A Potent Tyrosinase Inhibitor from Artocarpus Lakoocha Heartwood Extract: Comparative Evaluation of Its Melanin- Reducing Efficacy in Guinea Pigs and Humans

The heartwood extract of Artocarpus lakoocha Roxb., which contains a potent tyrosinase inhibitor oxyresveratrol, was evaluated for its melanin-reducing efficacy in both guinea pigs and human volunteers. After 4 week-daily application of the extract dissolved in propylene glycol to the back of guinea pigs, significant reduction in melanin content was detected, with the effect greater than 3% kojic acid and solvent propylene glycol (P < 0.05). The extract was subsequently tested in female volunteers (3 groups of 20 subjects) using a parallel clinical trial with self-control. The first group received the A. lakoocha solution in propylene glycol whereas the second and the third group respectively received 0.25% licorice extract and 3% kojic acid in the same solvent. The subject in each group twice daily applied the test solution on one arm whereas the remaining arm was applied with only propylene glycol (self-control) for 12 weeks. The A. lakoocha extract was found to be the most effective agent, giving the shortest onset of significant whitening after only 4 weeks of application (P < 0.05), followed by 3% kojic acid (8 weeks) and 0.25% licorice extract (10 weeks). The whitening effect also increased with time, with the highest extent observed with A. lakoocha at week 12. The in vitro antityrosinase activity of A. lakoocha extract decreased with time upon storage at room temperature but could be stabilized by a combination of several antioxidants. In conclusion, the heartwood extract of A. lakoocha appeared to have promising potential for use as an effective and economical skin-whitening agent.