Potential antioxidant phenolic metabolites from doum palm leaves

ABSTRACT

The antioxidant activity of the aqueous ethanolic extract of doum leaves, Hyphaene thebaica L.(Palmae) was studied. Data obtained showed that the extract can inhibit reactive oxygen species attack on salicylic acid (IC50 = 1602 µg/ml) in a dose dependant manner using xanthine/hypoxanthine oxidase assay. Four major flavonoidal compounds were identified by LC/SEI as; Quercetin glucoside, Kaempferol rhamnoglucoside and Dimethyoxyquercetin rhamnoglucoside. While, further in-depth phytochemical investigation of this extract lead to the isolation and identification of fourteen compounds; their structures were elucidated based upon the interpretation of their spectral data (UV, 1H, 13C NMR and ESI/MS) as; 8-C--D-glucopyranosyl-5, 7, 4`-trihydroxyflavone (vitexin) 1, 6-C--D-glucopyranosyl-5, 7, 4`-trihydroxyflavone (iso-vitexin) 2, quercetin 3-O--4C1-D-glucopyranoside 3, gallic acid 4, quercetin 7-O--4C1-D-glucoside 5, luteolin 7-O--4C1-D-glucoside 6, tricin 5 O--4C1-D-glucoside 7, 7, 3` dimethoxy quercetin 3-O-[6''-O--L-rhamnopyranosyl]--D-gluco-pyranoside (Rhamnazin 3-O-rutinoside) 8 kaempferol-3-O-[6''-O--L-rhamnopyranosyl]--D-glucopyranoside (nicotiflorin) 9, apigenin 10, luteolin 11, tricin 12, quercetin 13 and kaempferol 14