Purification of papain by metal affinity partitioning in aqueous two-phase polyethylene glycol/sodium sulfate systems.

A simple and inexpensive aqueous two-phase affinity partitioning system using metal ligands was introduced to improve the selectivity of commercial papain extraction. Polyethylene glycol 4000 was first activated using epichlorohydrin, then it was covalently linked to iminodiacetic acid. Finally, the specific metal ligand Cu(2+) was attached to the polyethylene glycol-iminodiacetic acid. The chelated Cu(2+) content was measured by atomic absorption spectrometry as 0.88 mol/mol (polyethylene glycol). The effects on the purification at different conditions, including polyethylene glycol molecular weight (2000, 4000, and 6000), concentration of phase-forming components (polyethylene glycol 12-20% w/w and sodium sulfate 12-20%, w/w), metal ligand type, and concentration, system pH and the commercial papain loading on papain extraction, were systematically studied. Under optimum conditions of the system, i.e. 18% w/w sodium sulfate, 18% w/w polyethylene glycol 4000, 1% w/w polyethylene glycol-iminodiacetic acid-Cu(2+) and pH 7, a maximum yield of 90.3% and a degree of purification of 3.6-fold were obtained. Compared to aqueous two phase extraction without ligands, affinity partitioning was found to be an effective technique for the purification of commercial papain with higher extraction efficiency and degree of purification.

Optimization of extraction conditions of areca seed polyphenols and evaluation of their antioxidant activities.

Polyphenols are functional compounds in plants, which possess many bioactivities beneficial for humans. The aim of this study was to establish a highly efficient method for extracting polyphenol compounds from areca seeds and further to identify polyphenols and antioxidant properties of the seeds. A quadratic general rotary unitized design was used to determine the optimal extraction process. The polyphenols were identified using LC-TOF-MS. By comparison with ascorbic acid (Vc), the antioxidant activities of the ethanol extracts were evaluated using three complementary in vitro assays: inhibition of the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging activity, hydroxyl radical-scavenging activity, and reducing ability. The two major polyphenols obtained were epicatechin and syringic acid. The ethanol extracts of areca seeds showed significantly greater antioxidant activity (p < 0.05) than Vc using the DPPH and reducing power assay, but lower ability (p < 0.05) using the hydroxyl radical assay. The results indicate that the areca seed is an excellent food material with potential antioxidant properties.