Bioactive polyphenolic compounds and antioxidant potentials of two leafy vegetables in Bangladesh: the Momordica charantia and the Ipomoea aquatica

Abstract Momordica charantia and Ipomoea aquatica leaves are two green leafy vegetables in Bangladesh that are commonly consumed considering their characteristic taste and abundant availability in nature. The aim of this study was to determine the available bioactive phenolic constituents as well as total flavonoid content (TFC), tannin content (TTC), phenolic content (TPC), antioxidant activity (TAA) and DPPH radical scavenging activity (IC50) of the ethanolic extracts of M. charantia (MCE) and I. aquatica (IAE). HPLC–DAD and UV–visible spectrophotometer were used to determine the phenolic compounds and antioxidant properties, respectively. In this study, TFC, TTC, TPC, TAA and IC50 values were in the order of IAE (40.73 ± 1.0 mg QE/g) > MCE (34.60 ± 0.46 mg QE/g); MCE (40.93 ± 0.70 mg TAE/g) > IAE (31.13 ± 0.42 mg TAE/g); MCE (27.76 ± 0.58 mg GAE/g) > IAE (21.29 ± 0.43 mg GAE/g); MCE (52.03 ± 0.21 mg AAE/g) > IAE (40.77 ± 0.15 mg AAE/g) and MCE (333.22 ± 67.37 µg/mL) > IAE (560.74 ± 10.25 µg/mL). M. charantia ethanolic extracts contained five hydroxycinnamic acid: ferulic acid, chlorogenic acid, p-coumaric acid, rosmarinic acid and cinnamic acid; five flavonoids: epicatechin, quercetin, catechin, rutin hydrate and myricetin; two hydroxybenzoic acid: gallic acid and vanillic acid; and one phenolic aldehyde: vanillin. Whereas, I. aquatica extracts possessed four hydroxycinnamic acid: chlorogenic acid, p-coumaric acid, trans-ferulic acid and trans-cinnamic acid; four flavonoids: epicatechin, quercetin, catechin, and rutin hydrate; two hydroxybenzoic acid: gallic acid and vanillic acid; and one phenolic aldehyde:vanillin. These underutilised sources of leafy vegetables may be used to develop functional foods by emphasising their remarkable bioactive components. Graphical Abstract