Toxicological studies on procyanidin B-2 for external application as a hair growing agent

Procyanidin B-2 [epicatechin-(4beta --> 8)-epicatechin] is one of condensed tannin that exists widely in plants. We have reported previously that procyanidin B-2 possesses hair epithelial cell growth-promoting activity and stimulates anagen induction in hair cycle progression. To evaluate the safety of topical procyanidin B-2 as a hair growing agent, we examined the mutagenicity, acute subcutaneous injection, primary irritation, skin sensitization, and eye irritation of this compound. Mutagenicity tests using bacteria showed procyanidin B-2 to be non-mutagenic. Chromosomal aberration tests using CHL cells indicated that procyanidin B-2 caused polyploidy but no structural aberrations. In micronucleus tests for mutagenicity using mice, procyanidin B-2 was negative. Acute subcutaneous injection study using rats revealed no symptoms of significant injury. The lethal dose of procyanidin B-2 is greater than 2000 mg/kg (subcutaneous injection). Primary irritation tests using rabbits indicated that procyanidin B-2 containing preparation shows no primary irritation. In the guinea pig maximization test, there was no evidence of sensitization to procyanidin B-2. In primary ocular irritation tests using rabbits, procyanidin B-2 containing preparation and vehicle showed slight irritation of conjunctivae which is assumed to be caused by ethanol. It is suggested that topical procyanidin B-2 is safe and acceptable from the series of toxicological tests.