• 동의생리병리학회지
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• 제23권3호
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• pp.574-580
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• 2009

Melanogenesis is induced mainly by ultraviolet radiation of sunlight and ${\alpha}$-Melanocyte stimulation hormone (${\alpha}$-MSH) which binds to a specific G protein coupled receptor. ${\alpha}$-MSH and cAMP-elevating agents are known to melanin syntheisis and dendrite outgrowth. The purpose of this study was to investigate the mechanism of melanogenesis inhibition in B16/F10 cells by ethanol extract of Artemisiae Capillaris Herba. In the present study, ${\alpha}$-MSH led to a stimulation of melanin synthesis that appeared to result from an increased tyrosinase activity and melanin content. However, the ethanol extract of Artemisiae Capillaris Herba inhibited the ${\alpha}$-MSH-induced tyrosinase activity and melanin content. In control conditions, B16/F10 cells displayed a fibroblastic appearance while ${\alpha}$-MSH treatment promoted the emergence of small and numerous dendrites from the plasma membrane. The ethanol extract of Artemisiae Capillaris Herba abolished the ${\alpha}$-MSH-induced dendricity. Regarding protein levels of the melanogenic enzymes, the amounts of tyrosinase were increased after incubation with ${\alpha}$-MSH. The treatment of Artemisiae Capillaris Herba ethanol extract decreased the ${\alpha}$-MSH expression levels of tyrosinase. Based on these findings, it is likely that the ethanol extract of Artemisiae Capillaris Herba exerts its depigmenting effects in B16/F10 cells through the suppression of tyrosinase expression, which are key enzymes for melanogenesis.

• Archives of Pharmacal Research
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• 제28권7호
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• pp.784-790
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• 2005

In this study, we evaluate the effects of (-)-epigallocatechin-3-gallate (EGCG) on ultraviolet B(UVB)-irradiated living skin equivalents (LSEs). Histologically, UVB irradiation induced thinning of the LSE epidermis, whereas EGCG treatment led to thickening of the epidermis. Moreover, EGCG treatment protected LSEs against damage and breakdown caused by UVB exposure. Immunohistochemically, UVB-exposed LSEs expressed p53, Fas, and 8-hydroxy-deoxyguanosine (8-OHdG), all of which are associated with apoptosis. However, EGCG treatment reduced the levels of UVB-induced apoptotic markers in the LSEs. In order to determine the signaling pathways induced by UVB, Western blot analysis was performed for both c-Jun $NH_2$-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), which are associated with UVB-induced oxidative stress. UVB activated JNK in the epidermis and dermis of the LSEs, and EGCG treatment reduced the UVB-induced phosphorylation of JNK. In addition, p38 MAPK was also found to have increased in the UVB-exposed LSEs. Also, EGCG reduced levels of the phosphorylation of UVB-induced p38 MAPK. In conclusion, pretreatment with EGCG protects against UVB irradiation via the suppression of JNK and p38 MAPK activation. Our results suggest that EGCG may be useful in the prevention of UVB-induced human skin damage, and LSEs may constitute a potential substitute for animal and human studies.

• 동의생리병리학회지
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• 제21권6호
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• pp.1456-1461
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• 2007

Melanogenesis is induced mainly by ultraviolet radiation of sunlight and ${\alpha}-melanocyte$-stimulating hormone (${\alpha}-MSH$) which binds to a specific G protein coupled receptor. The purpose of this study was to investigate the mechanism of melanogenesis inhibition in B16/F10 cells by methanol extract of Rubus coreanus Miquel (RCM). In the present study, ${\alpha}-MSH$ and forskolin led to a stimulation of melanin synthesis that appeared to result from an increased tyrosinase activity and melanin content. However, RCM inhibited the ${\alpha}-MSH$- and forskolin-induced melanin synthesis. In addition, RCM abolished the ${\alpha}-MSH$- and forskolin-induced cytoplasmic dendricity. Regarding protein levels of the melanogenic enzymes, the amounts of tyrosinase and tyrosinase-related protein 1 (TRP-1) were increased after incubation with α-MSH and forskolin. The treatment of RCM decreased the ${\alpha}-MSH$- and forskolin-induced expression levels of tyrosinase and TRP-1. Based on these findings, it is likely that RCM exerts its depigmenting effects in B16/F10 cells through the suppression of tyrosinase and TRP-1 expression, which are key enzymes for melanogenesis.

