Desenvolvimento e validação de métodos analíticos para o controle de qualidade de formas farmacêuticas contendo chá verde (Camellia sinensis) e estudos de liberação e permeação cutânea

Abstract

Currently, there is an increased interest in potential health-protective activities of green tea (Camellia sinensis), which is characterized by the presence of polyphenols huge amounts, being the majority of them catechins. Epigallocatechin 3- gallate (EGCG) is the most abundant and active component, been generally used as biomarker together with caffeine (CAF) and gallic acid (GA). EGCG is poorly absorbed in the gastrointestinal tract and is subject to first-pass metabolism by the liver when administered orally, the most widely used forms of green tea. A transdermal system could then be an alternative delivery mechanism. In this light, the present work aimed: to develop and validate high performance liquid chromatography (HPLC) methods for simultaneous quantification of EGCG, CAF and GA in emulsions and capsules containing dry extract green tea and to determine in emulsion the in vitro EGCG release and its human skin cutaneous permeation using ex vivo model. The methods used reversed phase HPLC and photodiode array detection. Separation was achieved using the follow conditions: octadecylsilyl column; mobile phase composed by water, ethanol, ethyl acetate and acetic acid (84:12:3:1, v/v/v/v); column temperature of 35 °C; and flow gradient syst em, alternating flow between 0.7 and 1.4 mL.min-1. The compounds were separated within 35 min. The methods were simple, selective, precise, accurate and fast; and provide the reliability required for them to be used for quality control of tested formulations. The emulsion method proved to be suitable both for in vitro release and ex vivo permeation. EGCG in vitro release rate was found to be 8896.01 μg.cm–2, following pseudo-first-order model, also known as Higuchi’s model. Ex vivo permeation testing showed that EGCG is not able to exert its biological activities systemically when used from tested emulsion, remaining only in the stratum corneum.