Increased water solubility of Propolis extract encapsulated in B-cyclodextrin

DOS SANTOS, CRISTINA; PEREYRA GONZALES, ADRIANA; MAZZOBRE, MARÍA FLORENCIA; BUERA, MARÍA DEL PILAR

Cordba

Congreso; V Congreso Internacional de Ciencia y Tecnología de Alimentos (CICYTAC 2014); 2014

Propolis is a natural resinous mixture of insoluble or slightly soluble substances, principally flavonoids and phenolics acids, of particular interest due to its beneficial effects on health. It has been employed extensively since ancient times in folk medicine and numerous other purposes. Cyclodextrins are able to form inclusion complexes with low polar molecules. The β-cyclodextrin (β-CD) is nontoxic, and chemically stable and can be used to stabilize natural hydrophobic compounds in water. Encapsulation in cyclodextrins (CD) emerge as an innovative method to improve propolis compounds solubility.The aim of this study was to determine the optimum experimental conditions for propolis compounds encapsulation in β-CD. In this work, inclusion complexes of propolis (Poplar propolis) and β-CD were prepared and the stability constants of this process were calculated. Sorption isotherms of β-CD and of the complexes were obtained to analyze the physical properties and the stability of the complexes during the storage. The inclusion complexes were prepared by coprecipitation method and freeze-drying, using different propolis/β-CD molar ratios, temperatures and stirring times. Differential scanning calorimeter, infrared spectroscopy and scanning electron microscopy (SEM) were used to confirm complex formation. Phase solubility studies were carried out according to the method described by Higuchi and Connors, using the Folin-Ciccalteau reaction to determine propolis concentration in water. Antioxidant activity was determined by DPPH and by DSC. Propolis extract composition was analized by HPLC. Poplar propolis was rich in polyphenols and terpenes. The aqueous solubility of propolis compounds increased with the presence of the β-CD. The analysis of solubility as a function of β-CD concentration give up to AL-type diagrams where complexes formed were of first order. The relative thermodynamic parameters (ΔH, ΔS and ΔG) of the encapsulation process were calculated. The negative value of the enthalpy change indicates that the inclusion process is exothermic. The relatively small enthalpy change are typical of low energy interactions prevailing in complexes as hydrophobic interactions as van der Waals forces and hydrogen bonds. The negative value of G°25 indicates that the inclusion process in β-CD is spontaneous. The presence of propolis greatly modified the CD sorption curves being the amount of adsorbed water smaller in the combined systems. These results confirm the complex formation at any of the studied molar ratio. Antioxidan effect of propolis was assesed by DSC, the addition of propolis extract increse the oxidation onset temperature of sensitive oils.The limited water solubility of propolis could be overcome by the formation of β-CD inclusion complexes. This would be important to develop aqueous propolis forms to replace the traditional ethanolic preparations, avoiding unpleasant taste, aromatic odour and high ethanol concentration.