Synthesis of <i>Capsicum chinense</i> Citric Acid Esters-Its Methanol Trans-esterification Investigations with hplc Analysis and Its valorization as Gels-Crystals Ca-Salts

Abstract

The esterification between citric acid molecules and raw material-<i>Capsicum chinense</i> organic molecules in excess was carried out at 137°C-410.15°K. The kinetics of the reaction showed that this reaction was second order compared with citric acid and the calculated initial and global speed constant were respectively 1.43×10^-1[L²×mol^-2×s^-1] and 3.84×10^-2 [L²×mol^-2×s^-1]. The synthesized raw material’s-<i>Capsicum chinense</i>’s citric acid esters solutions colors was from light yellow-1.5[mn] to highly orange yellow-60[mn] confirming the esterification between citric acid molecules and the main bioactive molecules constituting the Capsicum chinense including capsaïcine, quercetin and luteolin whose densities were superior to one and explained the high densities of the Capsicum chinense citric acid esters solutions between 0.9825[g/ml] to 1.0636[g/ml]. Then, the alkene concentrations in esters solutions recorded an increase initially and at the middle of the time reaction respectively due to citric acid dehydration and alkenes from the raw material’s-<i>Capsicum chinense</i>’s bioactive molecules. But, the diminution of these alkene concentrations recorded from 900[s] time reaction confirmed their etherification with carboxylic acid and/or alcohol organic functions catalyzed by citric acid’s protonic acid-H⁺. Second, the trans-esterification mechanisms of the raw materials’ citric acid esters solutions with methanol was explored, inventoried and carried out in order to extract its bioactive molecules and their derivatives synthesized during this trans-esterification reaction where citric acid’s protonic acid-H⁺ sites functioned as catalyst. Thus, a trans-esterification using reflux-assembly followed by an extraction procedures were established in this manuscript. Indeed, the hplc analysis of the dichloromethane extracts allowed to identify the <i>Capsicum chinense</i>’s bioactive molecules and these derivatives. Third, procedures to synthesize crystals and gel calcium salts of raw material’s citric acid esters solutions was established. An inventory of these gel-crystals structure was done in this manuscript and it was deduced that the first step of these procedures was the esters solution titration with NaOH-0.05N in order to determine the optimum quantities of calcium hydroxide for the synthesis using reflux assembly at 137°C followed by evaporations procedures. Then, once synthesized gel was suffered under thermic treatment until having solid crystals well-structured, both could be characterized by an established EDTA-0.01N and alkene procedures titrations established in this manuscript. Finally, an established titration procedure with NaOH-0.05N allowed to determine their equivalent citric acid molecules concentrations. It was noticed that their citric acid and calcium weight concentration ratio was respectively 4.354/1.67 (≈2/1) which confirmed the well-structured of the product regarding to the exploration salts synthesis-mechanisms figures done in this manuscript.