Glycolic acid

Choline chloride (ChCl, 98%, CID: 6209), urea (99%, CID: 1176), citric acid (≥99.5%, CID: 311), malic acid (99% CID: 525), ethylene glycol (98%, CID: 174), malonate (99.5%, CID: 9084), glycolic acid (98%, CID: 757), and ethanol (EtOH, 99.9%, CID: 702) were of analytical grade and acquired from Macklin Biochemical Co., Ltd. (Shanghai, China). 1,2-propanediol (AR, ≥99.5%, CID: 1030), vitamin C (VC), DPPH free radical scavenging capacity assay kit, and ABTS free radical scavenging capacity assay kit were purchased from Solarbio Science & Technology Co., Ltd. (Beijing, China). Methanol (CID: 887), acetic acid (CID: 176), water (CID: 962), vitexin (CID: 5280441), and isovitexin (CID: 162350) were of chromatographic grade and acquired from Aladdin (Shanghai, China).

Glycerol was purchased from Sinopharm (Beijing, China), NAD⁺ was purchased from MesChemExpress (Shanghai, China), 1,3-dihydroxyacetone (DHA) and O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) for HPLC derivatization were purchased from Bidepharm (Shanghai, China), lactic acid was purchased from Aladdin (Shanghai, China), sodium chlorite and glycolic acid were purchased from Macklin (Shanghai, China), Acetonitrile was purchased from Innochen (Beijing, China), isopropyl-beta-D-thiogalactoside (IPTG) (inducer, > 99%) was purchased from Solarbio (Beijing, China), Ampicillin was purchased from Inalco (Beijing, China) and Kanamycin was purchased from Aladdin (Shanghai, China). Oligonucleotide syntheses and DNA sequencing analyses were carried out by Genewiz (Tianjin, China). Seamless Cloning Kit was purchased from Beyotime (Shanghai, China). The amount of DNA in cloning experiments was quantified by TECAN microplate reader (Infinite M200, TECAN, Switzerland).

The Ginkgo biloba leaves picked on May were purchased from Chinese Herb Transaction Center (Bozhou, China). The leaves were dried at 40 °C to constant weight in vacuum oven, and then pulverized to 30–40 mesh by a disintegrator. The water content of the Ginkgo biloba leaves powder was 3.17% (w/w).
The standards of SA (≥99.0%), PA (≥99.0%), GAA (≥99.0%) and PHBA (≥99.0%) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai, China). The 6-HKA (≥99.8%) was donated by Zhejiang Conba Pharmaceutical Co., Ltd (Hangzhou, China). Choline chloride (≥98.0%), citric acid (≥99.5%), d-sorbitol (BR) were purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). Phosphorous acid (chromatographic grade, 85–90%), dl-malic acid (≥99.0%), malonic acid (≥99.0%), levulinic acid (≥99.0%) and 2-pyrrolidinecarboxylic acid (≥99.0%) were obtained from Aladdin Chemistry Co., Ltd (Shanghai, China). Glycolic acid (≥98.0%), xylitol (≥99.0%) and betaine (≥99.0%) were acquired from Shanghai Macklin Biochemical Co., Ltd (Shanghai, China). Acetonitrile (chromatographic grade) was purchased from Tedia Company, Inc. (Shanghai, China). Deionized water was obtained by a Milli-Q water purification system (Millipore, Billerica, MA, USA). All other reagents and chemicals used in this work were of analytical reagent grade.