title: Evaluation of antioxidant and xanthine oxidase inhibitory activity of different solvent extracts of leaves of Citrullus colocynthis.
abstract: BACKGROUND
  Citrullus colocynthis is a folk medicinal plan of United Arab Emirates. Several studies on this plant reported and focused on the biological and toxicological profile of fruits pulp. The present study focused on the antioxidant potency of leaf extract of this plant.
  
  
  OBJECTIVE
  To evaluate the antioxidant and xanthine oxidase (XO) inhibitory activities of C. colocynthis by chemical method.
  
  
  METHODS
  Four different solvent extracts (methanol-CCM, methanol: water (1:1)-CCMW, chloroform-CCC and hexane-CCH) of leaves of C. colocynthis were investigated for their free radical scavenging activity using DPPH radical as a substrate, lipid peroxidation (LPO) inhibitory activity using a model system consisting of β-carotene-linoleic acid, superoxide radical scavenging activity (enzymatically/nonenzymatically) and XO inhibitory activity. A dose response curve was plotted for determining SC50 and IC50 values for expressing the results of free radical scavenging activity and XO inhibitory activities respectively.
  
  
  RESULTS
  The high polyphenolic content of CCM and CCMW extract showed highest antioxidant activity irrespective the method used for this investigation. The overall results decreased in the order of: CCM > CCMW > CCC > CCH. CCH extract was inactive towards chemically generated superoxide radical and poor DPPH radical scavengers. The results of LPO inhibitory activities of leaves extract (0.1, 0.5 and 1.0 mg/mL) also decreased in the order of: CCM > CCMW > CCC > CCH. Overall 1.0 mg/mL leaves extract showed highest antioxidant potency amongst the studied concentration.
  
  
  CONCLUSIONS
  CCMW and CCM extract of C. colocynthis exhibited promising antioxidants and XO inhibitory activities.
authors.affiliation: Department of Pharmaceutical Chemistry and Natural Products, Dubai Pharmacy College, Dubai, United Arab Emirates.
authors.forename: Fazilatun
authors.initials: F
authors.lastname: Nessa
authors.affiliation: Department of Pharmaceutical Chemistry and Natural Products, Dubai Pharmacy College, Dubai, United Arab Emirates.
authors.forename: Saeed A
authors.initials: SA
authors.lastname: Khan
keywords: Citrullus colocynthis; extracts; free radical and lipid peroxidation; superoxide radical; xanthine oxidase