Author Topic: Predicting alkaloid solubility  (Read 1179 times)

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  • Guest
Predicting alkaloid solubility
« on: July 29, 2003, 06:07:00 PM »
I have a somewhat rare alkaloid (strychnine) that I want to extract from a botannical source (S. ignatii), preferably using "common household materials", as I am in a foreign country on vacation, and chemical access is VERY limited here. I am thinking of doing an acid/base, with vinegar as the acid, hopefully forming some acetate salt.
The problem is this: Strychnine is damned near insoluble in anything-the best I have seen for the freebase is 1g / 150mL of chloroform, which I most certainly don't have. In water it is closer to 1g/L! The salts seem to be much more soluble, but it varies widely with salt. Common ones seem to be nitrate and sulphate. So this brings me to my questions:

first, does anyone happen to know the solubility of strychnine acetate in water?

and, in the somewhat unlikely case that they don't,

second, how does one go about calculating or predicting the solubility of an alkaloidal molecule, as salt or base?

Thanks in advance.


  • Guest
The Hive isn't a non-toxic, but a non-toxin site
« Reply #1 on: July 29, 2003, 06:50:00 PM »
This is not site about hideous toxins, which have no other use to the amateur than to do harm.


  • Guest
That is an opinion, not a fact
« Reply #2 on: July 30, 2003, 07:04:00 AM »
I have read as much literature as there is to find on the internet and my library, and as far as I can see, strychnine is not the monster people make it out to be.

1. The therapeutic index seems to be at least 20, according to the lowest LD quoted (around 15 mg). Active effects begin in the submilligram range. Better than alcohol, apparently.

2. Strychnine has useful effects. Apparently, it has nootropic (at least on rats) effect, and perhaps "psychedelic" properties. It is claimed to markedly sharpen the senses by its actions on the spinal cord. Strychnine is in the 1917 british pharmacopeia, and is still used in chinese and ayurvedic medicine. (carefully, of course)

Now, it seems very likely to me that you did not do any searching regarding this matter before applying bad karma. Please keep in mind that most of the drugs discussed on this entire board are considered "hideous poisons" by many people, in the same knee-jerk manner as you condemn strychnine. Why? Because "everybody knows its bad". Because it's used to kill people in movies and books. Because it is used as a poison. I call that overdose, and most of the drugs on this board will kill you just as dead when taken to excess, if not as impressively.

Please, check these facts. Make sure the world is as you think it is, before blasting others.

Now. For my other point. Maybe I wasn't clear enough in my post, or maybe you didn't read closely enough, but I was asking a GENERAL question. Strychnine is my alkaloid of interest at the moment, but I want to know how to take any given alkaloidal compound's chemical structure and calculate its solubility. Is this not worthy of discussion at the Hive? At least for me, I can anticipate coming across other compounds sufficiently rare or uncharacterised such that solubility data is not available. I would prefer to at least have a rough idea before setting up any type of extraction. If this is off-topic in the general chemistry forum, perhaps you could suggest a better place to put it?

Well, anyway, I am just a bit annoyed.
Today somebody insulted my favorite alkaloid. :P

By the way, the reason I asked is because I don't like eating unmeasured amounts of ignatius bean. It is very unscientific, and perhaps, as you pointed out...dangerous.



  • Guest
I stand corrected
« Reply #3 on: July 30, 2003, 12:26:00 PM »
I stand corrected, and your 'off topic' rating has been removed. I'm sorry for the relatively premature conclusion I drew about your intentions, but there has been a lot of posts like yours in the past where people have asked about toxins for no-good reasons.

Still, strychnine should not be experimented with by someone not being in possession of a milligram scale, and a lot of knowledge. The LD50 is not that high.

As for your question, the solubility of different amine salts are very hard to predict, due to reasons presented in the following thread:

Post 357689

(Osmium: "Solubility of compounds", Chemistry Discourse)


  • Guest
some information
« Reply #4 on: July 30, 2003, 04:59:00 PM »
From The Plant Alkaloids (



Strychnine and brucine occur most abundantly in nux-vomica seeds (Strychnos Nux-vomica, L.) and Ignatius beans (S. Ignatii, Berg.). Both drugs contain from 2 to 3 per cent, of alkaloids, of which about one-half is strychnine in the former and two-thirds in the latter, the rest being mainly brucine.


For the extraction of strychnine and brucine on a laboratory scale the finely ground Strychnos seeds may be mixed with slaked lime and made into a stiff paste with water. This is dried at 100°, powdered, and exhausted with boiling chloroform. From this the alkaloids are removed by agitation with dilute sulphuric acid, which is then filtered, excess of ammonia added, and the precipitate extracted with 25 per cent, alcohol, which dissolves the brucine and leaves most of the strychnine undissolved. The latter is purified by recrystallisation from alcohol, in which brucine is more soluble.


The base is slightly soluble in water (1 in 6,400 at 25°, 1 in 3,000 at 80°) or ether (1 in 5,500 at 25°), more so in 90 per cent, alcohol (1 in 110 at 25° or 1 in 28 at 60°), or benzene (1 in 150 at 25°), readily so in chloroform (1 in 6 at 25°).


Strychnine nitrate, B.HNO3, occurs in colourless shining needles, soluble in water (1 in 42 at 25°), alcohol (1 in 120 at 25°), or chloroform (1 in 156 at 25°); laevorotatory. The sulphate, B2.H2SO4.5H2O, forms colourless prismatic crystals, m.p. 200° (dry), and is soluble in water (1 in 31 at 25°), or alcohol (1 in 65 at 25°), less so in chloroform (1 in 325 at 25°). The hydrochloride, B.HC1.2H2O, forms colourless, efflorescent, trimetric prisms, soluble in cold water (1 in 35) or alcohol (1 in 80).

If these figures are reliable, strychnine and its salts are both more soluble than you had been lead to believe. Are you going to try to remove the brucine? Can you at least get alcohol? Are you positive that you can't get any other solvent and/or acid? Sometimes you just have to know where to look.


  • Guest
« Reply #5 on: July 30, 2003, 06:45:00 PM »
I can get alcohol, they love it here. Maybe it will just have to wait till I return to the mother ship ;)
Thanks for the info-I didn't see the info on the HCl before.
Maybe in hot alcohol I will extract. I do want to remove the brucine...from what I've heard, the ignatii bean is about 2/3 strychnine and 1/3 brucine, and brucine is supposed to be much weaker than, but similar to, strychnine in its effects. So it's probably OK to leave it in, but....

The alcohol wash was the best way I could think of. Brucine is monstrously soluble in alcohol, something like 1g in 5ml.
So it would be very easy to wash it right out, like that book said. That is one reason I was wondering about solubility, too--they are so similar, B and S, but widely varying in solubility.

Strychnos seeds are REALLY hard to find! Nux-vomica is easier, but I still had to have them shipped from india, the shipping cost more than the seeds...
Ignatii, well...Let's just say getting my hands on some required meeting famous people and learning a foreign language...
Seems because of their poisonous qualities, and the advent of Warfarin and other such "improved" poisons, strychnine is not trivial to find anymore. So if someone wanted a poison, surely something from apricot pits or perhaps a swollen meat can would be better?

Thanks, Rhodium, for the link...I'm sure you could have laid a UTFSE on me for that one...