Pharmacognosy and Natural Products
This domain examines crude drugs and herbal medicinal products: botanical source, active constituent class, identification reactions, standardisation and the European regulatory route for herbal products. Questions frequently pair a drug name with its plant family, its marker compound or its chemical class.
The major constituent classes
- Alkaloids: nitrogen-containing, basic, extracted as salts. General precipitation reagents include Dragendorff (orange-red), Mayer (white) and Wagner. Examples: morphine and codeine (Papaver somniferum), atropine and scopolamine (Atropa belladonna, Datura stramonium), quinine (Cinchona), vincristine and vinblastine (Catharanthus roseus), colchicine (Colchicum autumnale), caffeine (Coffea, Camellia sinensis).
- Glycosides: cardiac glycosides digoxin and digitoxin (Digitalis lanata and D. purpurea) identified by the Keller–Kiliani reaction; anthraquinone glycosides in senna and aloe detected by the Bornträger reaction; cyanogenic glycosides in amygdalin.
- Terpenoids and essential oils: monoterpenes and sesquiterpenes, obtained by hydrodistillation or steam distillation and assayed by gas chromatography. Menthol (Mentha), thymol (Thymus), and the sesquiterpene lactone peroxide artemisinin (Artemisia annua).
- Phenolics: tannins, flavonoids and salicin (Salix species); silymarin from Silybum marianum.
Greek and pharmacopoeial specifics
- Greek aromatic flora is examinable: Sideritis species (Greek mountain tea), Origanum vulgare subsp. hirtum (Greek oregano), Salvia fruticosa (Greek sage), and Chios mastic from Pistacia lentiscus var. Chia, a protected designation of origin product.
- European Pharmacopoeia monographs define identity (macroscopic, microscopic, chromatographic fingerprint) and assay, often expressed as a minimum percentage of a marker constituent or of essential oil.
- Extracts are standardised by the drug-to-extract ratio (DER): a 4:1 dry extract means 4 g of herbal drug per 1 g of extract. Solvent composition (ethanol percentage) is part of the specification.
Regulation in the EU and Greece
Herbal medicinal products fall under Directive 2001/83/EC. The traditional-use registration requires at least 30 years of medicinal use, 15 of them within the EU, and permits only a traditional-use indication without a benefit-risk assessment of efficacy. Well-established-use dossiers are the alternative route. EMA/HMPC monographs supply the accepted quality and safety data; the EOF grants the national registration.
Worked example
A tincture is prepared 1:5 in 70% ethanol. How much herbal drug is represented by a 2 mL dose? A 1:5 tincture contains 1 g of drug per 5 mL, so 2 mL represents 0.4 g of drug equivalent. Reasoning: the ratio is a mass-to-volume relationship, so scale directly; if a 1:1 fluid extract were used instead, 2 mL would represent 2 g and the dose must be recalculated.
Traps that cost marks
Confusing Digitalis lanata with D. purpurea; assuming herbal equals harmless (St John's wort induces CYP3A4 and P-glycoprotein and can precipitate transplant rejection and contraceptive failure; ginkgo increases bleeding risk); mixing up% w/w and% v/v in essential-oil assays.