Artocarpus lakoocha heartwood extract as a novel cosmetic ingredient: evaluation of the in vitro anti-tyrosinase and in vivo skin whitening activities

The heartwood extract of Artocarpus lakoocha Roxb. was evaluated for the in vitro tyrosinase inhibitory activity and the in vivo melanin-reducing efficacy in human volunteers. The IC(50) of the extract and oxyresveratrol, its major active ingredient, against mushroom tyrosinase was determined to be 0.76 and 0.83 mug mL(-1), respectively. The extract dissolved in propylene glycol was subsequently tested in female volunteers using a parallel clinical trial with self-control (n = 20 per group). The first group received the 0.25% w/v A. lakoocha solution as the test solution, whereas the second and the third group, respectively, received 0.25% licorice extract and 3% kojic acid as the reference solutions in the same solvent. The subjects in each group twice daily applied the test (or reference) solution in one of her upper arm, whereas the remaining arm was treated with only propylene glycol (self-control) for 12 weeks. The melanin content of each application site was measured using Mexameter every week and calculated as % reduction in melanin content relative to the initial melanin value (% whitening). The value of % whitening was then compared between the product-treated and the propylene glycol-treated arms within the same subject using paired t-test (alpha = 0.05). The A. lakoocha extract was the most effective agent, giving the shortest onset of significant whitening effect after only 4 weeks of application (P < 0.05), followed by 3% kojic acid (6 weeks) and 0.25% licorice extract (10 weeks). The effect also increased with time with maximum whitening observed at week 12 for A. lakoocha extract. When the extract was formulated as an oil-in-water emulsion, its whitening efficacy was further enhanced. Daily application of 0.1% w/w A. lakoocha lotion to the upper arms (n = 25) and cheeks (n = 15) of volunteers produced significant whitening over the lotion base after 2 and 3 weeks, respectively (P < 0.05). Thus, the preliminary study suggested that the heartwood extract of A. lakoocha may have a promising potential for use as an effective and economical skin-whitening agent.