantiomer and oranges only the other. The chemistds (talk) 10:34, 19 November 2010 (UTC)

I now have a reference for the claim that one enantiomer smells of oranges and one of lemons:

P.W.Atkins, Molecules, page 12, Scientific American Library, 1987. ISBN 0-716-75019-8

but I would prefer to leave it to a chemist to add this to the article. Maproom (talk) 20:22, 21 May 2012 (UTC)

'Organic Chemistry' by Clayden, Greeves, Warren and Worthers states that one enatiomer has a citrus smell and the other has a pine smell 86.46.107.242 (talk) 23:35, 4 September 2012 (UTC)

For sure, the article's sidebar shouldn't read "Odour: lemon", bur rather "orange". Limonene is present in nature (almost) only in the d- form, which smells very strongly of orange, as anybody who's had to do with it in its pure form can confirm. Also, when the essential oil is extracted by steam distillation from lemon zest, which should be around 65% limonene, it apparently smells of orange (see 6:45. Not something we can cite, but still… https://www.youtube.com/watch?v=kugobytGTzE). Aelwyn (talk) 19:07, 31 March 2016 (UTC)

Limonene as a carcinogen

I have removed the quote attributed to a Dr Sam Epstein. While it may be of passing interest that some medical professionals have not kept up to date with the classification of certain carcinogens, I feel that the very mention of this quote may appear to support evidence in opposition to the findings of IARC. Such evidence does not exist at the present time, and hence Epstein's comment appears to have been made in error.Jimjamjak (talk) 16:16, 7 January 2010 (UTC)

I do believe Limonene should not have the carcinogenic classification as stated by the IARC themselves. There was one study made on mice and rats and it was found to produce renal tubular hyperplasia and increased combined incidence of renal tubular adenomas and carcinomas in only the male rats. This is from binding d-limonene and 1,2-epoxide to an α2u-globulin. This type of globulin is also used to transport a variety of ligands and is incidentally synthesized in humans.

In relevance to humans "Saturable binding of d-limonene-1,2-epoxide to α2u-globulin can be shown in vitro, but other superfamily proteins, particularly those synthesized by humans, do not bind this agent (Lehman-McKeeman & Caudill, 1992b). The unique specificity of the syndrome of renal toxicity in male rats due to α2uglobulin is demonstrated by the lack of toxicity and of renal tumours in mice. Mice synthesize mouse urinary protein, which shares nearly 90% sequence identity to α2uglobulin; however, d-limonene-1,2-epoxide does not bind to the mouse protein and it does not produce a similar syndrome in mice. Additionally, the lack of a response in female rats, which synthesize many other proteins of the superfamily, demonstrates that these proteins are unlikely to contribute to renal toxicity."

And as a similarity "The protein content of human urine is very different from that of rat urine, as humans excrete very little protein (about 1% of the concentration found in urine of male rats)."

and

"Female rats synthesize less than 1% of the amount of α2u-globulin reabsorbed by male rats, but no α2u-globulin is detected in female rat kidney and female rats do not develop nephropathy. The most abundant α2u-globulin superfamily protein in human kidney and plasma is α1-acid glycoprotein, and this protein does not bind to agents that induce α2u-globulin nephropathy in rats."

I also find that this statement from the IARC should be sufficient "Taken together, there is no evidence that any human protein can contribute to a renal syndrome similar to α2u-globulin nephropathy, and thus no evidence that d-limonene is carcinogenic in humans by a mechanism similar to α2u-globulin nephropathy."

TL;DR It is one study on limonene. It binds to a globulin. Only male rats get kidney cancer. Humans can't because human body don't excrete it like male rats. Humans pee like female rats. Studying mice and rats teaches us more about mice and rats than it does about humans.SecretLars (talk) 20:48, 9 February 2022 (UTC)

References

Clearer representation of enantiomers

I'd like to suggest that the two enantiomers are more clearly described. Would it be acceptable to have separate chemboxes for the racemic, R, and S structures. As it stands at the moment I think that there is potential for confusion, with the chembox showing one enantiomer and then containing a mixture of different bits of information. I'm happy to make a start on this if it is an acceptable approach. The chemistds (talk) 10:41, 19 November 2010 (UTC)

Would be worrying if every article on a chiral compound had 2-3 chemboxes (R, S, rac, etc.) Should we just replace this image of an enantiomer by one with an undefined stereobond? --Rifleman 82 (talk) 00:12, 20 November 2010 (UTC)

Yes, this is a perennial problem. I don't like the idea of putting an undefined stereobond in the chembox because the natural type of limonene as normally found is optically active; however, it would be worth looking into how the name is used. I do know that the racemic form is usually referred to as dipentene, so that may confuse people; also, I remember how missing out stereocentres can lead to problems! But if the defined meaning of limonene can refer routinely to either isomer (as with carvone, where both isomers exist in nature), it may be OK.

