| Summary: | 碩士 === 嘉南藥理科技大學 === 生物科技系暨研究所 === 96 === Tamarillo, Cyphomandra betacea Sendt. , is a subtropical fruit containing anthocyanins and carotenoids. To better understand whether tamarillo fruit could prevent oxidative stress and be used as a whitening agent in cosmetics, we analyzed the total phenol contents and investigated the biochemical properties of the ethanol extract and its partitioned fractions on free radical scavenging, anti-LDL oxidation and anti-tyrosinase activities. There is considerable evidence indicated that atherogenesis is initiated and promoted by oxidation of low-density lipoprotein (LDL). Dietary antioxidants might reduce the risk of atherosclerosis by scavenging free radical and reduction of LDL oxidation. Tyrosinase (EC 1.14.18.1) is a key enzyme involved in the synthesis of melanin, which plays a major role in human skin pigmentation. Compounds which inhibit tyrosinase activity could be effective as depigmenting agents. The ethanol extract of tamarillo fruit contained a high content of phenolic compounds [ 28.8 ± 0.05 mg catechin equivalents (CE)/g dry weight ] and showed a strong DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity [ IC50 = 189.1 ± 1.3 μg/mL ]. Further solvent partition of the ethanol extract yielded ethyl acetate (EA), n-butanol, and water layers. Among them, EA layer had the highest phenol content [ 61.1 ± 0.06 mg (CE)/g dry weight ], DPPH scavenging potential [ IC50 = 89.1 ± 4.2 μg/mL ] and TEAC [ 56.73 ± 4.5 mg/g ]. Tamarillo phenolics in EA layer also exhibited stronger or compatible inhibitory activity than DL-?tocopherol, at the same working concentration, Copper-induced LDL oxidation was suppressed by the tamarillo phenolics in EA layer more effectively or compatible to DL-??tocopherol, as measured by decreased formation of thiobarbituric acid-reactive substances assay（TBARS）, conjugated diene and electrophoretic mobility（REM）. Tyrosinase activity and enzyme kinetics was analyzed by Michaelis-Menten approach. The methanol fraction contained strong competitive inhibitors on mushroom tyrosinase with IC50 0.246 mg/mL. In conclusion, the tamarillo fruit may serve as a dietary antioxidant for prevention atherosclerosis and a whitening agent in cosmetics.
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