title: Identification and quantification of phenolic and flavonoid components in straw and seed husk of some rice varieties (Oryza sativa L.) and their antioxidant properties.
abstract: BACKGROUND
  Plant foods are rich sources of bioactive compounds that can act as antioxidants to prevent heart disease, reduce inflammation, reduce the incidence of cancers and diabetes. This study aimed to determine the phenolics and flavonoids profiling in three varieties of rice straw and five varieties of the seed husk of Iranian rice using high-performance liquid chromatography (HPLC). Furthermore, the antioxidant activities of the extracts were evaluated by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and nitric oxide assays.
  
  
  RESULTS
  HPLC analyses showed that the gallic acid, pyrogallol, apigenin and rutin were the main phenolic and flavonoid compounds in all varieties of rice. In addition, the methanolic extracts of Hashemi and Ali Kazemi varieties showed the highest amounts of phenolic and flavonoid contents, respectively. Rice straw and husk of Iranian varieties showed considerable antioxidant activity and Hashemi indicated significantly (P < 0.01) higher DPPH and nitric oxide free radical scavenging activities when compared to the other varieties.
  
  
  CONCLUSIONS
  The present study revealed that rice straw and seed husk of Iranian varieties shows high antioxidant activities and they contain various types of phenolic and flavonoid compounds that could be use in food and medical industries.
authors.affiliation: Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia (UPM), 43400, UPM Serdang, Selangor, Malaysia.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Karimi
authors.forename: Pooyan
authors.initials: P
authors.lastname: Mehrabanjoubani
authors.forename: Maryam
authors.initials: M
authors.lastname: Keshavarzian
authors.forename: Ehsan
authors.initials: E
authors.lastname: Oskoueian
authors.forename: Hawa Z E
authors.initials: HZ
authors.lastname: Jaafar
authors.forename: Ahmad
authors.initials: A
authors.lastname: Abdolzadeh
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000494:pharmacology*; D001713:Biphenyl Compounds; D004032:Diet; D005419:Flavonoids / Q000032:analysis / Q000494:pharmacology*; D006801:Humans; D007492:Iran; D009569:Nitric Oxide / Q000378:metabolism; D012275:Oryza / Q000737:chemistry* / Q000145:classification; D010636:Phenols / Q000032:analysis / Q000494:pharmacology*; D010851:Picrates; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D018547:Plant Stems / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry*; D013045:Species Specificity
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D005419:Flavonoids; D010636:Phenols; D010851:Picrates; D010936:Plant Extracts; D009569:Nitric Oxide; C004931:1,1-diphenyl-2-picrylhydrazyl
keywords: HPLC; antioxidant activity; rice straw; seed husk