Pharmacognosy: Plant Chemistry and Natural Products
Pharmacognosy tests natural-product chemistry and the Philippine crude-drug tradition: botanical identity, phytochemical classes, extraction, standardization, and evidence-based use of medicinal plants.
Core rules
- Major classes: alkaloids (nitrogenous, basic; Dragendorff and Mayer tests), glycosides (cardiac and anthraquinone), flavonoids, tannins, terpenes and essential oils, and saponins.
- Plant part and collection time affect constituents; adulteration and substitution are common quality failures.
- Extraction methods include maceration, percolation, decoction, and infusion; solvent polarity selects which constituents are extracted.
- Standardization uses marker compounds or bioassays; a marker is not always the active constituent.
- DOH-endorsed medicinal plants include lagundi for cough, sambong as a diuretic, akapulko as an antifungal, bayabas as an antiseptic, yerba buena as an analgesic, tsaang gubat for diarrhea, ampalaya for diabetes, bawang, niyog-niyogan, and ulasimang bato. Use the approved plant part and preparation.
Worked example
A dried leaf crude drug contains 0.40% w/w berberine by validated HPLC. A 250 mg capsule is labeled to contain 2.0 mg berberine. Crude drug needed = 2.0 mg / 0.0040 = 500 mg per capsule. If an extract is standardized instead, calculate against the extract marker content, not the crude drug.
Traps
Confusing common names; using the wrong plant part; treating a marker as proof of efficacy; ignoring extraction solvent; accepting false-positive alkaloid tests; assuming all natural products are safe or unregulated.