Folin ciocalteu

3-hexanone (chromatographic grade, Sigma-Aldrich); C8-C20 alkane mixture (Sigma-Aldrich); n-hexane (chromatographic grade, Ron); chloroform (AR, Sinopharm); Acetone (AR, Sinopharm); Folin-Ciocalteu (AR, Sinopharm); Gallic acid (AR, Sinopharm); Ascorbic acid (AR, Sinopharm); 2,2-diphenyl-1-picrylhydrazyl (AR, Sinopharm); 2,6-dichlorophenolindophenol (AR, Sinopharm); (+)-Catechin (AR, Sinopharm). 30 authentic volatile compound standards (Sigma-Aldrich).

GTP 1, GTP 2 and GTP 3 were all kindly supplied by the Hangzhou Tea Research Institute of All-China Federation of Supply and Marketing Cooperatives. The measurement of GTP (shown in Table 1) and wheat flour protein content referred to the AACC Method 46-12.01, 2000a [13 ]. Wheat flour (9.95% protein, 13.69% moisture) was purchased at a local supermarket (Wuxi, Jiangsu, China) and stored at 4 °C for further experiments. 1, 1-diphenyl-2-picrylhydrazyl (DPPH) was purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Total antioxidant capacity assay kits including ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) method and FRAP (ferric ion reducing antioxidant powder) method were purchased from Nanjing Jiancheng Bioengineering Institute (Nanjing, Jiangsu, China). Other reagents (Methanol, Acetone, Folin-Ciocalteu, Na₂CO₃) used in the analytical procedures were from Sinopharm Chemical Reagent Co., Ltd., China National Pharmaceutical Group Corporation (Wuxi, Jiangsu, China).

All chemicals and reagents used were of analytical grade. The water was double distilled (ddH₂O). Methanol and acetonitrile of chromatographic purity were purchased from Sigma-Aldrich (St. Louis, MO, USA). N-hexane, ethyl acetate, gallic acid, NaOH, Folin–Ciocalteu, Na₂CO₃, Trolox, 2,2-diphenyl-1-picrylhydrazyl (DPPH), FeCl₃, HCl, NaAc, and 2,4,6-tris (2-pyridyl)-s-triazine (TPTZ) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

The enzyme, human recombinant DPP-IV (Lot: D4943-1VL), expressed in baculovirus-infected S/9 cells, the substrate, Gly-Pro p-nitroanilide (Gly-Pro pNA; Lot: G0513), and streptozotocin (STZ; Lot: V900890) were purchased from Sigma-Aldrich (St. Louis, MO, USA). The antidiabetic drug sitagliptin (Januvia 100 mg; Merk Sharp and Dohme Ltd., Hertfordshire EN11 9BU, Hertford Road, Hoddesdon, UK) was purchased at a drugstore in China. Other reagents, such as Folin–Ciocalteu (Lot: 73104861), gallic acid (Lot: XW01499171), and Coomassie Blue R-250 (Lot: 71011381) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Lapsang souchon (LS), a typical Chinese black tea, was obtained from a tea market in Hangzhou.

Aloe vera (Aloe vera (L.) Burm.f.) leaves were provided by Tongxiang Huimei Aloe planting Cooperative (Jiaxing, China). Lactobacillus plantarum powder was obtained from Guozhen Health Science and Technology (Beijing) Co., Ltd. (Beijing, China). The Princess Fermented beverage (PFB) was purchased from Rivaland Co., Ltd. (Suzuka City, Mie Prefecture, Japan). Folin-Ciocalteu, NaOH, and Al(NO₃)₃ were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Palmitic acid (PA) was from Sigma (St. Louis, MO, USA). Bovine serum albumin (BSA), Dulbecco’s modified Eagle’s medium (DMEM), and fetal bovine serum (FBS) from BBI Solutions (Shanghai, China) were used in cell culture. Cell Counting Kit-8 (CCK-8) was from MedChemExpress (Monmouth, NJ, USA). The 4% paraformaldehyde, Hematoxylin and Eosin Staining Oil (H&E) and Red O kit were purchased from Beyotime (Nantong, China), while the Mayer’s Hematoxylin was from Sbjbio (Nanjing, China). Furthermore, serum interleukin 10 (IL-10) and tumor necrosis factor alpha (TNF-α) kits were from Shanghai Enzyme-linked Biotechnology Co., Ltd. (Shanghai, China). The E.Z.N.A. ^® soil DNA Kit and the AxyPrep DNA Gel Extraction Kit were from Omega Bio-Tek (Norcross, GA, USA) and Axygen Biosciences (Union City, CA, USA) respectively.