Solvents Flashcards
To understand all the various solvents used in making herbal preperations
Name the 7 different solvents or “menstrua” used in herbal preparations
Alcohol, water, alcohol-water mixture, vinegar, wine, glycerine, and oil
What are the concerns related to the use of wine and vinegar as menstruums?
wine and vinegar contain other plant material and sometimes yeast that tends to change the chemical composition and therefore the qualities of the herbal extract in unpredictable ways.
This is particularly important when issues such as predictability, permanence, and control are important such as when considering the potency and toxicity of some herbs.
When is vinegar and wine contraindicated?
for use with very strong or toxic herbs that are dose specific. Or for the long term preservation of an extract
Which constituents are best extracted with cold water?
Cold water is a good solvent for plant constituents, such as sugars, proteins, albuminous bodies, gums, mucilaginous substances, pectin, tannins or plant astringents, plant acids, coloring matter, many mineral salts, many glycosides, some alkaloids, most all alkaloidal salts, and, to a slight degree, a hint of essential oils.
What are the advantages and disadvantages of using hot water as a menstruum?
Advantages:
- hot water allows for the more rapid extraction of plant material,
- it also swells and disintegrates the plant material, allowing for the extraction of starches and other constituents not readily soluble in cold water.
Disadvantages:
- hot water can destroy some chemical constituents.
- reduces shelf life as the heating process extracts material that separates out when the menstruum cools. either settling at the bottom or floating at the top as foam. This provides foods for organisms which reduces shelf and can potentially change the chemical composition. Which is why decoctions should be strained to remove the extraneous plant material in order to prolong its shelf life
What is the universal disadvantage of water as a menstruum?
It is not a preservative
during extraction, it also extracts enzymes (especially cold extraction) and it allows for the growth of molds, yeast, and bacteria, which alters the state of the extract
Water extractions only last up to two days
How can we preserve water extractions?
by freezing or adding a substance that prevents the multiplication of microorganisms and disables the enzymes, such as alcohol
Why is it that water often extracts water-insoluble constituents?
As plant matter becomes infused in water, it changes the solvent properties of water allowing water-insoluble constituents to dissolve in it
Which constituents dissolve in ethyl alcohol?
Ethyl alcohol is a good general solvent for extracting resins, balsams, camphors, essential oils, alkaloids and natural alkaloidal salts, glycosides, organic acids, chlorophyll, most coloring matter, nearly all the acrid and bitter constituents of a plant, un-crystallized, amorphous vegetable sugars, and one fixed oil: castor oil.
Which constituents do NOT dissolve in ethyl alcohol?
gums, mucilaginous substances, starch, albuminous materials, many mineral compounds, crystallized cane sugar.
Why is alcohol a good preservative?
alcohol paralyzes enzymes that are destructive to alkaloids and glycosides
prevents the growth of yeast, molds, other fungi, and most bacteria
prevents the breakdown of glycosides and sapponins due to water.
Which two solvents do alcohol mix well with?
Water and glycerin
What is meant by the negative strength of alchohol?
It means that alchohol is very selective in which constituents it will extract and which it will exclude.
We can use alchohol to exclude or expell certain constituents, like mucolage, albuminous matter, starch and gums, from an extract by adding a sufficient amount of alcohol to it
This is useful because, muculage, albuminous matter, starch and gums are often dificult to filter out of extracts and they tend to disturb solutions aswell as provide food for microbes which shortens the solutions shelf life.
How can we use alchohol to preserve an extract that contains alchohol insoluble components such as mucolage, without expelling it from the extract?
by adding only 18 to 20 percent alcohol.
What is the lowest volume of alcohol one can use to maintain its preservative function?
18 to 20 percent by volume
Which constituents are extracted by vinegar?
vinegar contains acetic acid which is a polar solvant and as such would extract most water soluble constituents.
Acetic acid is alos unparallelled at the extraction and fixing of alkaloids
When is vinegar the best menstruum to use?
When the activity of the medicine depends on specific alkaloids
alkaloids readilly binds with acetic acid to form alkaloidal salt that is soluble in water
What is vinegar?
vinegar is a dilute acetic acid derived from oxidized alchahol
Why did the pharmacists abandon vinegar as a menstruum?
because the amount of acetic acid in vinegar is variable and they needed a relaible way of producing dose specific medication from toxic plant.
What is glycerine?
The sweet fraction of a fixed oil, usually coconut oil.
What chemical family do glycerine belong to?
Chemically, glycerin belongs to the class of alcohol, and is termed glycerol or glyceric alcohol. However it is a tri-atomic alcohol and contains no ethyl alcohol or methyl alcohol which are di-atomic alcohols having dramatically different characteristics.
Glycerine has a sweet taste. Is it a sugar?
Glycerine is not a carbohydrate and contains no sugar and is absorbed and metabolized too slowly to effect blood sugar levels
Is glycerine safe for diabetics?
Yes
For who is glycerine particularly well suited?
For individuals who cannot tollerate alcohol and for children.
What kind of plant material is easier to extract with glycerine?
with plants that have relatively large amounts of ligneous (woody) fiber; water expands these gummy and/or glutinous materials far more than glycerin does
What is the name for an extract made with glycerine?
A glycerite
What is the relationship between glycerine, tannins, and alkaloids?
It reduces the precipitation between alkaloids and tannins, in a liquid solution, by absorbing the tannins, leaving the alkaloids free to be absorbed by the body
What does glycerin not do very well?
Glycerin will not dissolve or mix with resins or fixed oils, so it is not suitable for resinous or oily herb extracts.
And although it is a good solvent for a few alkaloids, it is generally inferior to water, vinegar, and alcohol for extracting most alkaloidal structures.
Glycerin does not extract volatile oils very efficiently, but it readily mixes with them and preserves them for a short time.
what is glycerine relationship with the skin?
When diluted with water or aromatic hydrosols, glycerin is demulcent and emollient, lubricating, soothing, and protecting to the skin and mucous membranes. When used undiluted, it acts as an irritant that arouses activity.
what are the 6 things that ethyl alcohol cannot extract?
Crystalized sugar Mucilaginous substances Starch Gums Albuminous substances Most Salts
What does Mucilaginous mean?
having a viscous or gelatinous consistency.
“a mucilaginous paste”
(of a plant, seed, etc.) containing a polysaccharide substance that is extracted as a viscous or gelatinous solution and used in medicines and adhesives.
