Chemical structure and properties of anthocyanins from selected plant species from Uganda towards nutraceutical development

Abstract

Noncommunicable diseases pose national and global threat to public health and hence there is a need for appropriate intervention. Ingestion of nutraceuticals rich in anthocyanin phytochemicals is associated with reduced risk of noncommunicable diseases. However, sources of anthocyanins with appropriate qualities for nutraceutical development are limited. Therefore, in this study the chemical structure and properties of anthocyanins from plants were investigated with a view of identifying anthocyanins suitable for application as nutraceutical ingredients, functional foods and natural food colourants. Anthocyanins from the leaves of Hemigraphis colorata (Blume) H. G. Hallier, flowers of Erlangea tomentosa (Oliv. & Hiern) S. Moore, flowers of Cordyline terminalis (Kunth), leaves of Dissotis brazzae Cogn. and fruits of Cyphostemma adenocaule (Wild and Drumm) were isolated and analysed by a combination of methods which included maceration, solvent partition, chromatographic and spectroscopic techniques, chemical analysis and DPPH radical scavenging. The isolated and identified compounds included 3-O-methylated anthocyanidin (erlangidin) derivatives from E. tomentosa, 5-O-methylated anthocyanidin derivatives from H. colorata, dietary acylated delphinidin and cyanidin anthocyanins from C. adenocaule which were novel compounds. Others were cyanidin 3, 5-O-β-diglucopyranoside, peonidin 3, 5-O-β-diglucopyranoside, acylated cyanidin derivatives, acylated peonidin derivative from C. terminalis, cyanidin 3-O-β-glucopyranoside, and cyanidin 3-O-α-rhamnopyranoside from D. brazzae, which are known compounds. The novel compounds exhibited some unique and desirable properties with regard to stability and equilibrium transformations. The compounds showed remarkable antioxidant activity (IC50: 11.1 ± 0.8 to 36.4 ± 0.5 μg/ml) which is indicative of their potential beneficial health effects. Therefore, in this study anthocyanins with nutraceutical, functional food and colourant potential were identified from new plant sources. C. adenocaule fruits may be considered for commercial exploitation due to a high amount (7.88± 0.32 mg/g fr. wt) of highly acylated dietary anthocyanins.