Phenolic compounds from Syzygium cumini (L.) Skeels leaves: Extraction and membrane purification

A hybrid process consisting of extraction and microfiltration was proposed in this study for producing purified, clear and stable aqueous phenolic extract from jamun (Syzygium cumini (L.) Skeels) leaf. Response surface methodology was successfully used for optimization of extraction conditions. Pseudo-first order kinetic model successfully described the extraction of total polyphenols from jamun leaves, with the activation energy determined as 9.5 kJ/mol based on the Arrhenius model. The kinetic constants were used to study the kinetic and thermodynamic compensations of extraction of TPC from jamun leaves. Applying the statistical criterion, the kinetic and thermodynamic compensations were concluded to be real and the extraction process was controlled by entropy. A total of ten phenolic compounds including six phenolic acids (tannic acid, gallic acid, ellagic acid, caffeic acid, ferulic acid and p-coumaric acid) and four flavonoids (catechin, epicatechin, quercetin and myricetin 3-O-rhamnoside) were identified and quantified in jamun leaf extract obtained under optimum extraction conditions. The selection of appropriate membrane in the microfiltration step was a critical aspect. To observe the effect of membrane pore size on the permeate flux and permeate quality, leaf extracts were then micro-filtered using four different microfiltration membranes (0.1, 0.22, 0.45, and 0.8 mu m) under batch concentration mode. The flux decline was successfully described by the Hermia's cake filtration model. The stability of clarified extract was investigated at 4 degrees C for 45 days. The 0.45 mu m microfiltration membrane was suggested for the clarification of jamun leaf extract in order to achieve high flux, polyphenol recovery, extract purity and improved storage stability.