• 한국재료학회지
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• 제18권2호
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• pp.92-97
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• 2008

In spray pyrolysis, the effects of the preparation temperature, flow rate of the carrier gas and concentration of the spray solution on characteristics such as the morphology, size, and emission intensity of $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders under long-wavelength ultraviolet light were investigated. The phosphor powders obtained post-treatment had a range of micron sizes with regular morphologies. However, the composition, crystal structure and photoluminescence intensity of the phosphor powders were affected by the preparation conditions of the precursor powders. The $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders prepared at temperatures that were lower and higher than $700^{\circ}C$ had low photoluminescence intensities due to deficiencies related to the of Cl component. The phosphor powders with the deficient Cl component had impurity peaks of $Ca_2SiO_4$. The optimum flow rates of the carrier gas in the preparation of the $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders with high photoluminescence intensities and regular morphologies were between 40 and 60 l/minute. Phosphor powders prepared from a spray solution above 0.5 M had regular morphologies and high photoluminescence intensities.

• 한국식품영양과학회지
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• 제41권12호
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• pp.1798-1804
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• 2012

국내산 복숭아에의 저장성 증진을 위하여 0~10.0 $kJ/m^2$의 선량으로 UV-C를 처리하고 저장 중 부패율, 이화학적 변화 및 기호도의 변화를 측정하였다. 대조군 및 2.5 $kJ/m^2$ UV-C 처리군의 경우 부패율은 저장 4일까지는 부패된 것이 하나도 없었으나 저장 6일 이후부터는 부패된 복숭아를 보이기 시작하였으며 저장 10일에는 각각 29.17% 및 25.0%의 부패율을 나타내었다. 그러나 5.0, 7.5 및 10 $kJ/m^2$의 UV-C 처리군에서는 저장 10일에 각각 41.67, 50.00 및 58.33%로 조사선량이 높을수록 더 많은 부패율을 나타내었다. 무게변화의 경우 대조군과 2.5 $kJ/m^2$ UV-C 처리군은 저장 10일동안 변화폭이 가장 적었으나 5.0 $kJ/m^2$ 이상의 처리군에서는 이들보다 많은 변화를 보였다. 복숭아의 pH 변화에서는 UV-C 처리에 의한 차이를 보이지 않았으며 저장기간 중 pH가 증가하였으나 모든 실험군에서 유의적인 차이가 없는 것으로 나타났다. 경도에서는 UV-C 처리 직후에는 모든 실험군에서 차이가 없었으나 저장 6일까지는 2.5 $kJ/m^2$ 처리군이 대체적으로 대조군과 비슷하거나 약간 높은 경도를 보였으며 저장 8일 이후에는 대조군보다 감소하였다. 그러나 5.0 $kJ/m^2$ 이상의 처리군에서는 저장 4일 이후부터는 빠르게 경도가 감소하는 것으로 나타났다. 명도 변화에서는 UV-C 처리 및 저장 중 모든 실험군에서 큰 차이를 보이지는 않았으며 적색도는 처리 직후에는 차이가 없었으며 대체적으로 저장 중 대조군과 마찬가지로 증가하는 경향이었다. 황색도는 UV-C 처리에 의하여 다소 황색도가 낮아졌으며 저장 중에는 모든 실험군이 약간 증가하였으나 유의적인 차이를 보이지는 않았다. 맛, 향, 색, 조직감 및 종합적 기호도의 변화에서는 UV-C 처리에 의한 변화는 없는 것으로 나타났다. 그러나 저장 중 모든 실험군에서 2일 혹은 4일차에 가장 높은 기호도를 보였으며 그 후부터는 기호도값이 감소하였다. 전반적으로 대조군과 2.5 $kJ/m^2$ UV-C 처리군이 가장 기호도가 높은 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.23-23
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• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.327-327
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• 2009

