Possibility of quinine transformation in food products: LC–MS and NMR techniques in analysis of quinine derivatives

Abstract

Quinine is an alkaloid consisting of two major systems: quinoline and quinuclidine. It receives the attention of scientists because of its several medical properties: antimalarial, painkilling and fever-reducing properties. Moreover, it is widely used in food industry as a flavor component. Although the method of quinine synthesis is known, the most cost-effective is its isolation from its natural source, the bark of Cinchona tree. Liquid–solid extraction is the predominantly applied method for the isolation of active biological compounds from different plants. We found that the heating of the quinine in phosphoric buffer solution with low pH produced at least five compounds, whereas the heating of the quinine in alcohol/phosphoric buffer solution with decreased pH produced at least eight compounds. The formation of hydroxy and alkoxy adducts has not yet been reported. We observed that the amount of each formed component is dependent on the heating time, alcohol concentration in alcoholic/buffer mixture and pH. The presented results are particularly important in the context of the use of quinine as food ingredient, because quinine derivatives, quinine structural isomers and their derivatives can be formed in significant amounts and their influence on the human body has not been fully explored yet.