Kyeong Hwan Hwang

Metabolic phenotyping of various tea (Camellia sinensis L.) cultivars and understanding of their intrinsic metabolism

Recently, we selected three tea (Camellia sinensis) cultivars that are rich in taste, epigallocatechin-3-O-gallate (EGCG) and epigallocatechin-3-O-(3-O-methyl)-gallate (EGCG3″Me) and then cultivated them through asexual propagation by cutting in the same region. In the present study, proton nuclear magnetic resonance (1H NMR)-based metabolomics was applied to characterize the metabotype and to understand the metabolic mechanism of these tea cultivars including wild type tea. Of the tea leaf metabolite variations, reverse associations of amino acid metabolism with catechin compound metabolism were found in the rich-taste, and EGCG- and EGCG3″Me-rich tea cultivars. Indeed, the metabolism of individual catechin compounds in the EGCG3″Me-rich cultivar differed from those of other tea cultivars. The current study highlights the distinct metabolism of various tea cultivars newly selected for cultivation and the important role of metabolomics in understanding the metabolic mechanism. Thus, comprehensive metabotyping is a useful method to assess and then develop a new plant cultivar.

Synthesis and characterization of novel astragalin galactosides using β-galactosidase from Bacillus circulans

Astragalin (kaempferol-3-O-β-d-glucopyranoside, Ast) is a kind of flavonoid known to have anti-oxidant, anti-HIV, anti-allergic, and anti-inflammatory effects. It has low solubility in water. In this study, novel astragalin galactosides (Ast-Gals) were synthesized using β-galactosidase from Bacillus circulans and reaction conditions were optimized to increase the conversion yield of astragallin. Purified Ast-Gal1 (11.6% of Ast used, w/w) and Ast-Gal2 (6.7% of Ast used, w/w) were obtained by medium pressure chromatography (MPLC) with silica C18 column and open column packed with Sephadex LH-20. The structures of Ast-Gal1 and Ast-Gal2 were identified by nuclear magnetic resonance (NMR) to be kaempferol-3-O-β-d-glucopyranosyl-(1→6)-β-d-galactopyranoside and kaempferol-3-O-β-d-glucopyranosyl-(1→6)-β-d-galactopyranosyl-(1→4)-β-d-galactopyranoside, respectively. The water solubility of Ast, Ast-Gal1, and Ast-Gal2 were 28.2±1.2mg/L, 38,300±3.5mg/L, and 38,800±2.8mg/L, respectively. The SC50 value (the concentration required to scavenge 50% of the ABTS+) of Ast, Ast-Gal1, and Ast-Gal2 were 5.1±1.6μM, 6.5±0.4μM, and 4.9±1.1μM, respectively. The IC50 values (the half maximal inhibitory concentration) of Ast, Ast-Gal1, and Ast-Gal2 against angiotensin converting enzyme (ACE) were 171.0±1.2μM, 186.0μM, and 139.0±0.2μM, respectively.

Diverse Metabolite Variations in Tea (Camellia sinensis L.) Leaves Grown Under Various Shade Conditions Revisited: A Metabolomics Study

With the increase of tea (Camellia sinensis) consumption, its chemical or metabolite compositions play a crucial role in the determination of tea quality. In general, metabolite compositions of fresh tea leaves including shoots depend on plucking seasons and tea cultivators. Therefore, choosing a specific plucking time of tea leaves can provide use-specified tea products. Artificial control of tea growing, typically shade treatments, can lead to significant changes of the tea metabolite compositions. However, metabolic characteristics of tea grown under various shade treatment conditions remain unclear. Therefore, the objective of the current study was to explore effects of various shade conditions on metabolite compositions of tea through a 1H NMR-based metabolomics approach. It was noteworthy that the levels of catechins and their derivatives were only influenced at the initial time of shade treatments while most amino acids were upregulated as amounts of shade and periods were increased: that is, the levels of alanine, asparagine, aspartate, isoleucine, threonine, leucine, and valine in fresh tea leaves were conspicuously elevated when shade levels were raised from 90% to 100% and when period of shade treatments was increased by 20 days. Such increased synthesis of amino acids along with large reductions of glucose level reflected carbon starvation under the dark conditions, indicating remarkable proteolysis in the chloroplast of tea leaves. This study provides important information about making amino acid-enhanced tea products based on global characteristics of diverse tea leaf metabolites induced by various shade treatment conditions.

Complete Genome Sequence of Chryseobacterium camelliae Dolsongi-HT1, a Green Tea Isolate with Keratinolytic Activity

ABSTRACT The complete genome sequence of Chryseobacterium camelliae Dolsongi-HT1 is reported here. C. camelliae Dolsongi-HT1, having keratinolytic activity, was isolated from green tea leaves in the Dolsongi tea garden in Jeju, South Korea. The strain Dolsongi-HT1 has 28 candidate protease genes, which may be utilized in further studies and industrial applications of keratinase.