Ascorbic acid

To evaluate the antiradical activity of MCGP, 25–1,000 µM of MCGP was placed in 96-well plates (Corning, NY, United States), and 130 µl of 2,20-AzinoBis-(3-ethylbenzoThiazoline-6-Sulfonic acid) (ABTS^•+) (Macklin, Shanghai, China) radicals was added. The ABTS^•+ reagent was produced by reacting the ABTS solution (10 mM) with 30% H₂O₂ in advance. After incubation for 16 h at room temperature, 10 ml of this solution was diluted in 80 ml of sodium acetate hydrochloric acid buffer (Macklin, Shanghai, China). Ascorbic acid (25–1,000 µM) (Macklin, Shanghai, China) was used as a standard antioxidant. After 30 min of incubation in the dark at room temperature, the plates were read at 650 nm using a microplate reader (Thermo Fisher Scientific, United States).

All chemicals were used without further purification. Copper (II) chloride (CuCl₂), copper sulfate pentahydrate (CuSO₄·5H₂O), ascorbic acid (AA), sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium chloride (NaCl), ethanol (>99.7%), isopropanol (>99.7%), diethanolamine (DEA > 99%), ethylene glycol (EG > 99%) were purchased from Macklin. Polyvinylpyrrolidone (PVP, K29-K32) and Nafion (5 wt%) were purchased from Sigma-Aldrich. Activated carbon (Vulcan XC-72) was obtained from SCI Materials Hub. Deionized (DI) water was used throughout the experiments.

All the chemicals were of analytical grade and used as purchased without further purification. Copper foil (thickness of 0.1 mm) were supplied by Hebei Jinjia Metal Materials Ltd. Co (P. R. China). HAuCl₄, sodium hydroxide, glucose, dopamine, ascorbic acid, uric acid, sucrose, lactose, and maltose were supplied by Macklin Inc, Shanghai, China. The Cu foil was anodized in an alkali solution (3 M NaOH) for 30 min under 10 mA cm^-2 to form Cu(OH)₂ nanowire. The temperature of the electrochemical cells was maintained at 25 °C for all experiments. The as-anodized nanowire was annealed at 180 ^oC for 1 h to converted Cu(OH)₂ to CuO. The nanowire arrays were dipped into HAuCl₄ solution (pH = 6.0) under simulated solar light irradiation (100 mW cm^-2) for 30 min for Au deposition.

Acetonitrile, formic acid, and methanol (HPLC grade) were supplied from Fisher (Fairlawn, NJ, USA). The standards (purities > 95%) used for identification and quantification of flavonoids: (+)-catechin (Ca), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-gallocatechin (GC) and (-)-epicatechin-3-O-galate (ECG), quercetin-3-O-glucoside, and malvidin-3-O-glucoside were purchased from Extrasynthese (France), myricetin-3-O-galactoside, kaempferol-3-O-galactoside, kaempferol-3-O-glucoside, syringetin-3-O-glucoside, isorhamnetin-3-O-glucoside were purchased from Push Bio-technology (Chengdu, China). Other analytical grade chemical reagents, such as phloroglucinol, sodium acetate, ascorbic acid, NaOH, HCl, methanol, acetone, were supplied from Macklin Biochemical (Shanghai, China).

The silicon wafer was n-type (100), resistivity < 0.01 Ω·cm, 550 μm thick, purchased from Henan Micro-Nano Semiconductor Company. AZ4620 photoresist, developer, and magnetron targets were also purchased from the company. Sodium chloride (99.7%), sodium hydroxide (95%), glucose (99.7%), concentrated sulfuric acid (98%), and CTAB (99%) were purchased from Sinopharm. Copper sulfate pentahydrate (99.7%), sucrose (99.9%), ascorbic acid (AA, >99.0%), and uric acid (UA, 99%) were purchased from Macklin. Fructose (99%) provided by Aladdin. Deionized water was self-made in the lab.

Wild rice Z. latifolia was collected from Jiangling County, Jingzhou City, Hubei Province, China (30°13′10″ N; 112°34′5″ E), in September 2017. The sample was obtained by manually harvesting mature plant tassels, drying and then dehulling them to obtain the seeds. The seeds were ground to a fine powder in a mechanical grinder and then sieved through a 0.45 mm sifter.
(+)-Catechin (C), (−)-epicatechin (EC), and (−)-epigallocatechin (EGC), DPPH (2,2-diphenyl-1-picrylhydrazyl), α-glucosidase (type I, from Saccharomyces cerevisiae), and pancreatic lipase (type II, from porcine pancreas) were purchased from Sigma-Aldrich Chemical Co., (St. Louis, MO, USA). Ascorbic acid, acarbose, and orlistat were obtained from Macklin Biochemical Co., Ltd. (Shanghai, China). Phloroglucinol was from Aladdin Reagents Co., Ltd. (Shanghai, China). HPLC and LC–MS grade solvents were bought from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The D101 macroporous resin and Sephadex LH-20 were from Solarbio Science & Technology Co., Ltd. (Beijing, China) and GE Healthcare Bio-Sciences AB (Uppsala, Sweden), respectively. Precoated silica gel plates (GF254, Qingdao Marine Chemical Co., Ltd., Qingdao, China) were used for thin layer chromatography (TLC) analysis, and spots were visualized by spraying with anisaldehyde-sulfuric acid agent.