Potentilla erecta (L.) rhizomes as a source of phenolic acids

The aim of this study was to evaluate the content of major phenolic acids from Potentilla erecta rhiozomes. Water and ethanol-water mixture was used for extraction of these compounds. The extracts were also evaluated for the quantification of total phenolic content and the antioxidant capacity. The contents of phenolic acids and resulting antioxidant activities are dependent on the nature of extracting solvent due to the presence of different antioxidant compounds. Results showed that P. erecta rhiozomes contained high amount of gallic and p -HBA acids. The contents of chlorogenic and protocatechuic acids in the extracts of Potentilla species have not been reported yet. The results suggested that the extracts could be used as the active cosmetics ingredients and nutraceuticals.


Plant material and its extraction
The sample of P. erecta rhiozomes was collected during September of 2015 in the east part of Poland (the Podlasie plain). was from 12-years old pine forest (N 52°24', E 23°16'). The voucher specimen was authenticated by Dr Catherina Fyalkowska from Forest Ecology Department and deposited in Forest Research Institute, Poland (No. PEI002015). The collected plant material was dried at 40 o C for 24h, then ground (Pulverisette 15) and sieved (0.5 mm).
The dry plant material (700 mg) was mixed with 25 mL of water or ethanol-water solution (60:40, v/v) for 20 min at room temperature. Then, the extracts were filtered through Whatman No.1filter paper. Three independent extractions using appropriate solvent were carried out.

Chromatographic analysis
Chromatographic analysis was performed using a Shimadzu HPLC system equipment with a binary pump, degasser, autosampler and connected to 3200 QTRAP Mass spectrometer

Determination of total phenolics
Total phenolic content of extracts was assessed by using the Folin-Ciocalteu (FC) phenol reagent (Singleton et al., 1999). 0.1 mL of extract was mixed with 0.1 mL of FC reagent and 0.9 mL of water. After 5 min, 1 mL of 7% (w/v) Na 2 CO 3 and 0.4 mL of water were added.
The extracts were mixed and allowed to stand for 30 min before measuring the absorbance on a spectrophotometer (PerkinElmer, UV-visible Lambada Bio 20) at 765 nm. A mixture of water and reagents was used as a blank. Total phenolic content was expressed in mg of gallic acid (GA) per gram. Each analysis was done in three repetitions.

The scavenging ability on 1,1-diphenyl-2-pirylhydrazyl (DPPH) radicals
The DPPH assay was applied to estimate the radical-scavenging ability of the fruit extracts (Pyrzynska and Pekal, 2013). 0.1 mL of a given extract was mixed with 2.4 mL DPPH solution (9 x 10 -5 M) in methanol . After 30 min absorbance was measured at 539 nm against the blank. Trolox, a vitamin E analogue, solution was used to calibrate the standard curve.
The mean ± SD results of triplicate analyses were expressed in mmol of trolox (TR) per gram of dry sample.

Cupric reducing antioxidant capacity
For assessing cupric reducing ability (CUPRAC), the assay described by Apak et al. (2004) was adapted. 1 mL of CuCl 2 solution (0.01 mol L -1 ) was mixed with 1 mL of neocuproine alcoholic solution (7.5 x 10 -3 mol L -1 ) and 1 mL of 1 mol L -1 CH 3 COONH 4 , followed by adding 0.5 mL of juice sample and 0.6 mL of water. The tube containing sample and reagents was incubated in a water bath at a temperature of 50 o C for 20 min, after which was cooled under running water. Absorbance against the blank reagent was measured at 450 nm. The results were expressed as trolox equivalent (TR) in mmol g -1 .

Statistical analysis
The results were expressed as mean ± standard deviation for at least three independent determinations. Statistical comparison of the means was performed using one-way ANOVA, followed by Turkey's test and differences at p < 0.05 were considered significant.