BTW, I'm the person who did the biosynthesis scheme, which shows limonene in that fashion. I'm sure that I would have copied it from a book as written (probably one of Mann's books); if you need me to revise that let me know.

There is some precedent for using multiple chemboxes - Cresol has been that way for a long time. It's certainly less pretty than a single chembox in the corner. In most cases we've preferred to keep things in one chembox; the same has usually been true for hydrates (as with Chromium(III) chloride). Perhaps it would be best to try and just make this one chembox clearer? Any thoughts, chemistds? Walkerma (talk) 04:48, 20 November 2010 (UTC)

Article focus?

The article is overly focused on minor points or recentism, which could delude a serious reader seeking core information on this resource. I guess some of these entries reflect the hoping/searching for green/renewable resources. I also think that the safety section is inflated and could use a disclaimer to the effect that any unsaturated hydrocarbon hydrocarbon is a skin irritant. Again, this kind of editing is well-intentioned but potentially misleading.--Smokefoot (talk) 13:07, 16 June 2011 (UTC)

Formaldehyde

Today's Daily Telegraph, p.17, asserts that limonene reacts with atmospheric ozone to give hazardous formaldehyde. 94.30.84.71 (talk) 18:18, 20 January 2016 (UTC)

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Proper typography

I'm wondering about the proper typography surrounding the "d" in "d-limonene." Should it be a lowercase "d," a smallcap "ᴅ," or an uppercase "D"? Should it be italic or roman? I've seen mostly lowercase italic, but I would have thought a roman smallcap. Please advise. 70.26.183.201 (talk) 15:13, 22 December 2017 (UTC)

Convention is for the capital D which is taught in basic chemistry to be italicized, although common practice seems to have dropped this convention. I edited the article for consistency and added the thorough PubChem reference which uses the non-italicized cap D. --Zefr (talk) 16:29, 22 December 2017 (UTC)

Problems in the section Safety and research

The sentence "There is no evidence for efficacy or regulatory approval of perillyl alcohol – the precursor for D-limonene – as a chemotherapeutic agent.[12][13]" has four problems:

1. Perillyl alcohol is a metabolite of D-limonene, not a precursor – see for example, perillyl alcohol or https://pubchem.ncbi.nlm.nih.gov/compound/D-LIMONENE.
2. No evidence of efficacy? There are many research papers to the contrary, including some cited in references 12 and 13 at the end of the sentence, not to mention the clinical trial for its use in treating gliomas: https://www.ncbi.nlm.nih.gov/pubmed/30563210
3. Regulatory approval? Hey, if my liver needs regulatory approval to produce and use perillyl alcohol, it's time to storm the bastille.
4. This article is about limonene, not perillyl alcohol. The sentence is off-topic. I recommend deleting it.

I agree that the sentence is off-topic and I have now removed it. -- Ed (Edgar181) 22:26, 18 July 2019 (UTC)

chemical equation

I want to know what is chemical equation for limonene 113.211.133.144 (talk) 07:37, 15 January 2022 (UTC)

 7737 publications on limonene since 2020

So you want to highlight a wonderful super-important publication on limonene? Well, get in line: seven (7!) papers/patents/reports discussing limonene appear every day. Hence WP:SECONDARY. Here are some major reviews on the topic:

• "Progress in Renewable Polymers from Natural Terpenes, Terpenoids, and Rosin" Wilbon, Perry A.; Chu, Fuxiang; Tang, Chuanbing; Macromolecular Rapid Communications (2013), 34, (1), 8-37. https://doi.org/10.1002/marc.201200513
• Repellent activity of essential oils: A review" Nerio, Luz Stella; Olivero-Verbel, Jesus; Stashenko, Elena, Bioresource Technology (2009), 101, (1), 372-378. https://doi.org/10.1016/j.biortech.2009.07.048
• "Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects" Russo, Ethan B. British Journal of Pharmacology (2011), 163, (7), 1344-1364. https://doi.org/10.1111/j.1476-5381.2011.01238.x

--Smokefoot (talk) 16:39, 8 December 2022 (UTC)

Get smart ! https://pubmed.ncbi.nlm.nih.gov/?term=limonene%5BTitle%2FAbstract%5D&sort=date&filter=pubt.meta-analysis&filter=pubt.systematicreview Atchoum (talk) 16:50, 8 December 2022 (UTC)

Great approach! So now you appreciate the extent of the literature on this very well investigated chemical and perhaps cite reviews vs primary stuff. --Smokefoot (talk) 18:36, 8 December 2022 (UTC)