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Plant chemistry and how to go about extracting it.

February 27, 2021

Plants are fascinating things and before we go any further I want to clarify that this article will be referring to dried plants, the type of thing we typically extract and then add into cosmetics rather than plant parts that are harvested for their oils (essential and/or vegetable oils). You could also call these herbs although not all dried plants are classified as herbs just to confuse everyone and everything.

I never used to think that though. When I was younger while I did ‘like’ a few – those with interesting stories like the foxglove and its murderous intentions, the dandelion that makes us wet the bed or the dock leaf that soothes my skin, I mostly thought of plants en mass and saw them as dull, boring, sedentary things that didn’t move fast enough or do anything exciting. Background greenery that was just there to run through, breathe in, stroke and hug, fall into, get stung by, feed to animals or pick and arrange.

As I left primary school we moved to a house with a larger garden and ended up with a gardener. It was at this point I realised that gardens can be something I can control. I can dig stuff up, plant new things, watch it grow then feed it to our rabbits or let the dogs poop on it. It was usually one of those things.

By the time I got to university I had fallen back into a headspace of thinking of plants as mostly infuriatingly boring and painful. My science degree meant I was to spend what seemed like hours studying parts of plants under microscopes. This made my eyes sting, brain hurt and my body feel like it was spinning. I loathed drawing cell diagrams and memorising endless parts and cycles. I felt like it was all just pointless and borning.

But then time passed, life changed and I changed my relationship with plants again.

Plants are fascinating things and for a cosmetic chemist they are a veritable factory!

I made the table above and have to admit it’s not 100% complete but it is a good start. I use it in one of the classes I teach and would thank people very much if they didn’t rip me off by copying this at all but if you must I’d like at least $250 each and a reference please. I will then send you my reference lists and background thinking – the stuff I’m not going to go into detail about here.

A very broad summary of the type of chemistry found in plants that benefits the cosmetic chemist are:

  • Vitamins
  • Natural surfactants
  • Antioxidants (plenty)
  • Gums
  • Insoluble fiber
  • Soluble fiber
  • Minerals
  • Tannins (toning, astringents, colours sometimes)
  • Proteins
  • Amino Acids
  • Fats
  • Essential Oils (of course but we’re really talking here about dried or fresh plants including herbs)
  • Sugars
  • Biologically active button pressers (pain relief, stimulants, anti-inflammatories etc)

The number one question about plant matter I get asked in this context is ‘I’ve bought this powdered herb, how do I use it in my product’.

I am sure I’ve probably talked about this on this blog before but I’m not a big fan of trawling through my past work – my bad really, I’ve written some good stuff that I could probably learn from hahahahaaha. Anyway…

There are two ways of tackling that question in terms of arriving at an answer.

The first way is to think about what you want out of it – what are you looking to achieve in your product (benefit) OR what chemical you think is in there and that you want to extract OR (in the case where you just like the plant, have lots of extract to hand and just want to use it in some way) where do I start…

The second way is to go straight to a reference book to see what chemistry is in the plant and the part of the plant you have and then build upwards from there.

Whichever way you tackle this you will end up having to perform the same type of analysis which basically boils down to you Identifying the plant you have, how it has been prepared to now (dried, fresh, powdered, pre-processed maybe) and what part of it you have got. It is important to keep in mind that plants contain many different parts and each part will have a slightly different chemistry. If you get lost on this dig up a weed or something that you are happy to sacrifice and look at it yourself. The flowers are different to the fruit are different to the leaves are different to the stems are different to the roots etc. Ask yourself early and often if the plant and the part of the plant you have got has the capacity to deliver the action you wish it to? This can be quite difficult to work out but with patience it is possible.

Side Note, Wishful Thinking.

I don’t know how many times I’ve witnessed this cognitive process unfolding in the minds of the people I’m conversing with but there is nothing quite as powerful as a herbal extract for bringing out the wishful thinking in people. So many people have come to me and asked if they can put Kakadu Plum powder in oil (because they want to make an oil-only product). I tell them they could if they want but it probably won’t achieve anything on the skin as the chemistry that Kakadu plum is famous for is water, not oil soluble. The people then plead that they can infuse it for a long time under sunlight/ in a double boiler or whatever and I tell them that doesn’t change the situation much except for probably killing off whatever vitamin C is in the fruit…

Now I don’t know everything about everything and am willing to concede that should you try this you MAY end up extracting something from the Kakadu Plum extract but I am confident it won’t be vitamin C. While Kakadu plum is not just about vitamin C that is its strong suit and what it is heavily marketed as containing so doing this and then marketing your product as having Kakadu Plum present in a way that brings skin benefits is stretching the truth somewhat I’d say.

So what to do?

As a general rule of thumb your sanity check in the world of herbal extracts is the wider market. I say ‘general’ as there are always some outliers and special circumstances.

If you’ve always struggled to find the herb you want to play with as an oil extract but everyone sells it as an alcohol or glycerin extraction there’s probably a good reason, that being that’s what pulls the best stuff from the plant.

On that note, if you mainly see your herb of choice as an alcohol extract and you want to extract it in water, ditto. Alcohol has different pulling power to water and as such it can achieve different liquid extractions.

