Abstract
A systematic study was carried out on the antioxidants in miracle fruit leaf extract. The total phenols, total flavonoids, saponins and the antioxidant activities of the extract were evaluated using the 2,2′-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis-3-ethyl-benzotiazolin-6-sulfonic acid (ABTS), metal chelating capacity (MCC) and ferric reducing antioxidant power (FRAP) assays. The results showed that the leaves contained high phenol concentrations of 90.0 ± 4.78 mg gallic acid equivalent/g dry weight, total flavonoids at 33.0 ± 1.92 mg rutin equivalent/g dry weight, and saponins at 27.8 ± 1.64 mg oleanolic acid equivalent/g dry weight. The extract possessed excellent free radical scavenging ability and high antioxidant capacities. Furthermore, eighteen polyphenol and flavonoid constituents in the extract were identified by using ultra-high performance liquid chromatography-diode array detector-tandem mass spectrometry (UPLC-DAD-MSn) method and standard chemicals. The constituents were gallic acid, 5-O-caffeoylquinic acid, 3-O-p-coumaroylquinic acid, 5-O-p-coumaroylquinic acid, 3-O-feruloylquinic acid, 4-O-caffeoylquinic acid, 4-O-p-coumaroylquinic acid dimer, 4-O-p-coumaroylquinic acid, 4-O-feruloylquinic acid, 4-O-feruloylquinic acid, rutin, myricetin-3-O-rhamnoside, quercetin-3-D-galactoside, quercetin-3-glucoside, kaempferol-3-O-glucoside, quercetin-3-rhamnoside, myricetin-O-galloylrhamnoside and quercetin-3-O-(2′′-galloyl)-rhamnoside.Eight constituents were quantified with values from 0.12 to 4.13 mg·g‒1. The extract of miracle fruit leaves was also used in an anti-Alzheimer's disease model for potential medical applications. The assay indicated that the extract provided apparent inhibition for the paralysis of Caenorhabditis elegans at a concentration of 0.02 mg·mL‒1. This work demonstrated that miracle fruit leaves are rich in bioactive antioxidants with potential for drug and functional product development.
Disclosure statement
The authors declare that they have no conflicts of interest.