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Author: Subject: Piper Auritum Essential Oil Extraction
CycloKnight
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[*] posted on 4-9-2018 at 08:54
Piper Auritum Essential Oil Extraction


I couldn’t find much in the way of recent experimental data on the steam distillation of this herb, so thought I’d give it a try and post my results here.

This herb grows wild in Mexico and in some parts of the US, but where I live it needs to be kept indoors or in a greenhouse. Fish wrapped in a large leaf of Piper Auritum (and then wrapped in foil) and cooked either in the oven or BBQ makes a fine culinary dish, the safrole licorice flavour works so well. Definitely a worthy addition to the herb garden.

I’ve been growing this plant for years but only began propagating it early Spring 2018 and so now have around 25 medium sized plants in the corner of my greenhouse. After each leaf has been cut, it is layed on a flat surface to dry, and then placed into a sealed (air tight) 10L glass jar for storage. The leaves aren’t bone dry, but dry enough for curing therefore not so moist as to allow any mold growth, nor decomposition. Dry leaves will lose their volatile essential oil rather quickly if left in the open so its prudent to not over dry them prior to storage. I’m uncertain if the curing leaf produces any more oil, but the leaves do seem more aromatic after storage than their bone dried equivalents.
I measured the moisture loss for a single leaf at around 88%, give or take. Assuming 1:10 dry leaf to fresh leaf ratio is probably fine for most purposes. A saucer sized leaf (rather smallish by P. Auritum standards) of approx. 8 grams will dry to about a gram or just under. The larger leaves can weigh many times that.


The older leaves are cut, but never the newer shoots, and never ever cut the main stem. Piper auritum does not recover well from damage to the main stem, and doing so will quite possibly kill the plant.
I’ve tried propagating from seed but without success. Best means of propagation I’ve found thus far, is by taking cuttings and placing in soil or in a flood/drain hydroponics or aquaponics (with a clear plastic propagator lid placed over the cuttin(s)). These work quite well. Not in too much direct sunlight however, usual rules for cuttings apply. Within a week to 10 days, the cutting(s) should be rooted. The stems don’t like being wetted constantly, every time I’ve tried using an aerocloner, all the cuttings died due to stem rot.

The leaves for this test run were collected over several weeks.
Steam distillation of 280 g dry leaves, and 293 g fresh leaves added later.




For the steam distillation, I’m using a large pressure cooker, it has a metal sealing flange, so therefore no rubber seal that could absorb any any volatile oils. The internal dimensions are 15.25” wide by 19” high, so therefore many times oversized for this steam distillation run, but my only other pressure cooker has a rubber seal. No steam is forced through, this will just be a simple task of boiling the water and collecting the condensate. Only the leaves you see here were used for this steam distillation.


The leaves are just floating on the water, it isn’t as full as it appears in the image. Could easily fit in a couple kg or so of dried leaves, if need be.


(The 293g fresh leaves were only added later after 1 L condensate already collected)

Equipment setup for distillation, still (pressure cooker) is sat on a single electric kitchen hob, 1500W. Water condensor is the double jacketed type. Very simple and straightforward.
The towels are just insulation for efficiency, not necessary.


(The short clear rubber tube connecting the 10mm copper pipe to the still wasn’t affected by the oils in any obviously discernible way.)

Leftover solids from the steam distillation. Only about a shovel full.



Free oil that came over with the condensate.


This was siphoned off directly with a pipette, then the remaining condensate solvent extracted. In total only 3 litres of condensate were collected, there was only a little oil in the third litre so decided to call it quits. The first litre was extracted with toluene (just to try it), then the next two litres extracted with dichloromethane. Both seemed to work satisfactory. DCM separated out a lot quicker, toluene needed a lot of salt added, next time I won’t use the toluene.


About 1.5 ml of free piper aurium essential oil in an amber bottle, this came over with the second litre of condensate. The oil from the first litre of condensate formed a honey like oily coating on the bottom of the collection flask, but I didn’t take a photo unfortunately. The distillation proceeded quite smoothly without any observed frothing.



