Antioxidant activity of Geranium robertianum concentrated extracts by ultrafiltration process

This paper describes the efficiency the integrated membrane process for obtain of concentrated medicinal plant extract as alternative to the traditional vacuum evaporation. The attention focused on the vegetal extracts obtained from Geranium robertianum L., herb Robert (Geraniaceae) is justified by their use in the traditional medicine for the treatment of human and animal diseases [1]. Geranium robertianum concentrated extract by ultrafiltration process was examined for antioxidant properties. The antioxidant capacities and total polyphenols contents of the extracts were evaluated using ABTS and DPPH scavenging methods [2,3] and the total polyphenolic content was determined using the Folin-Ciocalteu method [4]. The air-dried ground aerial parts of the Geranium robertianum were extracted with two solvents: distilled water (8% w/v). After filtration, the extract was processed by microfiltration (MF) through Millipore membrane with 0.45µm pores, followed by concentration using the ultrafiltration process (UF). The ultrafiltration process was performed using two types of membranes with a cut-off 10,000Da: UF1 with cellulose regenerated membrane and UF2 with polysuphone membrane. The results show that even low molecular mass compounds like polyphenols pass through membranes, the content of polyphenols in retentate (4.22mg/L – UF1 and 4.68mg/L – UF2) was higher than all the permeates (3.15mg/L – UF1 and 3.52mg/L – UF2). The data were sustained by TEAC values obtained for retentates (1247.3µmol Trolox equivalent – UF1 and 2634.4µmol Trolox equivalent – UF2) and permeates (711.4µmol Trolox equivalent – UF1 and 1372.5µmol Trolox equivalent – UF2). The values obtained by the DPPH assay varied from 77.6% DPPH inhibition for the G.robertianum aqueous extract to 95.3% DPPH inhibition for the UF1 concentrated extract and 92.5% DPPH inhibition for the UF1 concentrated extract. The results of this study show the performance of ultrafiltration membranes for the medicinal plants concentration and that the aqueous of Geranium robertianum extracts have a high antioxidant activity and can be considered as good source for further medicinal applications.

Acknowledgements: This work was financially supported by the Romanian National Center for Program Management – PN62076/2008 and PN71025/2007.

References: [1] Chevallier, A. (1996) The Encyclopedia of Medicinal Plants, Dorling Kindersley Limited, London.

[2] Rice-Evans, C., Miller, N.J. (1994) Meth. Enzymol. 234:279–293.

[3] Litescu, S., Radu, G.L. (2000) Eur. Food Res. Technol. 211(3):218–221.

[4] Waterhouse, A.L. (2002) Current Protocols in Food Analytical Chemistry. John Wiley&Sons. New York.