Taxifolina: quantificação do flavonoide no extrato seco da casca de Pinus pinaster e avaliação da liberação in vitro e permeação vaginal ex vivo

Abstract

The dry extract obtained from the bark of the Pinus pinaster, popularly known as French Maritime Pine, has a high concentration of polyphenols represented by procyanidins, taxifolin, phenolic and cinnamic acids and glycosylated forms of these molecules. It is obtained by aqueous extraction of the pine bark, followed by water removal. Its quality control is specified in the United States Pharmacopeia, and the assay test is performed by determining of the total procyanidins content (between 65 and 75 %). However, determining of the individual polyphenol content may represent an additional quality parameter for this extract. In this sense, the taxifolin (flavonoid known as dihydroquercetin) appears as a possible chemical marker for assay, since it is found in the genus Pinus, in general, and because it represents the monomeric polyphenol in the highest concentration. This molecule possesses antioxidant and anti-inflammatory properties and may be used in the treatment of diseases which have oxidative stress and inflammation involved in the pathogenesis. Endometriosis is the main focus of this current study, whose pharmacological treatment is performed with contraceptives mainly, and presents a widely range of disadvantages, such as the high degree of adverse effects; recurrence of symptoms a few months after discontinuation of treatment, in most cases; and contraception, which prevents that the patient to become pregnant. These factors encourage the search for new drugs to treat endometriosis. However, despite of the pharmacological potential of taxifolin, it shows low oral bioavailability due to poor water solubility, which limits its therapeutic application and encourages the search for alternative routes of administration for this flavonoid. Within this context, the present study has like aims: (i) to develop and validate analytical methods by high performance liquid chromatography for quantification of taxifolin in the extract and vaginal cream and (ii) to evaluate the in vitro release profile of taxifolin from the cream and its ex vivo permeation across porcine vaginal mucosa. The analytical methods developed and optimized for the quantification of taxifolin in the extract and vaginal cream employed reversed phase chromatography with octadecylsilane stationary phase and mobile phase composed by water, acetonitrile and formic acid in different proportions to the methods. It was used gradient elution (mobile phase composition and flow rate) in the extract method, and isocratic elution in the cream method. The detection was performed at 288 nm in photodiode array detector. The chromatographic profiles showed regular baselines, appropriate resolution of taxifolin, and good symmetry of the peak. All analytical validation parameters were within specifications. The in vitro drug release study showed that the cream is a possible vehicle for vaginal administration of taxifolin due to high release rate (74.89 µg cm−2 h−1). Additionally, the permeated percentage of taxifolin by dose (89.22 %) suggests a potential of this flavonoid to exercise its systemic effects in vivo when administered via vaginal route, and may be an alternative for the treatment of endometriosis, emphasizing that it has no contraceptive effect.