Ziziphus oxyphylla and Cedrela serrata are Pakistan flora species with a reported use in jaundice and against liver diseases1, and with antioxidant and DNA protecting properties2, respectively. In the present study a bioassay-guided fractionation procedure was
used to isolate antioxidant constituents from the leaves of Z. oxyphylla and C. serrata. Ethyl acetate fractions showed the higher DPPH scavenging activity and therefore
they were further subjected to purification by flash chromatography. Seven compounds
(1-7) from Z. oxyphylla and five (8-12) from C. serrata were isolated through semi preparative HPLC and were evaluated in various radical
scavenging assays. Compounds 1, 2 (quercetin-3-O-glucoside and 3-O-galactoside in a different ratio), and 8 (kaempferol-3-O-glucoside), with IC50= 5.33, 7.95 and 4.36 µg/mL, respectively, had significant DPPH scavenging activity
compared to quercetin (3.6 µg/mL) (p= 0.05). Similarly, the superoxide and ABTS assays indicated IC50 values ranging from 0.21 to 0.91 mg/mL and 0.17 to 0.32 mg/mL, respectively. All
isolated compounds were identified as flavonoids, more in particular quercetin and
kaempferol glucosides (monoglucosides such as quercetin-3-O-glucoside, quercetin-3-O-galactoside,
quercetin-3-O-rhamnoside, kaempferol-3-O-glucoside, kaempferol-3-O-galactoside, and
diglucosides). Furthermore, these compounds were potent inhibitors of the formation
of advanced glycation end products (AGEs) in a protein glycation assay. Most of the
compounds had low IC50 values for AGEs inhibition, ranging from 0.53 to 0.84 mg/mL, compared to aminoguanidine,
IC50= 0.51 mg/mL, used as positive control.
References:
[1] Shah SR et al., 2006. Pak Journal of Weed Science Research. 12, 199 – 211.
[2] Perveen F et al., M., 2012. Journal of Natural Products India 5, 207 – 213.
