(732g) Recovery of Bioactive Catechins From Aqueous Extract of Tea Leaves (Camellia sinensis) By Liquid Membrane (LM) Technique Leading to the Formation of Metal-Catechin Complex

Catechin compounds aid great pharmacological benefits to human health such as reduction of cholesterol and hypertension, anti-oxidation, anti-microbial, protection against cardiovascular disease and cancer (Ghoshal et al, 2012). They are found in leaves and flowers of tea plants (Camellia sinensis). Recovery of these bioactive components from hot (60¢ªC) water extract of tea leaves using liquid membrane based separation has been studied in the present work. Liquid membrane technology is an advancement of the conventional solvent extraction process with the best advantage of simultaneous extraction and stripping of the target solute along with other advantages such as very low consumption of extractant, lower energy consumption, low installation cost etc. Liquid membrane, in general is a thin liquid film interposed between two other phases of different composition, viz. feed phase and strip phase (both immiscible with membrane phase). The target solute is extracted in the feed side interfaces and diffuses through the liquid membrane due to concentration gradient and as soon as it reaches to the strip side interface, it is stripped by the stripping agent due to its higher affinity to the solute. Tributyl phosphate (TBP), a neutral carrier in n-decane is identified as the most efficient solvent-carrier combination (membrane phase) in two phase equilibrium study (Manna et al., 2012). On the other hand, metals play an important role in medical science with their biological activity as complexing agent, in addition to the fact that they are essential in human diet chart. Metal-catechin complex (Mhatre et al., 1993) is important species for some biological functions like gene expression, apoptosis, enzyme regulation and neurotransmission. Various transition metals such as Cu²⁺, Zn^2+, Co^2+, Fe^2+, Mg²⁺, Ca²⁺ as well as Al²⁺ and Al³⁺  (in their respective aqueous salts) were tried as striping agent and also for formation of complexing agent. AlCl₃ was found as the best stripping as well as catechins complexing agent due its larger standard reduction potential. The metal (Al⁺³) complexation with various catechin compounds were confirmed through the change of UV-vis. spectrum of the bioactive compounds. Al-catechin complex was found as 2:1 in elementary analysis in excess (molar basis with respect to catechins in stripping phase) AlCl₃ in stripping phase. The complex formation was confirmed also by FT-IR and X-ray diffraction analyses. 60% extraction and 48% recovery of the catechin have been achieved at the optimum conditions of the operating parameters viz.12% (v/v) TBP in the membrane phase, 100 mg L^-1 (0.00034 M) feed phase concentration, pH 4.0, 0.02 M AlCl₃ as stripping agent and stirring speed of 400 rpm of both the feed and receiving phases.

Literature cited

1. Manna M.S., Bhatluri K.K., P. Saha and A.K. Ghoshal (2013). “Transportation of catechin (±C) using physiologically benign vegetable oil as liquid membrane”, Industrial & Engineering Chemistry Research, in press, DOI: 10.1021/ie3017863.

2. Ghoshal, A. K.; P. Saha; Manna, M. S.; Bhatluri, K. K. (2012) “Environmentally Benign Liquid  membrane Technology for Chemical, Pharmaceutical and Medicinal Applications”, presented in 2nd Indo-German workshop on “Advances in Reaction and Separation Process” , 20-22 Feb 2012, Bad Herrenalb, Germany.

3. Mhatre, S. N., Iyer, R. K., Moorthy, P. N., 1993. Characterization of aluminium complexes in tea extract. Part I-Al NMR studies, Magnetic Resonance in Chemistry, 31(2), 169-175