1. Collection & preparation of plant material
1. Collection & preparation of plant material: |
Selecting the appropriate plant species known for containing the target compound. |
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Harvesting the correct parts of the plant (leaves, roots, stems, etc) based on the phytochemicals of interest. |
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Drying & grinding the plant material to increase surface area for extraction. |
Isolating potential drugs from plants involves several systematic steps, dependent on the specific compound/class of compounds
4. Concentration
4.Concentration: |
Evaporating the solvent (using rotary evaporators) to concentrate the extract, yielding a crude extract that contains a mixture of compounds. |
7.Activity testing
7.Activity testing |
Assessing the bioactivity of the isolated compounds through pharmacological tests to determine their potential medicinal properties |
Poisonous Plants - Aconitine
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). |
Alkaloid content varies with growth stage Roots previously used for pain relief Roots have been mistaken for horseradish fatalities 5 mg considered enough to kill. |
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. |
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2. Extraction
2.Extraction |
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). |
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Common extraction method: |
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Maceration: |
Soaking plant material in solvent at room temperature for long period |
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Percolation: |
allowing solvent to pass through the plant material in column-like setup |
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Soxhlet extraction: |
Repeatedly washing the plant material with boiling solvent |
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Repeatedly washing the plant material with boiling solvent |
5.Purification
5.Purification: |
Separating specific compounds from the crude extract using techniques such as: |
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Chromatography: |
column chromatography, thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) to separate, identify & purify compounds |
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Crystallisation: |
recrystallising desired compound from solution to increase purity |
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Filtration/distillation: |
depending on chemical nature of compounds |
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3. Filtration
3.Filtration: |
Removing solid plant material from the liquid extract using gravity/vacuum filtration |
6.Characterisation
6.Characterisation |
Analysing the isolated compounds to confirm their identity & purity using various techniques: |
mass spectrometry (MS) |
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nuclear magnetic resonance (NMR) spectroscopy |
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infrared (IR) spectroscopy |
Poisonous Plants
Poisonous plants & fungi may be divided into 3 groups: |
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Plants that are undoubtedly toxic but have medical application in defined doses e.g., Deadly nightshade (Atropa belladonna) |
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Plants that are toxic & have no medicinal potential or not yet realised e.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) |
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Plants & fungi that are toxic & are abused for their hallucinogenic properties e.g., nutmeg & liberty cap (Psilocybe species) |
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