ZnO with a large band gap (~3.37 eV) and exciton binding energy (~60 meV), is suitable for optoelectronic applications such as ultraviolet (UV) light emitting diodes (LEDs) and detectors. However, the ZnO-based p-n homojunction is not readily available because it is difficult to fabricate reproducible p-type ZnO with high hall concentration and mobility. In order to solve this problem, there have been numerous attempts to develop p-n heterojunction LEDs with ZnO as the n-type layer. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducible availability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices. In particular, a number of ZnO films show UV band-edge emission with visible deep-level emission, which is originated from point defects such as oxygen vacancy, oxygen interstitial, zinc interstitial[1]. Thus, defect-related peak positions can be controlled by variation of growth or annealing conditions. In this work, the undoped ZnO film was grown on the p-GaN:Mg film using RF magnetron sputtering method. The undoped ZnO/p-GaN:Mg heterojunctions were annealed in a horizontal tube furnace. The annealing process was performed at $800^{\circ}C$ during 30 to 90 min in air ambient to observe the variation of the defect states in the ZnO film. Photoluminescence measurements were performed in order to confirm the deep-level position of the ZnO film. As a result, the deep-level emission showed orange-red color in the as-deposited film, while the defect-related peak positions of annealed films were shifted to greenish side as increasing annealing time. Furthermore, the electrical resistivity of the ZnO film was decreased after annealing process. The I-V characteristic of the LEDs showed nonlinear and rectifying behavior. The room-temperature electroluminescence (EL) was observed under forward bias. The EL showed a weak white and strong yellowish emission colors (~575 nm) in the undoped ZnO/p-GaN:Mg heterojunctions before and after annealing process, respectively.

• Korean Chemical Engineering Research
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• 제44권6호
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• pp.609-613
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• 2006

분무열분해법에 의해 장파장 UV 여기원 하에서 높은 발광세기를 가지는 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체를 제조하였다. 분무열분해공정 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체의 발광특성, 분말 형태 및 결정성에 대해 조사하였다. 분무열분해 공정에 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 모체를 구성하는 바륨과 스트론튬의 비에 따라 청녹색에서 황색에 이르기까지 다양한 파장대의 색을 구현할 수 있었다. x = 0인 $Ba_2SiO_4:Eu^{2+}$ 형광체의 경우 발광 중심파장이 500 nm였으며, x = 2인 $Sr_2SiO_4:Eu^{2+}$ 형광체의 경우 발광중심 파장이 554 nm였다. 분무열분해 공정에 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 구형의 형상을 띄지만 중공성의 입자 특성을 가졌다. 반면에 후열처리 과정을 거친 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 큰 입자 크기와 불규칙한 형태를 가졌다. $Ba_{1.488}Sr_{0.5}SiO_4:Eu_{0.012}{^{2+}}$ 형광체가 환원분위기 하에서 후열처리 온도 $1,200^{\circ}C$에서 3시간 동안 후열처리 과정을 거쳤을 때 최적의 발광 세기를 가졌다.

• 한국재료학회지
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• 제15권6호
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• pp.408-412
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• 2005

[ $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ ] phosphor particles with high photoluminescence intensity under long wavelength ultraviolet were prepared by spray pyrolysis. We investigated the effect of $NH_4F$ flux added into starting solution on the morphology and photoluminescence intensity of $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ phosphor prepared by spray pyrolysis. $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ phosphor particles prepared from starting solution containing $NH_4F$ flux had the maximum photoluminescence intensity at the post-treatment temperature of $1200^{\circ}C$ and the maximum photoluminescence intensity of $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ phosphor particles prepared from the starting solution containing $NH_4F$ flux was $137\%$ of that of the phosphor particles prepared from the starting solution without flux material. $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ phosphor particles prepared from starting solution containing $NH_4F$ flux had larger size and more aggregated morphology than those prepared from starting solution without flux material. The photoluminescence intensity of $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ phosphor particles prepared from starting solution containing $NH_4F$ flux above $3wt.\%$ had high photoluminescence intensities. The addition amount of $NH_4F$ flux showing the maximum photoluminescence intensity was $12wt.\%$. The optimum amount of $NH_4F$ flux was $5wt.\%$ when we considered the morphological and photoluminescence characteristics of $Ba_{1.5}Sr_{0.5}SiO_4:Eu$ ohosphor particles prepared by spray pyrolysis.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 춘계학술대회
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• pp.21-22
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• 2019

