Separation and determination of D-malic acid enantiomer by reversed-phase liquid chromatography after derivatization with (R)-1-(1-naphthyl) ethylamine

Abstract L-Malic acid is the Active Pharmaceutical Ingredient of the latest generation of compound electrolyte injection (STEROFUNDIN ISO, Germany) and plays a very important role in the rescue of critically ill patients. The optical purity of L-malic acid is a Critical Quality Attributes. A new reversed-phase high performance liquid chromatography (RP-HPLC) method for pre-column derivatization of D-malic acid enantiomer impurity in L-malic acid bulk drug was established. The derivatization reaction was carried out using (R)-1-(1-naphthyl)ethylamine ((R)-NEA) as a chiral derivatization reagent. The Kromasil C18 column was used with a detection wavelength of 225 nm, a flow rate of 1.0 mL·min-1, and a column temperature of 30 °C. The mobile phase was acetonitrile-0.01 mol·L-1 potassium dihydrogen phosphate solution (containing 20 mmol·L-1 sodium heptanesulfonate, adjusted to pH 2.80 with phosphoric acid) (at a ratio of 45:55) and the resolution of D-malic acid and L-malic acid derivatization products reached 1.7. The proposed method possesses the advantages of simple operation, mild conditions, stable derivatization products and low cost. Also it gave better separation and was more accurate than previous methods

Reducing Allergenicity to Arginine Kinase from Mud Crab Using Site-Directed Mutagenesis and Peptide Aptamers.

The mud crab ( Scylla paramamosain) is widely consumed but can cause a severe food allergic reaction. To reduce allergenicity to arginine kinase (AK), site-directed mutagenesis was used to destroy disulfide bonds or mutate critical amino acids of conformational epitopes. Three hypoallergenic mutant AKs (mAK1, mAK2, and mAK3) were generated, with the immunoreactivity decreasing by 54.2, 40.1, and 71.4%, respectively. In comparison to recombinant AK (rAK), the structure of mAKs was clearly changed. Additionally, antisense peptides were designed on the basis of linear epitopes and pepsin-cutting sites of AK. Five peptide aptamers were screened by molecular docking and then analyzed by the immunoglobulin E inhibition enzyme-linked immunosorbent assay and human Laboratory of Allergic Diseases 2 mast cell degranulation assay. The peptide aptamers could significantly inhibit allergenicity of rAK and mAKs, and the inhibitory effect of peptide aptamer 3 was slightly better than the others. These results provide synergistic methods to reduce allergenicity to AK, which could be applied to other shellfish allergens.

Analysis of the Allergenic Epitopes of Tropomyosin from Mud Crab Using Phage Display and Site-Directed Mutagenesis.

Mud crab ( Scylla serrata), which is widely consumed, can cause severe allergic symptoms. Eight linear epitopes and seven conformational epitopes of tropomyosin (TM) from S. serrata were identified using phage display. The conformational epitopes were formed based on the coiled-coil structure of TM. Most of the epitopes were located in the regions where primary structures were conserved among crustacean TM. Twelve synthetic peptides were designed according to the epitopes and trypsin-cutting sites of TM, among them, three synthetic peptides (including one linear epitope and two conformational epitopes) were recognized by all of the patient sera using inhibitory dot blotting. A triple-variant (R90A-E164A-Y267A) was constructed based on the critical amino acids of the TM epitope. The IgE-binding activity of the triple-variant was significantly reduced compared with that of native TM. The results of phage display and site-directed mutagenesis offered new information regarding conformational epitopes of TM.