In Vitro and i n Vivo Demonstration of the Beneficial Effects of a Caesalpinia sappan Seeds Extract on Human Skin: From ROS Scavenging to Dark Spot Bleaching

Abstract

Background: Caesalpinia sappan seeds have recently shown beneficial effects on human health because of its content in anti-inflammatory and antioxidant compounds. Reasoning that these compounds could also display beneficial effects on human skin, we investigate the antioxidant power of a Caesalpinia sappan seeds extract and its ability to protect skin against oxidative attacks. Additionally, as inflammation is often related to oxidative bursts, we evaluate the potency of our extract to act on inflammation. Finally, as our Caesalpinia sappan seeds extract is particularly rich in 4-methyl-catechol, a well-known divalent cation chelator, we test its ability to reduce tyrosinase activity which depends on the presence of copper ions, and by this way to produce any significant whitening effect on human skin. Materials and Methods : In the first part of our study, intrinsic potential of our Caesalpinia sappan seeds extract was evaluated by using a paramagnetic radical, i.e. the DiPhenl Pricryl Hydrazyl (DPPH), which emits specific colorations following its oxidation state. For the second time, we took advantage of our original model of enrichment of epidermis cell cultures in progenitor cells to show the ability of our extract to protect progenitor cells against UV irradiations. Subsequently, the potency of our Caesalpinia sappan seeds extract to inhibit Lysyl Oxidase (LOX) activity was evaluated in an in vitro model composed by a purified human enzyme. Concerning the putative whitening effect of our Caesalpinia sappan seeds extract, it was assessed in several steps: 1) measurement of its inhibitory effect on tyrosinase activity in an in vitro acellular model calling for a mushroom enzyme, 2) measurement of its inhibitory effect on melanogenesis in a model of human normal melanocytes, and at last 3) assessment of its whitening effect, and notably its bleaching effect on dark spots, in an in vivo model calling for human volunteers. Results: Our Caesalpinia sappan seeds extract strongly inhibited DPPH oxidation from 33.2 +/− 4.9% to 97.1 +/− 0.5% for Caesalpinia sappan seeds concentrations from 0.01 to 1% (v/v), respectively. As a consequence, Caesalpinia sappan seeds extract was able to efficiently protect cutaneous progenitor cells against UVB radiations from 51.1 +/− 1.7% to 86.2 +/− 3.8% of protection for Caesalpinia sappan seeds concentrations from 0.00015 to 0.0015% (v/v), respectively. LOX activity was significantly reduced by the Caesalpinia sappan seeds extract from 69.4 +/− 3.6 to 91.1 +/− 1.5% for concentrations from 0.01 to 1% (v/v), respectively. The activity of another tested copper-dependent enzyme, i.e. tyrosinase, was for its part, virtually totally inhibited by our Caesalpinia sappan seeds extract for concentrations as low as 0.5% (v:v). Subsequently, human melanogenesis was significantly inhibited by the tested extract: from 34.4 +/− 5.8% to 93.7 +/− 5.8% of inhibition for Caesalpinia sappan seeds extract concentrations comprised between 0.001 and 0.005% (v/v). Finally, the surface of dark spots on human volunteer’s skin was significantly reduced by 22.2% after 28 days of use of a formulation containing 1% of our Caesalpinia sappan seeds extract. Conclusion: Caesalpinia sappan seeds not only display beneficial effects on human health through their actions on digestive tract but also can protect human skin against oxidative attacks and, thanks to their copper chelating activity, efficiently act against inflammatory bursts and significantly reduce skin dark spots coloration intensity.