Inhibition of Aromatase Activity by Green Tea Extract Catechins and Their Endocrinological Effects of Oral Administration in Rats

Food Chem Toxicol. 2002 Jul;40(7):925-33. doi: 10.1016/s0278-6915(02)00066-2.


We orally administered polyphenone-60 (P-60), green tea extract catechins, in the diet (0, 1.25 and 5%) to male rats for 2, 4 and 8 weeks initiated at 5 weeks old. It was found that a 5% dose to male rats for 2-8 weeks induced goiters and decreased weights of the body, testis and prostate gland. Endocrinologically, elevating plasma thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels and decreasing tri-iodothyronine (T(3)) and thyroxine (T(4)) levels were induced by this treatment. We also found that P-60 as a whole and some of its constituents exhibited inhibitory effects on human placental aromatase activity by in vitro assay. The concentration of P-60 that required producing 50% inhibition of the aromatase activity (IC(50) value) was 28 microg/ml. The IC(50) values of (-)-catechin gallate (Cg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-gallocatechin gallate (GCg) were 5.5 x 10(-6), 1.0 x 10(-4), 6.0 x 10(-5) and 1.5 x 10(-5) M, respectively. (-)- Epicatechin gallate (ECg) at 1.0 x 10(-4) M produced 20% inhibition. (-)-Epicatechin (EC) and (+)-catechin (CT) exhibited no effects on aromatase activity. The endocrinological changes observed in vivo were in conformity with antithyroid effects and aromatase inhibition effects of P-60 and its constituents.

MeSH terms

  • Administration, Oral
  • Animals
  • Aromatase Inhibitors*
  • Follicle Stimulating Hormone / blood
  • Luteinizing Hormone / blood
  • Male
  • Organ Size / drug effects
  • Plant Extracts / administration & dosage
  • Plant Extracts / pharmacology*
  • Rats
  • Rats, Inbred F344
  • Tea / chemistry*
  • Testosterone / blood
  • Thyroid Hormones / blood
  • Thyrotropin / blood


  • Aromatase Inhibitors
  • Plant Extracts
  • Tea
  • Thyroid Hormones
  • Testosterone
  • Luteinizing Hormone
  • Follicle Stimulating Hormone
  • Thyrotropin