Isolation and characterisation of novel antioxidant constituents of Croton zambesicus leaf extract

Abstract

A 1,1-diphenyl-2-picrylhydrazyl (DPPH)-activity-directed fractionation was used to target antioxidant constituents of the ethyl acetate fraction obtained from a 20% aqueous methanol crude extract of Croton zambesicus leaf. Repeated column chromatography of the fraction on silica gel and Sephadex LH-20 led to the isolation of a new natural product, identified as quercetin-3-O-β-6″(p-coumaroyl) glucopyranoside-3'-methyl ether, helichrysoside-3'-methyl ether (1), along with kaempferol-3-O-β-6″(p-coumaroyl) glucopyranoside, tiliroside (2) and apigenin-6-C-glucoside, isovitexin (3) as the antioxidant constituents. The structures of the isolated compounds were elucidated using spectroscopic techniques, namely NMR (1D and 2D) and mass spectrometry. Compounds 1 and 2 are reported from this species for the first time. In the qualitative antioxidant assay, the three isolated compounds instantly bleached the DPPH (0.2% MeOH) purple colour indicating antioxidant activity. In the quantitative antioxidant assay, all the isolated compounds demonstrated weak antioxidant activity compared to quercetin and rutin used as positive control antioxidant agents. The compounds displayed little to no cytotoxicity against Vero cells in an in vitro assay. The presence of these antioxidant compounds in the leaf extract of C. zambesicus could provide a rationale for the ethnomedicinal use of the plant in the management of oxidative-stress-related diseases in folk medicine.

A Review on the Dietary Flavonoid Tiliroside

“…The IC 50 value for tiliroside in DPPH assays varied from 6 to 606 μM. For superoxide radical scavenging, the IC 50 varied from 21.3 to 119.95 μM, with one observation of IC 50 in a concentration higher than tested (500 μM) (Aderogba, McGaw, Bezabih, & Abegaz, ; Da Silva, Souza, Da Silva, Lemos, & Conserva, ; de Oliveira et al., ; Devi & Kumar, ; Ding, ; Indrianingsih, Tachibana, Dewi, & Itoh, ; Ishaque, BiBi, Valant‐Vetschera, Schinnerl, & Bacher, ; Kancheva, Dinchev, Tsimidou, Kostova, & Nenadis, ; Mekhelfi et al., ; Ndhlala, Aderogba, Ncube, & Van Staden, ; Park et al., ; Pei et al., ; Rao, Geethangili, Fang, & Tzeng, ; Sala et al., ). Other models include the following: (1) FRAP, whose antioxidant activity was expressed as Trolox equivalents (TE), equal to 28.37‐ μmol TE/g of extract (Mekhelfi et al., ); (2) xanthine/xanthine oxidase assays in which IC 50 did not reach the maximal tested concentration of 50 μM (Park et al., ); (3) relative assays such as linolenic acid oxidation in comparison to α‐tocopherol (7.2%) (Sala et al., ) and the ability to prevent beta‐carotene bleaching, reaching approximately 40 mg/g gallic acid equivalent and 80 mg/g quercetin equivalent (Indrianingsih et al., ); (4) LDL oxidation assays, showing that a concentration of tiliroside equal to 10 μM completely stopped oxidation (Schinella et al., ); and (5) the oxidation rate ratio, calculated as equal to 0.06 (Ndhlala et al., ).…”

Biological screening of extracts from leaf and stem bark of Croton floribundus Spreng. (Euphorbiaceae)

“…This is the first report of the antioxidant activity of C. floribundus. Other species of Croton have been related to possessing an antioxidant activity (Aderogba et al, 2011;Donati et al, 2015;Shahwar et al, 2015). The popular use of these Croton species is enhanced by the verification of its antioxidant action (Morais et al, 2006).…”

The Pavonia xanthogloea (Ekman, Malvaceae): Phenolic compounds quantification, anti-oxidant and cytotoxic effect on human lymphocytes cells

“…Tiliroside is a glycoside flavonoid [kaempferol 3-O-(6′′-trans-p-coumaroyl)-β-D-glucopyranoside] and is present in several medicinal and dietary plants, such as rose hip, strawberry and linden. [ 20 21 22 ] Despite to be less studied than other polyphenols as catechin and quercetin, previous investigations of tiliroside biological activity have described anti-oxidant activity[ 23 24 25 ] as well as other biological properties including described anti-inflammatory, anticarcinogenic and anti-obesogenic tiliroside effects. [ 22 23 26 27 ] The n-butanol fraction also presented anti-oxidant activity probably due higher quercitrin concentration, a glycosylated form of quercetin.…”