If you can buy your target herb as a glycerin extract you are probably in with a chance of making your own liquid extracts if that’s what you want to do. While it is actually fairly easy to make alcohol extractions too, alcohol is more expensive than water or glycerin, is also flammable (which may or may not be relevant depending on what you are doing) and is usually an indication that the plant chemistry is a bit harder to access. Glycerin and water, on the other hand, indicate that the plant matter yields its chemistry rather easily and as such, you should achieve at least something when trying to make your own extracts.

The table I put above shows some common solvents used to pull the chemistry from plants. The first big divide in plant chemistry is between water soluble and oil soluble chemistry. As I mentioned above, if the plant contains oil soluble chemicals that you want, you must extract it into oil OR in a way that pops the oil glands. At this point I realise that most people don’t have a clue about the chemistry of the plant they just acquired. If that’s the case make a note of the fact that this is important then either find a book on herbalism that identifies both plant chemistry and what that chemistry can do for the skin. It is very much like being a detective, you don’t have to know why someone did something, indeed you may not know that at all at the beginning, the key is to ask enough of the right questions to guide you onto the next step. If still in doubt this is where you could ask a chemist, herbalist or other qualified person.

At the top of the table is a row of blue boxes that indicate how polar the solvent is, the solvent being what the plant chemistry will dissolve into. Polarity is important in extraction chemistry as you are basically trying to coax the chemical from one spot to another. We do this by setting up a solvent solution that is welcoming to the chemical so it can naturally diffuse into it. I tell people to remember what happens when they place a tea bag or tea leaves into hot water. The water is the solvent, the tea is the herb. The water has the right polarity to pull the tea-chemistry through. Water is very polar, glycerin slightly less so, alcohol less again then oil largely non-polar. Knowing the polarity of the chemistry you are trying to capture is hard. That’s why I put the table together – to make that part a no-brainer.

As far as knowing how much plant material to put into how much solvent that is somewhat variable and actually less important in the first instance. Think again of making tea. You can make a cup of tea by putting one spoon of tea leaves into your strainer and pouring the water into your standard cup or you can make tea by using two spoons of tea into the same cup. You possibly could go to 3 or 4 but at some point it becomes obvious you are just wasting the tea. In short, there isn’t a ‘perfect’ herb/ solvent ratio but there is a range that gives you the best chance of getting something usable, this is typically somewhere between a 20:80 – 50:50 ratio of herb to solvent. In terms of temperature and time again, this can vary. Long brewing times are not a thing usually with glycerin, glycol or water extracts and by long I mean more than a couple of hours. Mostly you can just combine, mix and then start separating after a few minutes, especially if you are heating the solvent slightly (50-70C is usually enough depending on what you are aiming to extract). Heat basically gives the solvent more power while keeping its polarity the same so just as you make a rubbish cup of tea in cold water, you make a rubbish herbal extract in cold water often too, fruit powders and aloe being the exception.

And what about acids?

Some chemistry will yield better if the mixture is acidified first. The same can also be said about alkalising the solvent (mostly water in pH cases) but I didn’t add alkaline into the table as it can get a bit too complex for the audience I had in mind for this. For pH change we would typically use citric acid or sodium hydroxide solution, enough to change the pH to around 3 for acid or 10 for alkali. What pH change does to help is chemically alter the relationships that exist within the plant cells, un-gluing them if you like. The glued-up version is insoluble, the un-glued version being soluble (in your solvent). This can be useful with proteins and especially where you want to break those proteins down to more ‘digestible’ amino acids but as I said, that’s getting more complex.

A Final Note – Why Dry?

Most herbs we work with are pre-dried. This is because most plants contain a lot of water. Removing that leaves only the ‘other’ chemistry and it’s that we want. We are then free to customise our solvent without it being contaminated (as with oil extractions) or diluted by the water already present. So dry first then extract is a good plan.

The End.

I get that plant chemistry is hard to grasp but there is an easier way and that’s to just grab whatever plant you are interested in and just put some into different solvents – run your own experiment. Maybe store them for a day or so, shaking every so often and see what changes you can observe and measure. If you have the money you could always send them all off for analysis to see just what you pulled. Wow, now we are sounding like a millenials Friday night on Tinder…

Have fun, keep your mind open and don’t stress. Plants are fascinating things and it only took me forty something years to figure that out. Oh and if all of this sounds like too much of a faff then just buy the ready-made extracts, there’s nothing wrong with that.

2 Comments leave one →
  1. February 27, 2021 11:55 am

    I know these aren’t common mediums for cosmetic extractions, but they are used for herbal extracts and I’ve worked with them for years: raw honey and vinegar. I guess vinegar falls under the acidic medium category, hence highly polar. Honey would probably be more like glycerin since it is also a humectant. Thoughts?
    Great article!!!

    • RealizeBeautyEd permalink*
      March 2, 2021 5:09 pm

      Hi there,
      Yes honey and vinegar would be similar to the acid and glycerin I’ve mentioned but remember that honey is both polar and acidic. On top of that honey is a more complex solvent than straight-up glycerin or glycerin in water so rather than consider it an equivalent, I’d think of it as a solvent in its own right with its own strengths and weaknesses. People may also think of alcohol solutions like brandy or vodka (rather than laboratory ethanol in water) as solvents – in this case it would be fairly safe to assume these would perform almost identically to those using just lab alcohol and water solutions of equivalent strength.

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