Green tea | Pharmacology Mentor

Generic Name

Catechins

Catechins (especially epigallocatechin‑3‑gallate, EGCG) are the primary bioactive compounds.
Antioxidant activity: scavenges reactive oxygen species (ROS) and up‑regulates endogenous antioxidant enzymes (e.g., superoxide dismutase).
Inhibition of pro‑inflammatory signaling: EGCG blocks NF‑κB and MAPK pathways, reducing cytokine production.
Modulation of lipid metabolism: activates AMP‑activated protein kinase (AMPK), enhancing fatty acid oxidation and decreasing lipogenesis.
Cardiovascular protection: improves endothelial function by increasing nitric‑oxide bioavailability and reducing platelet aggregation.
Neuroprotective effects: inhibits β‑amyloid aggregation and reduces oxidative neuronal damage.

Parameter	Typical Values	Notes
Absorption	20–80 % of catechins from the gut; peak plasma 1–3 h post‑drink	Food reduces absorption by ~30 %; simultaneous intake of iron or high‑fat meals further impedes catechin uptake.
Distribution	Wide tissue distribution; crosses the blood‑brain barrier	Conjugation with glucuronic acid and sulfates enhances solubility.
Metabolism	Phase‑II conjugation (glucuronidation, sulfation, methylation) predominates; minimal CYP450 involvement	Minor CYP1A2 inhibition can alter caffeine metabolism.
Elimination	Renal excretion (~60 %) and biliary excretion (~30 %)	Half‑life of EGCG: 2–5 h; caffeine lasts ~5 h.

Cardiovascular risk reduction (hypertension, dyslipidemia).
Weight management: modest lipid oxidation and appetite suppression.
Neurodegenerative disease prevention (early stages of Alzheimer’s and Parkinson’s).
Metabolic syndrome: improves fasting glucose and insulin sensitivity.
Helicobacter pylori adjunct: potentiates eradication regimens.

Pregnancy / lactation: high caffeine and catechin exposure not recommended.
G6PD deficiency: risk of hemolysis with excessive catechin intake.
Active liver disease: risk of hepatotoxicity at high doses (>400 mg/day EGCG).
Bleeding disorders: catechin‑induced platelet inhibition may worsen bleeding risk.
Caffeine hypersensitivity: avoid high‑caffeine preparations.

Standard dosage: 1‑2 g dry tea leaves (≈2–3 cups) per day, 2–3 times daily.
High‑dose supplements: 300–800 mg EGCG per day should be split into 2–3 doses.
Preparation: steep at 90–95 °C for 2–3 min; avoid prolonged decoction (>5 min) to limit excessive catechin release.
Timing: best taken between meals to mitigate GI irritation; can be taken 30 min before exercise to enhance fat oxidation.

Common: mild gastrointestinal upset, nausea, dyspepsia, belching.
Caffeine‑related: tremor, palpitations, insomnia, anxiety.
Serious: hepatotoxicity (raised ALT/AST), hemolytic anemia (G6PD), severe GI bleeding, exacerbation of migraine in susceptible individuals.

Liver enzymes (ALT, AST) annually for high‑dose users.
CBC if G6PD status unknown or symptoms of hemolysis develop.
Blood pressure and lipid profile at baseline and 6–12 months for cardioprotective use.
Caffeine level avoided; observe for tolerance or withdrawal.

Bioavailability tricks: consume green tea with moderate fat or calcium to protect endangered taste buds, but avoid strong iron or calcium supplements until 30 min post‑tea.
Surrogate marker: urinary catechin levels can gauge adherence in research settings.
Allergies & HPI: a small subset of patients reports anaphylactoid reactions—rare but consider in patients with severe allergy history.
Drug interactions: beware of MAO‑inhibitor interference with tea‑derived phenolics; advise a 4‑hour gap.
Dental health: green tea contains fluoride and polyphenols that can reduce plaque formation; patients can benefit from routine dental check‑ups.
Fun fact: the synergistic effect of green tea catechins and resveratrol (found in grapes) has been documented in a few in vitro studies—mindful of polypharmacy.

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