Epigallocatechin gallate

Amber was crushed, powdered, and extracted twice with 50% ethanol at a temperature of 40 °C for 1 h. The filtrate was then freeze dried to obtain a powder. Amber extract was then dissolved in Dimethyl sulfoxide (DMSO; Kanto Chemical Co., Tokyo, Japan) at a stock concentration of 100 mg/mL, stored at −80 °C and supplied by Kohaku Biotechnology Co., Ltd., Tsukuba, Japan.
For treatment, AE was mixed with E. coli OP50 to obtain respective final concentrations of 5, 25 and 50 µg/mL at 5% DMSO and spread on Nematode Growth Medium (NGM) plates. For a control, 5% DMSO was employed.
5′-Fluorodeoxyuridine (FUDR), Ampicillin Sodium salt, Dichlorofluorescin diacetate (DCFHDA), Epigallocatechin gallate (EGCG) and Nile red were obtained from FUJIFILM Wako Pure Chemical Industries, Ltd., Osaka, Japan. Cortisone and Hydrogen peroxide were purchased from Sigma-Aldrich, St. Louis, MO, USA. Additionally, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) was also purchased from Cayman Chemical Company, Ann Arbor, MI, USA.

Aluminum nitrate nonahydrate, aluminium chloride, 2,2-diphenyl-1-picryl-hydrazyl (DPPH), ferric chloride, ferrous sulfate, gallic acid, Folin–Ciocalteu’s reagent, 3,5-dinitrosalicylic acid, hydrogen peroxide, potassium dihydrogen phosphate, potassium ferricyanide, sodium salicylate, sodium carbonate, sodium nitrite, trichloroacetic acid, amino acids [alanine (Ala), aspartic acid (Asp), arginine (Arg), histidine (His), gamma-butyric acid (GABA), lysine (Lys), glutamic acid (Glu), serine (Ser), threonine (Thr), theanine (Thea), tyrosine (Tyr)], and caffeine were obtained from Sigma Chemical Co. (St. Louis, MO, USA). Catechins [(+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechingallate (ECG), and (-)-epigallocatechin gallate (EGCG)] and theaflavins [theaflavin (TF), theaflavin-3-gallate (TF3G), and theaflavin-3’-gallate (TF3’G)] were obtained from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). All other chemicals and solvents used were of standard analytical grade.

Methyl gallate (MG), epicatechin gallate (ECg) epigallocatechin gallate (EGCg) catechin gallate (Cg), and gallocatechin gallate (GCg), used as substrates for enzyme assay of tannases, were obtained from Wako Pure Chemical Industries., Ltd. (Osaka, Japan). In addition, (−)-epigallocatechin-3-O–(3-O–methyl) gallate (EGCg3″Me) was purchased from Nagara Science (Gifu, Japan). Structures of substrates are shown in Additional file 1: Figure S1. All substrates were dissolved in 50 mM phosphate buffer (pH 6.8) containing 1% ascorbic acid (Wako) at a final concentration of 0.5 mM or 1 mM.

Chrysin, luteolin, daidzein, genistein, epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCG), tangeretin, nobiletin, and U0126 were obtained from Wako Pure Chemical Industries, Ltd. (Saitama, Japan). Flavone, 7-hydroxyFlavone, baicalein, galangin, and quercetin were obtained from Sigma-Aldrich (St. Louis, MO, USA). 5-hydroxyFlavone, apigenin, kaempferol, and myricetin were obtained from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). All reagents were dissolved in dimethyl sulfoxide (DMSO) obtained from nacalai tesque, inc. (Kyoto, Japan). It was 100 fold dilution in culture medium, and final DMSO concentration was 0.25%.