Melanin is a mixture of pigmented biopolymers synthesized by epidermal melanocytes that determine the skin, eye, and hair colors. Melanocytes produce two different kinds of melanin, eumelanin (dark brown/black insoluble pigments found in dark skin and dark hair and pheomelanin (lighter red/yellow). The biological role of melanin is to prevent skin damage by ultraviolet (UV) radiation. However, the overproduction or deficiency of melanin synthesis could lead to serious dermatological problems, which include melasma, melanoderma, lentigo, and vitiligo. Therefore, regulating melanin production is important to prevent the pigmentation disorders. Myanmar has a rich in natural resources. However, the chemical constituents of these natural resources in Myanmar have not been fully investigated. In the effort to search for compounds with anti-melanin deposition activity from Myanmar natural resources, five plants were collected in Myanmar. Extracts of these collected five plants were tested for anti-melanin deposition activity against a mouse melanoma cell line (B16-F10) induced with ${\alpha}$-melanocyte-stimulating hormone (${\alpha}$-MSH) and 3-isobutyl-1-methylxanthine (IBMX), and their anti-melanin deposition activities were compared with the positive control, arbutin. Among the tested extracts, the CHCl3 extracts of the Premna serratifolia (syn: P. integrifolia) wood showed anti-melanin deposition activities with IC50 values of $81.3{\mu}g/mL$. Hence, this study aims to identify secondary metabolites with anti-melanin deposition activity from P. serratifolia wood of Myanmar. P. serratifolia belongs to the Verbenaceae family and is widely distributed in near western sea coast from South Asia to South East Asia, which include India, Malaysia, Vietnam, Cambodia, and Sri Lanka. People in Tanintharyi region located in the southern part of Myanmar utilize the P. serratifolia, Sperethusa crenulata, Naringi crenulata, and Limonia acidissima as Thanaka, traditional cosmetics in Myanmar. Thanaka is applied in the form of paste onto skins to make it smooth and clear, as well as to prevent wrinkles, skin aging, excessive facial oil, pimples, blackheads, and whiteheads. However, the chemical constituents responsible for their cosmetic properties are yet to be identified. Moreover, the chemical constituents of P. serratifolia was almost uncharacterized. Investigation of the P. serratifolia chemical constituents is thus an attractive endeavor to discover new anti-melanin deposition active compounds. The investigation of the chemical constituents of the active CHCl3 extract of P. serratifolia led to isolation of four new lignoids, premnan A (1), premnan B (2), taungtangyiol C (3), and 7,9-dihydroxydolichanthin B (4), together with premnan C (5) (assumed to be an artifact), one natural newlignoid,(3R,4S)-4-(1,3-benzodioxol-5-ylcarbonyl)-3-[(R)-1-(1,3-benzo dioxol-5-yl)-1-hydroxy methyl]tetrahydro-2-furanone (6), and five known compounds (7-11)1,2). The structures of all isolated compounds were determined on the basis of their spectroscopic data and by comparison with the reported literatures. The absolute configurations of 1-3 and 5 were also determined by optical rotation and circular dichroism (CD) data analyses1). The anti-melanin deposition activities of all the isolated compounds were evaluated against B16-F10 cell line. 7,9-Dihydroxydolichanthin B (4) and ($2{\alpha},3{\alpha}$)-olean-12-en-28-oic acid (11) showed strong anti-melanin deposition activities with IC50 values of 18.4 and $11.2{\mu}M$, respectively, without cytotoxicity2). On the other hand, compounds 1-3, 5, and 7 showed melanogenesis enhancing activities1). To better understand their anti-melanin deposition mechanism, the effects of 4 and 11 on tyrosinase activities were investigated. The assay indicated that compounds 4 and 11 did not inhibit tyrosinase. Furthermore, we also examined the mRNA expression of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). Compounds 4 and 11 down-regulated the expression of Tyr and Mitf mRNAs, respectively. Although the P. serratifolia wood has been used as traditional cosmetics in Myanmar for centuries, there are no scientific evidences to support its effectiveness as cosmetics. Investigation of the anti-melanin deposition activity of the chemical constituents of P. serratifolia thus provided insight into the effectiveness of the P. serratifolia wood as a cosmetic agent.