• Korean Journal of Plant Tissue Culture
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• v.28 no.5
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• pp.231-237
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• 2001

A cDNA clone encoding metallothionein-like protein (CitMT45), which was reported by Moriguchi et al. (1998), was isolated from Citrus fruits cDNA library through differential screening. Our cDNA clone has longer 5'untranslated region, compared to it isolated by Moriguchi et al. (1998). RNA blot analysis showed that the mRNA was abundant in fleshes than peels, leaves, and flowers, as a single transcript. However, regardless of tissue types, the blots showed the similar expression patterns in the process of development with some different profile. These results suggest that CitMT45 may play important roles in the development and/or senescence of various tissues of Citrus. A genomic clone corresponding to CitMT45 was isolated and found to have three exons and two introns. A primer extension analysis suggested that the transcription of CitMT45 gene was started at three start sites with different degrees. The 5'-flanking region was shown to contain a putative metal regulatory element (MRE) and low- temperature responsive element which suggests the possibility of metal-and cold-regulated transcription, respectively.

• Food Science and Preservation
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• v.30 no.2
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• pp.235-246
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• 2023

Yellowball (Citrus hybrid cv. Yellowball ) is a new citrus hybrid between Haruka (C. tamurana × natsudaidai ) and Kiyomi (C. unshiu × sinensis) and is known to possess strong antioxidant activity. However, detailed information on the antioxidant components of its peel has not yet been reported. This study evaluated the antioxidant activity of the peel and identified the antioxidant components by fractionating a methanolic extract of Yellowball peels using liquid-liquid extraction with n-hexane, ethyl ether (ether), ethyl acetate (EA), butanol, and water. The phenolic contents and antioxidant activities of the n-hexane, ether, and EA fractions were higher than those of the other fractions, and these fractions were further separated by semi-preparative high-performance liquid chromatography (HPLC). Four antioxidant peaks, EA1, EA2, EA3, and He1, were isolated and analyzed using ultra-performance liquid chromatography-quadrupole-time- of-flight mass spectrometry (UPLC-Q-TOF MS). Sinapoyl glucoside and hesperidin were identified in EA2 and EA3, respectively, and a polymethoxylated flavone (PMF) complex (5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone, natsudaidain, tetrameth- oxyflavone, and tangeretin) was identified in He1. A compound in EA1 with m/z 223.0246 [M-H] could not be identified and was named unknown2. The antioxidant activity of unknown2 (IC₅₀=69.17 ㎍/mL) was similar to that of Trolox, which was noted as a major antioxidant in Yellowball peel. Further studies on the antioxidant capacity of Yellowball peel are required; however, these results provide a foundation for using Yellowball peel as an antioxidant.