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I'm extracting piperine for use with curcuminoid supplements using a soxhlet apparatus and 91% isopropyl alcohol. My first extraction is right about done but I still need to do two more because of the limited size of my soxhlet.

My question is, instead of distilling off and reusing the distilled IPA could I just use the same solvent that contains the black pepper extract for three subsequent extractions?

I tried googling but could not determine if piperine is stable enough.

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  • $\begingroup$ According to pharmacyjournal.net/archives/2016/vol1/issue7/1-7-21 piperine is indeed subject to thermal decomposition, but the conditions indicated are different than yours (heating without solvent at 80°C for 2 hours). Maybe, in order to lower the exposition to high temperature, you could dry your IPA first, and use it absolute: that should also improve your extraction yield at the same extraction time of the azeotropic ipa. A TLC analisys could give you an hint on what is the best procedure, but I would run multiple extractions, followed by vacuum distillations $\endgroup$
    – user32223
    Commented Apr 22, 2018 at 20:33
  • $\begingroup$ Hint: in order to dry IPA you don't need a dehydrating agent. You just need table salt and a separation funnel in order to "salt it out". $\endgroup$
    – user32223
    Commented Apr 22, 2018 at 20:42
  • $\begingroup$ Thanks for the tip on salting out IPA! That will come in handy. I let the first extraction run for over six hours. The second and third extraction will both be done in 2 hours + about half an hour to distill off about 200 ml of excess IPA to be reused. I will compare the amounts of piperine after I've purified it and hopefully remember to announce my results here as an answer to my own question. $\endgroup$
    – user62840
    Commented Apr 23, 2018 at 16:24

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So, I promised to answer this question based on my experiences if I'd remember. And I did. Here we go:

I did three soxhlet extractions, each with 175 grams of black peppercorns.

The first extraction took 6 hours and the cycles were quite slow due to the vapor pathways of the apparatus not being insulated. The second extraction took 2 hours, again with an uninsulated apparatus. The third extraction also took 2 hours, but the cycles were much faster because I used aluminum foil for insulating the apparatus.

Each extraction used 400 ml of 99% isopropyl alcohol of which 200 ml was distilled off after extraction. Something to note is that this reclamation for the first run took at least two times as long as it did for the two later ones.

The yields were as follows: - Run 1: 8,6 grams of piperine - Run 2: 6,8 grams of piperine - Run 3: 7,5 grams of piperine

From this I concluded that with sufficient insulation, something like 3-4 hours could potentially provide the optimal efficiency and that the yields of piperine aren't significantly affected by prolonged periods of heating in an alcoholic solution.

I hope this write-up will help or be of interest to someone!

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