Malic acid

The properties of the elegant spices are summarized in Table 1. L‐(+)‐Tartaric acid, formic acid, lactic acid, acetic acid, citric acid, fumaric acid, succinic acid, L‐(+)‐ascorbic acid, propionic acid, potassium dihydrogen phosphate dodecahydrate phosphate (all AR grade), and malic acid (BR grade) were obtained from Sinopharm Chemical Reagent Co. (Shanghai, China). Potassium dihydrogen phosphate (KH₂PO₄), phosphoric acid (H₃PO₄), hydrochloric acid (HCl), and disodium hydrogen phosphate dodecahydrate (Na₂HPO₄•12H₂O) (all AR grade) were purchased from Sinopharm Chemical Reagent Company (Shanghai, China). Inosine 5′‐monophosphate (5′‐IMP), adenosine 5′‐monophosphate (5′‐AMP), guanosine 5′‐monophosphate (5′‐GMP), and cytidine 5′‐monophosphate (5′‐CMP) were purchased from Sigma‐Aldrich (St. Louis). Durashell AA analytical reagents, including an internal standard solution, were purchased from Tianjin Bona Agel Technology Co., Ltd. Methanol, trifluoroacetic acid (TFA), and acetonitrile (ACN) (all HPLC grade) were purchased from Fisher Scientific (Shanghai, China). Ultrapure water was purchased from Hangzhou Wahaha Group Co., Ltd. Sulfosalicylic acid (AR grade) was obtained from Biochemical Technology Co., Ltd.