Molecules Extracted in Tranquillity
Last night I couldn't sleep, so, I began to think about a remedy for insomnia, in case this problem becomes a recurrent nuisance. If you were thinking that, being a vicious pharmaceutical chemist, benzodiazepines would be my first choice, though, you'd be wrong.
Chamomile tea is well-known, all over the World, as a reliable antiinflammatory for the digestive tract: flowers of Matricaria Recutita, in particular, are full of substances, such as bisabolol and essential oils, with remarkable efficacy in the treatment of severe conditions (even irritable bowel disease).
Weirdly, here in Italy, this plant is massively (and almost only) used as sleep aid, while few people, believe or not, know about its role as spasmolytic for the intestine, like the rest of the World seems to ignore the importance of chamomile tea when it comes to calming your nerves.
So, in case you were wondering which technique I reckon to be the best, here's my hint: instead of doing like anyone else (having a cup of chamomile tea before going to bed), you, chemists, are supposed to extract either the terpenes and the flavonoids from the capitula of M. Recutita you'll certainly find in your kitchen: such a time-consuming procedure, it'll certainly make you fall asleep. If you can't find it, then, go out and get some: hey, I know it's 1:30 am but you're suffering from insomnia, aren't you?!
That's pretty much what we did in our lab course: the extraction of both types of active substances from the flower-heads of M. Recutita, followed by a mere qualitative analysis. No yields, today!
Approximately 1 g of dried capitula of Matricaria Recutita (German Chamomile) were crushed in a mortar. First, we set to extract the lipophilic molecules (terpenes), so, we extracted them using 20 mL of dichloromethane for each of the two separations.
However, this being a solid-liquid extraction, we didn't need a separatory funnel: what we did, instead, was to stir each time, for 20 minutes, the content of the 100 mL conical flask we were using. Dichloromethane became yellow and, in the end, was entirely collected in a round-bottom flask.
This solution was concentrated, using a rotavap, to 1 mL of a greenish oil. Meanwhile, the mobile phase for the TLC was prepared mixing 9.3 mL of toluene with 0.7 mL of ethyl acetate (93:7).
Once our oil was ready, we quickly loaded it on our silica layer, in order to prevent the terpenes from reacting with air (which would have turned the colour of the oil from green-yellow to blueish).
The layer was therefore spayed with a 5% sulphuric acid (ethanolic) solution (the acid catalyzes the following reaction) and, then, with a 1% vanillin ethanolic solution (predictably the carbonyls react with the carbocations yielded by the acid). We placed the layer in the stove at 100°C and exposed it to UV light ten minutes later.
I have to say I didn't do any of these operations, since my colleague began this experiment while I was busy getting some IR spectra of products we had yielded on previous days. Still, once she had finished the extractions, she handed me the conical flask with the capitula and I kicked off the second part of the experiment, while she went on with the terpenes.
I put all the capitula in a 100 mL round-bottom flask, added 30 mL of methanol and heated under reflux (80°C) for 15 minutes.
With some cotton in a funnel I transferred all the organic phase in a test tube: 2 mL of this methanolic solution were concentrated at a rotavap, yielding a first sample that should be rich in rutin.
The rest of the test tube was concentrated to 1 mL, as well. 5 mL of water and 1 mL of concentrated HCl were added in the hope to get quercitin only (simply breaking the glycosidic bond of rutin, using a strong acid).
I heated under reflux these reagents for 20 minutes (at 100°C), to increase the yield and added 10 mL of water.
I poured this solution in a test tube, where I also added 2 mL of ethyl acetate: amazingly, this liquid-liquid extraction is accomplished by simply shaking the tube, allowing the solvents to separate and, at last, decanting the organic phase. This procedure was done twice and the solution of ethyl acetate was dried, in the end, with sodium sulphate.
For the last TLC, given that our analytes are much more hydrophilic, a delicate emulsion had to be quickly prepared: ethyl acetate/acetic acid/water (100/22/27) were, in fact, chosen as the most suitable mobile phase for the job in hand. Terribly reactive, that's for sure.
Finally, I sprayed a 1% natural probe (which contains chlorogenic acid) ethanolic solution over the layer and some PEG (4000), so that yellow stains could be easily detected using fluorescence.
Good night!
