Study And Analysis Of Phenylpropanoid Phenolic Acids By Complex Chromatography

Most of various phenolic acids are compounds which similar in structure and properties. The analysis and separation of them are fairly difficult, such as using gradient elution method. Phenylpropanoid phenolic acids are compounds of conspicuous pharmacological activities,which have"Ph-C-C-C-"in structure. It takes much time to determine and separate them and the analytical methods are always complicated. The determination is often disturbed by compounds such as isomers and flavonoid glycosides which are similar in characters to phenolic acids. This article was focused on the rapid determination and separation of several pink phenylpropanoid phenolic acids by complex chromatography and analysis of coordination mechanism.It was realized that the determination selectivity was improved by the coordination difference of coordination agent and target compounds. We chose different ligands for different groups and studied the coordination mechanism, coordination sites etc by ultraviolet spectrophotometry (UV), infrared spectroscopy (IR), mass spectrography (MS) and computer model. We found certain rules from the study for a wide range of uses.1. There is certain regularity in structure of phenylpropanoid phenolic acids. The most important groups for possible coordination were"C=C"and"-COOH". If it is difficult to determine a couple of phenylpropanoid phenolic acids by routine method, we should choose suitable method according to the difference of their structure. There are two kinds of structure difference: (1) difference of"C=C"on side chain, (2) difference of"-COOH". If a couple of phenolic acids have both"C=C"and"-COOH"difference, we should judge the more important difference from the specific structure. Generally speaking argentation complex chromatography is preferred.2. We chose four ligands: AgNO3, CaCl2, borax, urea and calculated the minimum binding energy before and after coordination according to the"minimum energy principle"(MM2)by the software of ChemBioOffice 2008, and we found that the minimum energy of coordination system was lower than before. We choosed two type of ligands: metal ion (silver nitrate, calcium chloride) and nonmetal (borax, urea). The mechanism of the two type ligands is different. For metal ligands, the ability of coordination of Ag+ is stronger than Ca2+; for nonmetal ligands, the ability of coordination of borax is approximately the same to urea. The proper order of their coordination ability is Ag+>Ca2+>urea≈borax.3. We chose silver nitrate as ligand for a couple of phenolic acids which have"C=C"groups difference. The determination methods of two couples of cichoric acid and caftaric acid, salvianolic acid B and isosalvianolic acid by adding silver nitrate to mobile phase were established. The concentration of silver nitrate was from 6 to 9mmol/l. The resolutions of them were 1.5 and 2.3 respectively which were qualified according to the determination requirements. The main coordination site was on"C=C"outside the benzene ring and the coordination was strongly influenced by electron cloud of benzene ring and carbonyl (on"-COOH") nearby. The coordination was organized by n points force(n≥3).4. We chose anhydrous calcium chloride as ligand for a couple of phenolic acids which have"-COOH"difference in structure. The determination methods of salvianolic acid A and salvianolic acid B, cichoric acid and cynarin by adding calcium chloride to mobile phase were established. The concentration of calcium chloride was from 5 to 8mmol/l. The resolution were 1.9 and 1.7 respectively which were consistent with the standard of determination. The main coordination sites was on"-COOH"and the coordination was strongly influenced by electron cloud of"C=C"nearby (bigπbond of benzene ring was also involved). The effect of benzene ring was stronger than straight chain"C=C".5. If the impurities of phenolic acids sample have glucosyls, we should choose borax as the ligand. Borax can act as the inhibitor of impurities which have glucosyls. At weak acidic situation, borax preferentially coordinated with compounds which have glucosyls. It was because that glucosyls had many hydroxyl groups which could form certain hydrogen bond balance with boric acid molecule when there were more than three hydroxyl groups on the same side. The hydrogen bond balance agreed with spatial structure and was not influenced by pH.