2 2 diphenyl 1 picrylhydrazyl (dpph)

DL-α-Lipoic acid (LA) (>99.0%) (CAS 1077-28-7) was purchased from Tokyo Chemical Industry Co., LTD (Tokyo, Japan). (±) α-Lipoamide (LPA) (96%) (CAS 940-69-2) was purchased from Toronto Research Chemicals (Toronto, ON, Canada). Tetraethoxysilane (TEOS) (ECOS, high purity grade, Moscow, Russia), ethanol (EtOH) (95%, Chimmed, analytical grade, Moscow, Russia), (3-mercaptopropyl)trimethoxysilan (MPTMOS) (95%) (CAS 4420-74-0), (Aldrich, St. Louis, MO, USA), (3-aminoporopyl)triethoxysilane (APTEOS) (99%) (CAS 919-30-2) (Aldrich, Kenilworth, NJ, USA), methyltrimetoxysilane (MTMOS) (98%+)(CAS 1185-55-3) (Acros Organics, New Jersey, NJ, USA), and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (CAS 1898-66-4) (Tokyo Chemical Industry Co., LTD, Tokyo, Japan) were used without further purification. Sodium dihydrogen phosphate (NaH₂PO₄·2H₂O) and disodium hydrogen phosphate (Na₂HPO₄·12 H₂O) (Chimmed, analytical grade, Moscow, Russia) were used to prepare buffer solutions with pH 6.0, 6.5, 6.8, and 7.4. Citric acid (Chimmed, analytical grade, Moscow, Russia), sodium hydroxide (Chimmed, analytical grade, Moscow, Russia), and hydrochloric acid (Acros, for analysis, 37%, Geel, Belgium) (CAS 7647-01-0) were used to prepare buffer solution with pH 1.6. The buffer solutions were prepared using doubly distilled deionized water.

Nanfeng mandarins, Xunwu mandarins and Yangshuo kumquats were purchased from local fruit market in Ganzhou city in Jiangxi Province in November 2019. A physiological drop of Gannan Newhall navel oranges was collected from the orchard of Gannan Normal University in June 2019.
2,2-Diphenyl-1-picrylhydrazyl (DPPH) was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan), 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and n-alkanes (C₈–C₂₀) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Butylatedhydroxytoluene (BHT) was purchased from Macklin, Shanghai, China. Ampicillin (sodium salt) was purchased from Solarbio, Beijing, China. The following microorganisms were purchased from Beijing, China General Microbiological Culture Collection Center (CGMCC): Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923), Bacillus subtilis (ATCC6633), Salmonella typhimurium (ATCC14028) and Pseudomonas aeruginosa (ATCC9207).

Cold-pressed Marsh white grapefruit (Citrus paradisi Macf., Lakeland, FL, USA) EO was purchased from Ungerer Limited. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), n-alkanes(C8–C20)were purchased from Sigma-Aldrich (St. Louis, MO, USA). Butylated hydroxytoluene (BHT) was purchased from Macklin, Shanghai, China. The following microorganisms were purchased from Beijing, China General Microbiological Culture Collection Center (CGMCC): Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923), Bacillus subtilis (ATCC6633), Salmonella typhimurium (ATCC14028), and Pseudomonas aeruginosa (ATCC9207).

Vanillin
(V) (99%), ethylene carbonate (EC)
(98%), potassium carbonate (K₂CO₃) (≥99%), N,N-dimethylformamide (DMF) (≥99%),
methacrylic anhydride (MAA) (94%), ethylenediamine (ED) (≥99%),
2,2′-(ethylenedioxy)bis(ethylamine) (Dom) (>97%), phenylbis(2,4,6-trimethylbenzoyl)phosphine
oxide (BAPO) (97%), and deuterium dimethyl sulfoxide (DMSO-d₆) (99.9% atom % D) were purchased from Sigma-Aldrich
and used without any additional purification. 4-(Dimethylamino)pyridine
(DMAP) (≥99.0%, Fluka), magnesium sulfate (99%, VWR), sodium
bicarbonate (≥99%, Merck), sodium hydroxide (NaOH) (≥99%,
Fisher Scientific), ethyl acetate (EtOAc) (≥99%, VWR), dichloromethane
(DCM) (≥99%, Fisher Scientific), hydrochloric acid (HCl) (37%),
and acetone (≥99.5%, VWR) were all used as received. Sodium
lignosulfonate for the coating of the thermosets and 2,2-diphenyl-1-picrylhydrazyl
(DPPH°) for the antioxidant assay were acquired from Tokyo Chemical
Industry Co., Ltd.

Fourteen batches of CRC leaves were collected from different areas of Guangdong province in China for analysis, and the detailed information is listed in Table 1. The leaves were dried (60°C), reduced to coarse homogeneous powders, and stored in sealed containers at ambient temperature until required. Samples were authenticated by Prof. Kang Chen (College of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China).
Four reference compounds (≥98% purity) such as hesperidin, tangeretin, nobiletin, and 5-demethylnobiletin were obtained from Guangzhou Institute of Drug Control (Guangzhou, China); L-ascorbic acid was purchased from Damao Chemical Reagent Factory (Tianjin, China); and DPPH (≥97% purity) was obtained from Tokyo Chemical Industry Co., Ltd. (Shanghai, China).
Chromatographic grade acetonitrile was purchased from Merk (Darmstadt, Germany); ultrapure water was prepared in-house (18.2 MΩ·cm; Sichuan Zhuoyue Water Treatment Equipment Co., ltd., Sichuan, China); ethanol and phosphoric acid (analytical grade) were purchased from Merk (Darmstadt, Germany) and Tianjin Kemiou Chemical Reagent Co., Ltd. (Tianjin, China), respectively.

PAN powder (Mw = 150,000 g/mol) and Alkali lignin (low sulfonate content: ≤3.6%) were purchased from Sigma-Aldrich, Tokyo, Japan. N,N-Dimethylformamide (DMF 99.8%) and silver nitrate (AgNO₃) were purchased from Wako Pure Chemical Industries, Osaka, Japan. DPPH (1, 1-diphenyl-2-picryl hydrazyl radical) was purchased from Tokyo Chemical Industry Co., Ltd, Japan. Distilled water was used from the laboratory water distillation plant. All chemicals were used without any further purification.