## 2 Materials and Methods
### Determination of Tannin Content  
In order to assess the tannin content of _Q. robur_ oak and _Q. infectoria_ oak, an analytical methodology with hide powder was used, reflecting the pharmacological properties of the raw material, i.e., binding to and precipitating protein. This protein is hide powder, specifically, ground pure collagen. The research methodology consists of determining the percentage content of tannins by calculating the difference between Total polyphenols and Polyphenols not adsorbed by the hide powder while referring to the standard, i.e., pyrogallol solution. This methodology uses the reaction of polyphenols with phosphoriodynobutomstic reagent in which, in the sodium carbonate environment, after 30 min of incubation, blue reaction products are formed. The intensity of the blue color of the solution is proportional to the polyphenol content and is tested with a spectrophotometer by measuring the absorbance at 760 nm, using water as the compensation liquid. Due to the instability of tannins in aqueous solutions, all the extraction and dilution operations must be protected from light. This methodology is recommended by the latest \"European Pharmacopoeia 10\" [32] and was previously used in our earlier works [15; 16]. The research used a 356P water bath (Unipan, Warsaw, Poland), MST magnetic stirrer (Velp Scientifica, Usmate Velate, Italy), analytical and semi-analytical balances (AS110.R2 Radwag, Radom, Poland, Vibra DJ-150S Shinko Denshi, Vibra SJP Shinko Denshi, Tokyo, Japan) and a Vis 5100 spectrophotometer (Metash, Shanghai, China). The following reagents were used: pyrogallol (Sigma, Aldrich, St. Louis, MO, USA), hide powder (EDQM, Strasbourg, France), sodium carbonate (Stanlab, Lublin, Poland), 0.45 \(\upmu\)m syringe filters (Whatman and Merck, Darmstadt, Germany) and purified water with a conductivity below 0.05 \(\upmu\)S/cm (Basic 5, Hydrolab, Straszyn, Poland). The obtained results were expressed in accordance with the pharmacopoeial recommendation as a pyrogallol.  
Both the chromatographic profiles and the ion mass distributions of the _A. infectorius_ and _C. quercetin_ gall nuts were obtained by using the high-performance liquid chromatography (HPLC) technique coupled with two types of detection: spectrophotometry using a photodiode array detector (DAD) (Agilent Technologies 1200 Series, Waldbronn, Germany) and mass spectrometry (triple quadrupole MS, 6470 Agilent Technologies Waldbronn, Germany). The obtained chromatograms were recorded at a wavelength of 276 nm. Ion mass distribution spectra were obtained in the SCAN mode of MS operation. Detailed operating parameters of the chromatographic system are presented in Table 1.  
The study was preceded by the preparation of standard solutions of gallic acid and tannic acid--tannins (Sigma-Aldrich, St. Louis, MO, USA), consisting of dissolving certified standards of both substances in water and obtaining solutions with a concentration of 2 and 9 mg/mL, respectively. Real samples were prepared by suspending about 20-30 mg of powdered real samples in 50 mL of deionized water, followed by a half-an-hour extraction in a boiling water bath. The obtained extracts were analyzed with HPLC-DAD-MS.