Toluene extractions on the left, DCM extractions on the right.


Evaporating the last of the combined toluene extractions.


Final yield, combined solvent extractions on the left, the free oil on the right.


The final yield is 4.8 grams of Piper Auritum essential oil. The main component is by far and quite unmistakably, safrole. To those familiar with it, its pungent aroma is quite distinctive.

Given that only 3 kg condensate were collected, and that there were some residues still in the RBF I wasn’t able to extract with the long glass pipette, I’d consider it a safe bet to round that up to 5g or more for yield estimates, but 4.8g is the isolated yield from this small test run.

The combined leaf mass (fresh and dried) was 315g Piper Auritum. Based on 4.8g oil, that works out to be 1.52% recovered oil from the dried leaf.
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morganbw
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[*] posted on 4-9-2018 at 09:44


Nice presentation. I had to google the plant as I was not familiar with it.
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CycloKnight
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[*] posted on 4-9-2018 at 23:53


I've always called it the Mexican Pepperleaf, but during a recent trip to Cancun I learned that a friend there knew this plant well, locally they call it Yierba Santa. His next door neighbor had it growing practically everywhere in the yard.

The leaves eventually grow back, so can be harvested perpetually. The downside is, a lot of plants are needed. On the upside however, with the right technique its easy to propagate to as many plants as needed.

I'm pleased to note this morning that the dark sediment in the solvent extracted oil has settled out at the bottom, and a light amber coloured oil remains. Saves me having to filter it.
The purpose of yesterday's test run was to get a feel for the process and expected yields. With the economy of scale and more steam I'm sure one could manage a yield of 1.7% essential oil, based on the mass of dried leaves. 17 g oil per kg dried leaves sounds about right. 2 or 3 kg per distillation run, even better.

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zed
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[*] posted on 6-9-2018 at 15:17


Interesting. I haven't heard much about this plant, since the demise of The Hive. Thanks for the update.

Synthetic approaches aside, a major source of Safrole is from the distillation of Hardwood trees. Trees that the world can ill afford to lose.

https://www.pri.org/stories/2009-08-30/harvested-make-ecstas...

I recall similar stories from Amazonia. Though, MDMA is actually probably not the only root of the problem. Heliotropin and Safrole, are used in large quantities, both in the manufacturing of flavorings and in insecticides. Sources are few.

There are a lot of native populations, that are broke-ass starving. So, anything that can be harvested to produce spot-cash-money, is at peril. The extinction of ancient rain-forest trees, means little to a guy who has hungry children at home.

Piper Auritum, is a sustainable crop.

[Edited on 6-9-2018 by zed]

[Edited on 6-9-2018 by zed]
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SWIM
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[*] posted on 6-9-2018 at 16:18


Are you planning to estimate the safrole content by congealing point as per Guenther, or have you got access something fancier for analyzing your oil?



Ebay says they need to get their hands on my bank account if I want to keep selling there.
This sounds like the best idea since putting ortho tricresyl phosphate in Ginger Jake.
I'm walking while I can still walk straight.




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CycloKnight
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[*] posted on 7-9-2018 at 03:45


Zed, that's precisely the motivation for this project. Rainforests are being devastated due to worldwide shortages of certain natural oils, it also annoys me when the local authorities destroy the seized oil rather than selling it on to fragrance & pharmaceutical industries. In my view they should never destroy these oils, and when they do, basic mathematics dictates more forests (elsewhere) will be damaged to satisfy the worldwide demand.

We are literally working to save rainforests here. Likewise if a practical (environmentally friendly) synthesis via eugenol could be devised.

SWIM, I still have a sample of Sassafras Albidum essential oil I purchased many moons ago, and this Piper Auritum oil seems nearly identical as far as I can perceive, if there is a difference in safrole content I doubt its by much of a margin. I do plan to have analysed once I have a larger sample to work with.
I ended up rinsing the RBF from the final evaporation with a couple ml of DCM to get the last few drops out, and then added to the final sample bottle so I suspect a congealing point measurement would be inaccurate due the solvent now, at least until the last of the DCM evaporates out.
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