Abstract
Many natural products of commercial importance in food and pharmaceutical sectors, are complex mixtures of substances. Examples of herbal substances with claimed health benefits include the phenolic compounds. Camellia sinensis (green tea) is a plant with a high concentration of polyphenols with several biological properties such as antioxidant, antitumor, antimicrobial, etc. However, the biological effect can be drastically diminished or lost after oral administration, due to low solubility of the compound in the gastrointestinal tract (low absorption), and the effect of presystemic metabolism. The entrapment of bioactive compounds in liposomes has been proposed as a promising method to overcome bioavailability restrictions. However, depending on the properties of the phenolic substance, a strong physicochemical interaction with the lipid bilayer can emerge, which makes the quantification of the entrapment efficiency difficult. The aim of this work was to develop and validate a HPLC method for quantification of green tea (GT) catechins epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) encapsulated in liposomal lipid carriers. Liquid, spray dried and freeze dried compositions containing lecithin:cholesterol: GT lyophilized extract:surfactant (8:1:2:2) were prepared and used for validation of the HPLC method. Samples were extracted with ultrapure water and with a mixture of water plus triton X-100 (in order to open the lipid vesicles), and analysed using a reversed phase C-18 column. The results were compared with the non encapsulated lyophilized extract of GT and standard substances. A significant change in the HPLC profiles was observed for the encapsulated samples, which was linked to the strong molecular interaction between the GT polyphenols with the phosphatidylcholine lipid bilayers. High encapsulation efficiencies were observed for liquid and dried formulations, which were dependent of the polyphenol moiety (EGCG > ECG).
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