Medicinal Plants: History and Biochemistry

Medicinal Plants: History and Biochemistry

• Plants have been used medicinally for over 5,000 years, providing various pharmaceutical agents (hormones, antibiotics, narcotics, antihistamines) and substances (hallucinogenic, poisonous, pesticidal).
• Early societies used plants to treat common ailments like pain, fever, and wounds.
• Examples include ephedra (amphetamines) and opium poppy (morphine, codeine).
• Early pharmacopoeias (herbal books) emerged in Egypt, Arabia, China, and Europe.
• The doctrine of signatures (plant appearance indicates healing properties) was prevalent.
• Many modern medicines are plant-derived; this is often more cost-effective than synthesis.
• 80-100 plant genera are used in modern Western medicine, with many in other cultures.
• 25-30% of Western medicines are based on plant chemicals (higher if microbial products included).
• Global trade in medicinal plants reached $30 billion (2002).
• Before the 1950s, over 80% of Western medicine was plant-based.

Plant Biochemistry

• Medically active chemicals are mainly secondary plant products (often defenses against herbivores).

• Secondary products also serve to attract pollinators and fruit dispersers.

• Plants lack excretory systems; these products help neutralize waste and toxins.

• Three main groups of medically significant secondary products are:

• Alkaloids: Nitrogenous ring compounds that affect the central nervous system (e.g., caffeine, morphine, quinine, strychnine, nicotine).

• Terpenoids: Two or more isoprene units (e.g., essential oils, cardiac and steroidal glycosides).

• Phenolics: Aromatic rings with hydroxyl groups (e.g., plant pigments, poisons, medicinal drugs).

• Plant medicines have been introduced into modern research via traditional medicine (e.g., calabar bean for glaucoma treatment).

• Early poisonous plant extracts have proved beneficial in moderate doses (e.g., curare as muscle relaxant).

Important Medicinal Plants

• Quinine (Cinchona calisaya): Anti-malarial agent from South American trees, also used for heart disease. Its chemical is used in tonic water.
• Ephedrine (Ephedra major, E. sinica): Amphetamine alkaloid from shrubs. Used in Chinese medicine for asthma, blood pressure, and coma treatments, and various over-the-counter remedies.
• Indian snakeroot (Rauwolfia serpentina): Reserpine (alkaloid) usage for mental illness, snakebites, blood pressure, schizophrenia, and hypertension.
• Foxglove (Digitalis purpurea): Cardiac glycosides (digoxin, digitoxin) for heart conditions.
• Madagascar periwinkle (Catharanthus roseus): Alkaloids for leukemia and Hodgkin's disease. Other plants offer anti-cancer properties.
• Yams (Dioscorea species): Diosgenin (saponin) for hormonal contraceptives, fertility drugs, hydrocortisone.
• Ginseng (Panax ginseng): Long-used in Chinese medicine, possible benefits include improved fitness and stress resistance, but more studies are needed.
• Coca (Erythroxylum coca): Mild stimulant historically chewed by the Inca. Cocaine (potent central nervous system stimulant, local anesthetic) is derived from it.
• Senna (Senna angustifolia): Laxative; cascara bark also used as a laxative.
• Opium Poppy (Papaver somniferum): Source of morphine, codeine, oxycodone, and heroin (pain relievers).
• Tropane Alkaloids (Solanaceae Family): Treat asthma, Parkinson's, and other conditions. Belladonna, henbane are examples.

Explore the rich history and biochemistry of medicinal plants used for over 5,000 years. This quiz delves into how early societies utilized plants for healing, the emergence of pharmacopoeias, and the significance of plant-derived medicines in contemporary healthcare. Discover fascinating examples and the economic impact of the global trade in medicinal plants.