Chromatographic analysis of phenolic acids from Iris species. Comparison of different methods of extraction

Phenolic acids have been reported to possess important biological and pharmacological properties, especially antioxidant activity, which have been widely described in the literature.

The aim of this study was the quantification of phenolic acids in extracts obtained with different extraction techniques from several Iris species. A pressurized liquid extraction (PLE) was performed in an ASE 100 accelerated solvent extractor (Dionex, USA) at 100°C using 80% and 100% methanol. To compare the effectiveness of PLE, the ultrasound-assisted extraction (UAE) procedure was also carried out, as well as traditional Soxhlet extraction (SX). To purify the PLE, UAE, SX extracts, the well-known solid phase extraction (SPE) technique was applied. Next, SPE eluates were qualitatively and quantitatively analyzed using an Agilent 1100 liquid chromatograph with UV-visible diode-array detector (DAD). As the result of the study, seven phenolic acids were identified by SPE-RP-HPLC: vanillic, caffeic, chlorogenic, protocatechuic, ferulic, p-coumaric and gallic acids. The calibration curves for all standards were linear (R²>0.999, n=3) in a concentration range of 0.01–2.00mg 10ml^-1. For most acids (vanillic, protocatechuic, p-coumaric, gallic, ferulic) isolated from the investigated Iris species, the highest yield was achieved by ASE at 100°C repeated three times with 80% methanol as a solvent, while the worst results were obtained by ultrasound-assisted extraction (UAE). A relatively high yield of caffeic acid was also obtained with a Soxhlet apparatus (11.10mg/100g dry wt. in aerial parts of Iris bungei Maxim.).

Acknowledgments: This work was financially supported by grant no N N 405 374835 from The Polish Ministry of Science and Higher Education.