Gallic acid

According to the previous study on the composition of the exudate droplets of Sclerotinia, eight related organic acids were selected as reference. The reference compounds were oxalic acid (o2si, Charleston, SC, USA), gallic acid, ferulic acid, vanillic acid, chlorogenic acid, tannic acid (ANPEL, Shanghai, China), cinnamic acid (CNW, Duesseldorf, Germany), and caffeic acid (Dr. Ehrenstorfer GmbH, Augsburg, Germany). The purity of these ingredients was >98% as determined by HPLC. For the oxalic acid component of the sample, the chromatographic system was controlled by an Agilent 1260 series HPLC chromatograph equipped with an Athena C₁₈-WP column (2.1 × 150 mm, 3 µm). After diluting the sample 10 times, 5 µL sample was injected. The sample was separated using 0.1% phosphoric acid as the mobile phase (flow rate, 1.0 mL/min) for 15 min at a column temperature of 35 °C. The wavelength of the UV–visible detector was set at 210 nm. To detect the other seven compounds, the sample was passed through an Agilent 1260 series HPLC chromatograph equipped with an Innoval ODS 2 column (4.6 × 150 mm, 5 µm). Separation was carried out under the following chromatographic conditions: injection volume, 10 µL; column temperature, 35 °C; UV detection wavelengths, 265 nm and 323 nm; mobile phase, 0.1% phosphoric acid and acetonitrile with gradient elution at a flow rate of 1.0 mL/min.

Sodium chloride, methanol, ethanol, amino acid standards, acetonitrile, phenyl isothiocyanate, gallic acid, triethylamine, n-hexane, boron trifluoride-methanol, dichloromethane, formic acid, diethyl ether, petroleum ether, sodium hydroxide, potassium hydroxide, hydrochloric acid, and perchloric acid were purchased from ANPEL Laboratory Technologies (Shanghai) Inc. Vitamin B1/B2 and vitamin E were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. Folin-Ciocalteu reagent, 2,2-diphenyl-1-picrylhydrazyl (DPPH), mixed standards of fatty acids, cyanidin 3-O-glucoside, anthranone, 1,2,3-trihydroxybenzene, benzoyl-dl-arginine p-nitroanilide hydrochloride, dimethyl sulfoxide, sulfosalicylic acid, trypsin, and phytic acid were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). The purity of chemicals used for High-Performance Liquid Chromatography (HPLC) and Gas Chromatography Mass Spectroscopy (GCMS) complied with the requirement of relevant procedures. All other chemicals were of analytical grade.

Jujube fruit (Ziziphus jujuba Mill. cv. Junzao) was harvested in December 2020 in Hotan, Xinjiang province (latitude, 79°18′22″; longitude, 37°13′9″). The local climate is temperate continental desert with a high temperature and dry climate, and the annual average rainfall is <50 mm. Approximately 10 kg of dry mature jujube fruit (wet base moisture content, 21%) was collected in foam boxes covered with ice. The samples were sent to the laboratory at Xinjiang Shihezi University within one day. The screened samples were cleaned with double-distilled water (ddH₂O), and stored in a dry and odorless cold storage at 4 °C until drying and analysis were complete.
Caffeic acid, ferulic acid, phloroglucinol, cinnamic acid, chlorogenic acid, p-hydroxybenzoic acid, p-coumaric acid, vanillic acid, gallic acid, catechin, protocatechuic acid, epicatechin, rutin, quercetin, and procyanidins B1 and B2 were obtained from Anpel Co. (Shanghai, China). A total of 37 fatty acid mixed standards, 17 amino acid mixed standards, asparagine, glutamine, citrulline, valine, tryptophan, and 21 hydroxyproline and sarcosine standards were obtained from Sigma Aldrich (St. Louis., Mo, USA).