Pharmacognosy and Natural Product Pharmacy
Pharmacognosy here covers crude drugs and their constituents, the quality tests that authenticate them, and the Mongolian–Tibetan formula tradition that still supplies a large share of products on Mongolian shelves.
Classes and their markers
- Alkaloids (ephedrine in Ephedra, morphine in Papaver) are basic: extract with acid, basify, then partition into organic solvent.
- Glycosides: cardiac, flavonoid, saponin and cyanogenic types - careless drying allows enzymatic hydrolysis and loss of activity.
- Terpenes and essential oils (menthol, thymol) are volatile and recovered by steam distillation.
- Phenolics: tannins, coumarins, and glycyrrhizin from Glycyrrhiza uralensis, a plant of the Mongolian steppe. Local materia medica also uses Hippophae rhamnoides (sea buckthorn) oil and Rhodiola rosea root.
Identity and assay
Macroscopic and organoleptic check, then TLC or HPLC fingerprinting against a reference standard. Assay must be expressed on the dried-drug basis, so moisture is measured and subtracted.
Worked example
25.0 mg of powdered Ephedra is extracted into 50.0 mL. A 0.100 mg/mL ephedrine standard gives peak area 4500; the sample gives 3600. Concentration = 0.100 × (3600/4500) = 0.080 mg/mL. Mass = 0.080 × 50.0 = 4.00 mg. Content = 4.00/25.0 = 16.0% w/w. If loss on drying is 8%, the dried-basis figure is 16.0/0.92 ≈ 17.4%.
Traps
Reporting a marker compound as if it were the active constituent; ignoring moisture; accepting one TLC spot as proof of identity; missing adulteration or contamination by heavy metals, pesticides or aristolochic acid in substituted species.