The effect of solvents on recovery of polyphenols from the pink fuji apple skin
Flavonoids constitute a group of polyphenols widely distributed in plants and are assumed to have beneficial effects on human health when present in food. The phenolic content of apple fruit skin and leaves was determined at the developmental stage of each organ. Phenolic levels decreased on a dry weight basis during the seasonal development of fruits and leaves with respect to their ontogenesis but the single compounds did not behave uniformly. A shift in flavanol pools from monomeric to oligomeric structures during fruit growth indicated the biosynthetic tendency towards the formation of procyanidins at the end of the growing period. A gas chromatography-mass spectrometry (GC-MS) method was developed for the separation and determination of three major flavones: sinensetin (SEN), rutin (RU) and 3'-hydroxy-5, 6, 7, 4'-tetramethoxyflavone (TMF) and rosmarinic acid (RA), a caffeic acid derivative in the pink skin of apple fruit. The GC-MS method was applied for the quantification of SEN, RU, TMF and RA in apple fruit collected from different local markets of Bangladesh during the period of November 2008. Apple fruit skin contains several bioactive phytochemicals including polyphenols such as flavones and phenolic acids. Dehydrated apple skin powder was used to evaluate the recovery of selected flavones and rosmarinic acid using water, methanol, acetone, chloroform, aqueous 50% methanol, and aqueous 70% acetone at 40oC. The retrieved extracts were subjected to qualitative and quantitative GC-MS analysis. Highest amount of sinensetin (SEN) and rutin (RU) was found in the chloroform extract, which was obtained for 4 to 6 hours of extraction at 40oC. Higher proportion of 3'-hydroxy-5, 6,7,4'-tetramethoxyflavone (TMF) was obtained in pure acetone and as well as 70% acetone where the extraction period 4 to 6 hours, respectively. Similar yield of rosmarinic acid (RA) was obtained in aqueous 70% acetone extracts when the periods of extraction were 2, 4, 6 and 8 hours, respectively.
Key words: Quantification, Malus sylvestris, Lipophillic flavones, GC-MS