Effective Utilization of Citrus unshiu Plant Waste Extracts with Lipase Inhibitory Activities

During the course of Citrus unshiu fruit cultivation, large amounts of plant material including pruned leaves, thinned-out flowers and unripe fruit are obtained; these materials are generally considered unusable and discarded as plant wastes. We have previously attempted to establish an effective use of such plant wastes as beneficial natural resources and found that a methanolic extract of pruned Citrus leaves (CUL-ext) exhibited inhibitory activity against porcine pancreatic lipase. In this study, we sought to identify further the effective uses of C. unshiu plant wastes by determining the lipase inhibitory activity of methanolic extracts of thinning out flowers (CUF-ext) and unripe fruit (CUUF-ext). We accordingly found that the inhibitory activity of CUF-ext was superior to that of CUUF-ext and comparable to that previously observed using CUL-ext. Fractionation of CUF-ext and CUUF-ext, followed by chromatographic analyses, revealed that the pancreatic lipase inhibitory activities of these extracts could be attributed, at least in part, to the flavonoids hesperidin, nobiletin, narirutin and rutin. On the basis of present findings, we propose that, in addition to pruned Citrus leaves, the thinned-out flowers and unripe fruit of C. unshiu are natural resources which are suitable for preparing constituents with lipase inhibitory activity.