Bc1230

Ascorbic acid (AsA) content was quantified via an assay kit (Solarbio, BC1230) at 265 nm based on the reaction between ascorbate oxidase and AsA to form dehydroascorbic acid, meanwhile assay kit (Solarbio, BC1170) was used for the reduced glutathione (GSH) content. GSH undergoes a reaction with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) to form 2-nitro-5-mercaptobenzoic acid and glutathione disulfide and the absorbance was read at 412 nm. The plant flavonoids were determined with a colorimetric assay kit (Solarbio, BC1330) at 470 nm, and the plant total of phenol was measured by the Folin-Ciocalteu method according to the manufacturer’s instructions at 760 nm (Solarbio, BC1340). ASA and GSH were extracted in 0.1 g of fresh leaf samples with 1 mL of extraction solution given by the assay kits. The total phenol was extracted with 2.5 mL of 60% alcohol and the flavonoids with 1 mL of 60% ethanol.

A commercial kit (BC1230, Solarbio) was applied to determine AsA content based on the oxidation rate of AsA catalyzed by AAO (ascorbic acid oxidase) (spectrophotometric measurement at OD_{265 nm}). A commercial kit (BC1240, Solarbio) was applied to determine DHA content based on the production rate of AsA from DHA by DTT (1,4-dithiothreitol) (spectrophotometric measurement at OD_{265 nm}). A commercial kit (BC1170, Solarbio) was applied to determine GSH content based on spectrophotometric measurement of the product from the reaction between GSH and DTNB (5,5’-dithiobis-2-nitrobenoic acid) (OD_{265 nm}). A commercial kit (BC1180, Solarbio) was applied to determine GSSG content based on the production rate of GSH (measurement of OD_{265 nm} for the reaction between GSH and DTNB) from GSSG catalyzed by GR (GSH reductase). A commercial kit (BC0290, Solarbio) was applied to determine proline content based on spectrophotometric measurement of the product from the reaction between proline and ninhydrin (OD_{520 nm}). A commercial kit (BC0035, Solarbio) was applied to determine plant soluble sugar content based on anthrone colorimetric method (OD_{620 nm}). A commercial kit (BC0700, Solarbio) was applied to determine starch content based on the separation of starch with 80% ethanol and acid hydrolyzation to glucose, followed by anthrone colorimetric method (OD_{620 nm}) (Chen et al., 2020b (link)).

AsA content was measured with an ascorbic acid activity test kit (BC1230, Beijing Solarbio, Beijing, China). Two grams of potato-sample extract was blended with 2 mL of extracting solution. After being centrifuged (8000 r/min), for the determination tube, 0.1 mL of extract was mixed with 0.9 mL of intricate solution, consisting of 0.5 mL metaphosphoric acid–acetic acid solution (0.1 g/mL), 0.1 mL of 5% sulfuric acid, and 0.3 mL of ammonium molybdate solution (0.05 g/mL). The standard tube used 100 μL of standard liquids instead of sample. After mixing, then, both measurement and standard tubes accurately transferred 1 mL to a quartz colorimetric utensil. Absorbance was read at 265 nm.AsA activity was expressed in nmol/g of fresh tissue weight (nmol/g FW).