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Jeju Island is the largest island located in the southernmost part of Korea. This island has diversity of a plant community and about 1,800 plant species exist around Halla mountain. We are searching plants to find natural products which are applicable as ingredients of cosmetic preparations.Sasa quelpaertensis Nakai (Korean name, Jejujoritdae), belonging to a family Gramineae, is an edible bamboo grass endemic to Jeju Island. S. quelpaertensis is one of the most abundant plant species among the plant varieties in the area of Halla Mountain. Its dried leaves are being used as a tea for the treatment of diabetes and gastritis in the local community. Our phytochemical studies on the leaves of this plant resulted in the isolation of 15 constituents including three new compounds. Among the isolates, anti-tyrosinase activities were identified in derivatives. In addition, a new phenylpropanoid isolate was identified to have anti-inflammation activities. It inhibits nitric oxide (NO) and prostaglandin E2 (PG E2) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. ESQ10 attenuated LPS-induced synthesis of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), in parallel, and inhibited LPS-induced interleukin-6 (IL-6) production, as determined by an enzyme-linked immunosorbent assay(ELISA), in the macrophages. Distylium racemosum Sieb. Et Zucc (Korean name: Joroknamu) belongs to a Hamamelidaceae family. This evergreen tree is distributed over the mountain area in Jeju. Twenty compounds were isolated from the ethanol extract of Distylium racemosum branches. The isolated compounds were identified as dibenzofurans, abscisic acid, 6’O-galloylsalidroside, catechin derivatives, gallic acid derivatives, tyrosol, flavonoids, lupeol, and 1,2,3,6-tetragalloylglucose. Among these isolates, four dibenzofurans were new compounds. Inhibitory activities on tyrosinase, elastase, and free radicals evaluated for the isolated compounds. M. fauriei (Leguminosae) is a large deciduous tree, endemic to Halla Mountain, Jeju Island. The EtOH extract of this plant was selected for bioactivity-guided fractionation due to its strong inhibition activities on mushroom tyrosinase. Bioassay-guided investigation of the stems of Maackia fauriei led to the isolation of seven flavonoid constituents, such as formononetin, genistein, daidzein, texasin, tectorigenin, odoratin, and mirkoin. Tyrosinase inhibition activities were carried out for the isolated compounds. Among these, mirkoin was identified as a potent tyrosinase inhibitor. It inhibited mushroom tyrosinase with an IC50 value of 0.005 mM, which is ten times more active than kojic acid (IC50 = 0.045 mM). The inhibition kinetics, analyzed by Lineweaver-Burk plots, indicated mirkoin to be a competitive inhibitor of tyrosinase when L-tyrosine was used as a substrate.