Ryeo Kyeong Ko

Compounds with Tyrosinase Inhibition, Elastase Inhibition and DPPH Radical Scavenging Activities from the Branches of Distylium racemosum Sieb. et Zucc

Twenty compounds were isolated from the ethanol extract of Distylium racemosum branches and their inhibitory activities on tyrosinase, elastase and free radicals evaluated. The isolated compounds were identified as dibenzofurans (1–4), abscisic acid (5), 6′‐O‐galloylsalidroside (6), catechin derivatives (7–11), gallic acid derivatives (12–14), tyrosol (15), flavonoids (16–18), lupeol (19) and 1,2,3,6‐tetragalloylglucose (20). For study of tyrosinase inhibition activities, when compared with arbutin (IC50 48.8 μg/mL), four compounds (8, 11, 13, 17) showed higher activities, with IC50 values of 4.8, 30.2, 40.5 and 37.7 μg/mL, respectively. For the elastase inhibition test, dibenzofuran 1 showed greater activity than the positive control, oleanolic acid (IC50 9.7 μg/mL), with an IC50 of 7.7 μg/mL. In the studies on DPPH radical scavenging activities, five compounds (11, 12, 13, 14, 15) showed higher activities than ascorbic acid (IC50 5.0 μg/mL), with IC50 values of 4.6, 3.9, 2.9, 3.8 and 4.7 μg/mL, respectively. Copyright

Diphlorethohydroxycarmalol, isolated from the brown algae Ishige okamurae, protects against radiation-induced cell damage in mice

The aim of this study was to evaluate the radioprotective effects of diphlorethohydroxycarmalol (DPHC), isolated from the brown algae Ishige okamurae, in mice subjected to gamma irradiation. DPHC significantly decreased the level of radiation-induced intracellular reactive oxygen species in cultured Chinese hamster lung fibroblast (V79-4) cells (p < 0.05), enhanced cell viability that decreased after exposure to γ-rays, and reduced radiation-induced apoptosis in the V79-4 cells. Pretreatment with DPHC (100 mg/kg) in mice prior to irradiation significantly protected the intestinal crypt cells in the jejunum (p < 0.01) and maintained villi height (p < 0.01), compared with those of the vehicle-treated irradiated group. Mice pretreated with DPHC also exhibited dose-dependent increases in the bone marrow cell viability. The dose-reduction factor for gamma irradiation in the DPHC-pretreated mice was 2.05 at 3.5 days after irradiation. These results suggest that DHPC plays a role in protecting cells from irradiation-induced apoptosis, through the scavenging of reactive oxygen species in vitro, and that DPHC significantly protected intestinal progenitor cells and bone marrows cells that were decreased by gamma irradiation in vivo.

Tyrosinase inhibitory constituents from the stems of Maackia fauriei

Bioassay‐guided investigation of the stems of Maackia fauriei led to the isolation of seven flavonoid constituents, formononetin (1), genistein (2), daidzein (3), texasin (4), tectorigenin (5), odoratin (6) and mirkoin (7). Their structures were elucidated on the basis of spectral studies as well as by comparison with literature data. Tyrosinase inhibition activities were carried out on the isolated compounds. Among these, mirkoin (7) 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, analysed by Lineweaver‐Burk plots, indicated mirkoin (7) to be a competitive inhibitor of tyrosinase when l‐tyrosinase was used as a substrate. The results suggest that hydroxyl groups at C‐4′ in the B ring of flavonoids play an important role in the tyrosinase inhibition activities. Interestingly, compounds 4–7 were isolated for the first time from this plant. Copyright