Medicinal compounds from plants Cheat Sheet

Selecting the approp­riate plant species known for containing the target compound.

Drying & grinding the plant material to increase surface area for extrac­tion.

Evapor­ating the solvent (using rotary evapor­ators) to concen­trate the extract, yielding a crude extract that contains a mixture of compounds.

Assessing the bioact­ivity of the isolated compounds through pharma­col­ogical tests to determine their potential medicinal properties

Diterpene alkaloid obtained from Aconitum species (250 species) aka monkshood & wolfsbane – considered Britain’s most toxic plant (an orname­ntal) Used at one time to treat trigeminal neuralgia (sudde­n/s­evere facial pain).

Aconitine & related structures are complex terpene esters & neurot­oxins acting on Na+ channels. No antidote available! Symptoms of poisoning include burning of the mouth & throat, abdominal pain, intense thirst, headache, slow pulse, paralysis, convul­sions, delirium & coma. Treatment would be sympto­matic.

Using solvents (e.g., water, ethanol, methanol or hexane) to dissolve the desired compounds. Solvent depends on nature of the compounds (polar vs. non-po­lar).

Soaking plant material in solvent at room temper­ature for long period

Repeatedly washing the plant material with boiling solvent

Separating specific compounds from the crude extract using techniques such as:

recrys­tal­lising desired compound from solution to increase purity

Removing solid plant material from the liquid extract using gravit­y/v­acuum filtration

Analysing the isolated compounds to confirm their identity & purity using various techni­ques:

mass spectr­ometry (MS)

infrared (IR) spectr­oscopy

Plants that are toxic & have no medicinal potential or not yet realisede.g., Hemlock water-­dro­pwort (aka deadman’s fingers) (Oenanthe crocata) – contains oenant­hotoxin – a polyyne compound; Death cap (Amanita phallo­ides) – contains amatoxins (peptides that inhibit RNA polymerase II that converts DNA to mRNA)