Vanillin

C. oleifera Abel. seed meal (variety: Changlin 3) was provided by Jiangxi Zhongye Tea Technology Co., Ltd (Jiangxi, China). (Approval Number SC10236112411503).
Raw material treatment was as follows: C. oleifera Abel. seed meal was pulverized (Disintegrator, 103B, Rui’an Yongli Pharmaceutical Machinery Co., Ltd., Rui’an, China), and dried by passing it through a 60-mesh screen (GB/T6003, Shaoxing Jinhang Instrument Co., Ltd., Shaoxing, China), followed by decreasing and drying with petroleum ether, with a moisture content of < 6% [35 (link)].
C. oleifera saponins (purity, ≥98%) were purchased from Solarbio Corporation (Beijing, China). Anhydrous methanol, concentrated sulfuric acid, petroleum ether (60–90), ammonium bicarbonate, acetone, phosphoric acid, and sodium hydroxide were purchased from Xilong Science Co., Ltd (Shantou, China). Vanillin, N-Propanol, and calcium oxide were purchased from Tianjin Damao Chemical Reagent Factory (Tianjin, China). Ammonium sulphate was purchased from Daduhe Road Company (Chengdu, China). All other chemicals were of analytical grade except ammonium sulfate and hydrochloric acid.

(+)-Catechin, 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,4,6-tri (2-pyridyl) -s-triazine (TPTZ), 6-hydroxy-2,5,7,8-tetramethlchroman-2 -carboxylic acid (Trolox), gallic acid, Folin-Ciocalteu reagent, aluminum chloride hexahydrate (AlCl₃·6H₂O), methanol, vanillin, concentrated hydrochloric acid, potassium persulphate (K₂S₂O₈), phosphate buffer saline (PBS), sodium acetate trihydrate, glacial acetic acid, ferric chloride (FeCl₃·6H₂O), ferrous sulfate (FeSO₄·7H₂O) and acetone were purchased from Tianjin Damao Chemical Reagent Co., Ltd. (Tianjin, China). Absolute ethanol was procured from Tianjin Fuyu Fine Chemical Co., Ltd. (Tianjin, China). Trifluroacetic acid (TFA), acetonitrile (HPLC grade), and methanol (HPLC grade) were purchased from Sigma-Aldrich Co., Ltd. (Shanghai, China).