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Thread: Indole

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    Default Indole

    INDOLE
    ======

    Note : Base
    CAS Number : 120-72-9
    IUPAC Name : Indole
    Other Names : 2,3-Benzopyrrole, Ketole, 1-Benzazole
    Molecular Weight : 117.15079
    Vapor Pressure : 0.012200 [mm/Hg] @ 25.00 C
    Density : 1.17 [g/cm]
    Appearance : White to amber yellow crystalline solid powder
    Melting Point : 51-54 C @ 760.00 [mm Hg]
    Substantivity : 400 hours
    Relative Odor Impact : 250 / References: Iso E Super/Hedione (100); Ethyl Maltol (250); Furaneol (743)
    IFRA : No Listed (as of today)

    To My Nose:
    ==========

    Crystals 100% pure : Placing the nose directly over the container, amber indole's crystals smell like diluted naphthalene, it's a chemical aroma. After removing the nose from the container, the aroma persists in the olfatory system (which get "impregnated" by this molecula) and mutates; it turns unpleasant, (fecal) animal notes appear, non existent at the smelling moment. It can be somewhat repulsive. it's a sensation that goes down from the nose to the stomach and can stay there for hours. It doesn't seem to affect the perception of other odorants. Indole crystals are also quite diffusive; other person located in nearby rooms reported a strong smell to soiled diapers. However, the irradiated aroma (faecal) is different from that perceived smelling the container directly (chemical).

    5% w/w solution in ethanol applied on blotter : The effects are similar to those of pure crystals. When the nose is close to the blotter, a smell of diluted naphthalene is perceived, but in the air there is a fecal aroma. It's not a smell to human faeces, but rather it looks like fresh faeces of some dogs or horse dung. Obviously the experience is not pleasant.

    0.5% w/w solution in ethanol applied on blotter : At the first sniff it smells to mothball. It reminds me the fragrance I felt when I was a child taking a jacket out of the closet after many months of being there. Some minutes later, naphtalene aroma calms down and I can perceive a deeper smell on blotter, narcotic, heady, slightly reminiscent of jasmine. Aromas are not strong, but they do are deep and persist after removing the blotter from the nose. At this concentration, the solution is brown quite pale. Adding to the solution 4 small drops (0,028[ml]) of Hedione @10% (as softener), the harsh naphtalene smell at the exit decreases considerably.

    0.05% w/w solution in ethanol applied on blotter : Aroma seems weak at the first sniff, but it's deep and persistent; at the next day it's still on the smell strip... It's a base note. It may be associated with a floral aroma, but dark (narcotic, heady, lush, mesmerizing, addictive), not a "naive flower" at all. It's smooth, deep and round. It still smells a bit to naphtalene and solution is colorless. In some sense, it reminds me the dark side of jasmine. Just for testing purposes, adding 2 small drop (0,014[ml]) of Hedione HC @10% to 1[ml] of this solution sparks appear: Hedione HC intensifies the indol aroma; naphtalene aroma is more intense and notorious; however, overall, it smells closer to jasmine. Moreover, adding to the previous mixture 4 small drops (0,028[ml]) of classic Hedione @10%, it looks even more like jasmine. It seems to me that indole contributes to the dark and deep subnotes of jasmine while Hedione and Hedione HC impart some of the crisp (top-heart) subnotes.

    Update: Concentrations can be increased noticeably in a composition. It performs differently when alone or accompanied by other ingredients.

    Update: It behaves differently in skin than in blotter. Applied on the skin, in general unwanted nuances disappear after a few minutes, while on blotter they persist much longer.

    Update: Something that should be obvious to many perfumers, although it was not for me until now: One thing is how the perfumes smell from the substrate where they were applied and other thing is usually the irradiated aroma.

    Notes:
    =====

    The best indole perfumistic characteristics appear when it is sufficiently diluted. That threshold must be determined, but it is very likely that the maximum amount in the finished product be well below 0,5%. Above the threshold, the primary olfactory receptors of this molecule appear to be saturated, perhaps activating secondary receptors that send weaker or even distorted signals to the brain. This may explain that smelling directly from the blotter or the container the aroma is perceived as weak.

    Indole is very persistent. Some days after working with indole, I was testing Lyral and hydroxycitronellal. By chance I leaned the blotters on the same place and the samples of Lyral and hydroxycitronellal got impregnated with indole. At first I thought that these molecules could have some faint indolic characteristic; nevertheless I repeated the tests and it was not like that; they had simply become contaminated. By the way, a touch of indole does not hurt the combination Lyral / hydroxycitronellal.

    Both skatole and indole are present in human feces. Skatole is 3-Methyl-Indole and it smells more obnoxious (civet contains both indole and skatole). The aminoacid tryptophan is an indole derivative whereas skatole is produced from tryptophan in the mammalian digestive tract. The components responsible for fecal odor are complex and may be influenced by dietary and endogenous contributions. However, the major components are methyl sulfide compounds rather than skatole and indole.

    Indole is a fundamental compound in pollinators. Indole is occasionally a constituent of floral scent bouquets in nocturnal, moth-pollinated plants.

    For other part, in response to mechanical and herbivore damage, plants release a specific blend of volatile compounds, containing indole. These volatiles can affect herbivores in different manners by: i) Attractng natural enemies that feed on herbivores (predators and parasitic wasps) to locate their prey or host, ii) Signalling to other herbivores that the plant has initiated the production of deterrent compounds; iii) Signalling that herbivores are already present on the plant and its nutritional value is reduced, therefore helping to reduce additional herbivore damage, and iv) Function as anaerial priming agent to non-attacked neighboring plants, which will allow them to induce their defense mechanisms in preparation for future attacks. Moreover, indole serves as a precursor for toxic metabolites against herbivores.

    Even at low concentrations, indole can be somewhat repulsive for some people. This repulsiveness may not be manifested by smelling a fragrance occasionally, but yes wearing it everyday. Perhaps this aspect should be taken into account when developing mass commercial fragrances.

    More Info:
    ========

    https://en.wikipedia.org/wiki/Indole
    http://www.thegoodscentscompany.com/data/rw1006511.html
    https://www.perfumersworld.com/product/indole-9UN00235
    https://www.gastrojournal.org/articl...87)90262-9/pdf
    https://www.researchgate.net/publica...3737971_Indole

    Attachment 87817
    Last edited by gus.; 10th September 2018 at 11:36 AM.

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