title: Influence of extraction conditions on antioxidant properties of passion fruit (Passiflora edulis) peel.
abstract: BACKGROUND
  As a by-product of tropical fruit juice industry, passion fruit peel is a valuable functional food. It is rich in antioxidants. To determine its potential antioxidant properties of passion fruit peel, this study aimed to evaluate the effect of extraction conditions on total phenolic content and antioxidant activity.
  
  
  METHODS
  The extraction conditions were selected from different percentages of ethanol (0-100%, v/v), extraction times (60-300 min), and extraction temperatures (25-60°C) that based on the optimal percentage of DPPH radical scavenging activity. The selected extraction condition was applied for further determination of total phenolic content (TPC) of the passion fruit peel extract using Folin-Ciocalteu reagent assay, while the antioxidant activities were evaluated using DPPH and ABTS radicals scavenging assays, ferric reducing antioxidant power (FRAP), and β-carotene bleaching (BCB) assay. The best extraction conditions were 40% ethanol, 60 min extraction time, and extraction temperature of 30°C.
  
  
  RESULTS
  The chosen extraction conditions have contributed to the high TPC and antioxidant activity of passion fruit peel. The levels of antioxidant activity obtained from the passion fruit peel were also lower compared to BHA and α-tocopherol. Positive correlations were observed between TPC and antioxidant activities as assessed by DPPH, ABTS, FRAP, and BCB assays.
  
  
  CONCLUSIONS
  As a waste of passion fruit consumption or by-product of fruit juice industry, its peel could be considered as a potential source of natural antioxidant for possible functional food and industrial applications.
authors.affiliation: Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, Kuala Lumpur.
authors.forename: Yuh Shan
authors.initials: YS
authors.lastname: Wong
authors.affiliation: Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, Kuala Lumpur.
authors.forename: Chiaw Mei
authors.initials: CM
authors.lastname: Sia
authors.affiliation: Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, Kuala Lumpur, Malaysia.
authors.forename: Hock Eng
authors.initials: HE
authors.lastname: Khoo
authors.affiliation: Perdana University Graduate School of Medicine, Selangor, Malaysia.
authors.forename: Yee Kwang
authors.initials: YK
authors.lastname: Ang
authors.affiliation: Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia.
authors.forename: Sui Kiat
authors.initials: SK
authors.lastname: Chang
authors.affiliation: Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia.
authors.forename: Sui Kiat
authors.initials: SK
authors.lastname: Chang
authors.affiliation: Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, Kuala Lumpur, Malaysia.
authors.forename: Hip Seng
authors.initials: HS
authors.lastname: Yim
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis*; D052160:Benzothiazoles / Q000032:analysis; D016166:Free Radical Scavengers / Q000032:analysis; D005638:Fruit / Q000737:chemistry*; D029598:Passiflora / Q000737:chemistry*; D010636:Phenols / Q000032:analysis*; D019441:Plant Epidermis / Q000737:chemistry*; D010936:Plant Extracts / Q000032:analysis*; D013451:Sulfonic Acids / Q000032:analysis; D019207:beta Carotene / Q000032:analysis
chemical_list: D000975:Antioxidants; D052160:Benzothiazoles; D016166:Free Radical Scavengers; D010636:Phenols; D010936:Plant Extracts; D013451:Sulfonic Acids; D019207:beta Carotene; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid