Desenvolvimento de método eletroanalítico por voltametria de pulso diferencial para determinação de Flavan-3-ol em fitoterápicos

Abstract

Specialized metabolites are produced by plants that, in addition to being important in their interaction with the environment, can also have different biological activities. Herbal medicines are an example of products that are produced from vegetable raw material and are used as medicine. Quality control is one of the major problems of herbal medicines, as several factors can change the quality of vegetal material, such as the concentration of bioactive compounds. Thus, the development of low-cost, portable, and fast analytical methods that assist in quality control becomes interesting. This work aimed to develop an electroanalytical method, using differential pulse voltammetry (DPV), for the quantification of flavan-3-ols in herbal medicines with the aid of metallic complexation. Chelation of flavonoids with AlCl3 allows us to differentiate some flavonoid classes from the class of flavan-3-ol. The proposed quantification presented good results of recovery (95.9 ± 1%), linearity (R2 = 0.9978), precision, selectivity, and low limits of detection (2.09 μmol L-1), and quantification (6.95 μmol L-1). Then, the quantification of flavan-3-ol in herbal medicines (CV1-5) was performed, which indicated concentrations of catechin equivalent of 1.23 to 470.43 mg per gram of herbal medicine, while the comparative method that determines the total phenol content presented concentrations of gallic acid equivalent from 17.89 to 513.83 mg per gram of herbal medicine. However, comparing the herbal medicines CV3 and CV4, CV3 had lower flavan-3-ol content, but its total phenol content is higher. Thus, the content of total phenols proves to be inefficient in the use of monitoring the content of flavan-3-ol. The analysis by mass spectrometry of green tea medicines identified the presence of the flavan-3-ol class, proving the presence of these compounds in the samples. The result indicates that the developed method is more selective for a certain class of flavonoids and is promising for use in the quality control of herbal medicines that present flavan-3-ols as bioactive compounds.