In vitro Screening of Subtropical Plants Cultivated in Jeju Island for Cosmetic Ingredients

To identify novel cosmetic ingredients from subtropical plants, we screened 21 parts of 12 plant species collected from the Agricultural Research Institute for Climate located in Jeju Island, the southernmost island of the Korean Peninsula. Subtropical plants were investigated for their total polyphenolic content by using the Folin-Ciocalteu reagent with gallic acid as the standard as well as 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging activities. In both the DPPH and the ABTS assays, three plants, Syzygium samarangense, Acca sellowiana (leaves and branches), and Olea europaea (branches) showed significantly greater scavenging activity [half-maximal inhibitory concentration (IC50) < 50 mu g/mL] than the other plants did. The leaves and branches of S. samarangense also had the highest total phenolic content (153.7 and 160.6 mg gallic acid equivalent [GAE]/g DW, respectively). However, the subtropical plants in this study showed lower elastase and tyrosinase inhibition activities than the positive controls oleanolic acid and arbutin (95.0 and 86.5 mu g/mL, respectively) did. Furthermore, we sought to investigate the anti-inflammatory effects of these subtropical plants for potential use in topical applications to treat skin inflammation. Therefore, they were screened for inhibitory effects on the proinflammatory mediator, nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. Our results revealed that S. samarangense leaves potently inhibited the LPS-stimulated NO production concentration-dependently with an IC50 of 154.3 mu g/mL. These results suggest that these subtropical plants possess several biological activities that may be potent inhibitors of the skin aging and inflammatory processes. Further investigations will focus on cell-based in vitro assays and chemically identifying the major active components mediating the anti-aging and anti-inflammation.