| Ultraviolet (UV) radiation on the surface of the earth is certainly increasing as a result of the depletion of stratospheric ozone. High-intensity or accumulated UV radiation provokes many hyperpigmentation disorders, which are of particular concern to women as well as men. In recent years, the study of traditional herbal medicines for skin-protecting and skin-lighting has become a hot spot in the cosmetics field, due to various safety concerns and interesting largely unexplored sources. In this dissertation, the main objective was to investigate the potential usage of clove oil, citronella oil and Litsea cubeba oil as natural sources of tyrosinase inhibitor, antioxidant, and protection protein against UV-TiO2-NO2-induced protein oxidation and tyrosine nitration injury. The main results are as follows:1. The clove oil, citronella oil and Litsea cubeba oil extracted by hydrodistillation, showed light yellow in color. The total of10compounds was identified by GC-MS in the clove oil, accounting for94.8%of the total oil. The main components were eugenol (76.8%), followed by eugenyl acetate (9.5%) and β-caryophyllene (6.0%). Essential oil from Cymbopogon goeringii leaves was also analyzed by GC-MS, resulted in the identification of17compounds representing93.5%of the oil. Citronellal (33.9%), geraniol (18.1%), and citronellol (11.1%) were the main compounds. GC-MS analyses of Litsea cubeba oil led to identification of19different compounds, accounting for92.4%of the total oil. The main components were citral representing57.4%of the total amount of oil extracted, follow by limonene (8.1%), linalool (5.2%), β-myrcene (4.7%), α-terpineol (3.9%), β-pinene(2.7%) and a-pinene(1.9%).2. Tyrosinase inhibitory assay was used to evaluate whether the three essential oils and their main components possessed potential inhibitory effect on tyrosinase. The results show that Litsea cubeba oil and citral exhibited inhibitory effect on monophenolase and diphenolase activity of tyrosinase. The inhibitory effect of Litsea cubeba oil and citral on diphenolase activity was stronger than monophenolase activity of tyrosinase. The inhibition pattern of mushroom tyrosinase by citral was determined by Lineweaver-Burk polt analysis. The results demonstrated that citral was a noncompetition tyrosinase inhibitor. Clove oil and eugenol exhibited some inhibitory effect on monophenolase activity of tyrosinase, but not show any inhibitory effect on diphenolase activity of tyrisinase. Citronella oil and their main components didn’t exhibited any inhibitory effect.3. In order to determine whether the three essential oils and their main components had antioxidant activity, ABTS cation radical scavenging assay, superoxide anion radical scavenging assay and lipid peroxidation assay were carried out. Clove oil exhibited prominent radical scavenging activities (IC50:58μg/mL for O2-and8.5μg/mL for ABTS+) and strong inhibitory effect on lipid peroxidation, whilst citronella oil showed weaker antioxidative activities (IC50:150μg/mL for O2-and500μg/mL for ABTS+) and lipid peroxidation inhibitory efficiency. Litsea cubeba oil exhibited the lowest anti-oxidative activities (IC50:17.75mg/mL for ABTS+’,10.2mg/mL for O2-).4. In order to investigate inhibitory effects of essential oils to UV-TiO2-NO2-induced protein oxidation and protein tyrosine nitration injury, bovine serum albumin (BSA) were used as model protein, inhibition were followed by SDS-PAGE and Western blotting methods. The results showed that clove oil, citronella oil and Litsea cubeba oil exhibited satisfactory protective effects and revealed dose-dependence in protecting BSA against UV-TiO2-NO2-induced protein oxidation and tyrosine nitration injury. |
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