title: Stevia rebaudiana Bertoni as a source of bioactive compounds: the effect of harvest time, experimental site and crop age on steviol glycoside content and antioxidant properties.
abstract: BACKGROUND
  This study was aimed at identifying the effect of harvest time, experimental site and crop age on the no-calorie sweetener steviol glycosides (SG) and on the antioxidant properties of stevia leaf extracts. The experiment was conducted over two growing seasons at two sites in the northeastern plain of Italy.
  
  
  RESULTS
  The results showed that all analysed factors played an important role in defining the SG profile and the antioxidant properties of stevia extracts. A high level of phenols (78.24 mg GAE g⁻¹ DW by Folin-Ciocalteu method) and high antioxidant activity (812.6 µmol Fe²⁺ g⁻¹ DW by FRAP assay) were observed. The inhibition of DPPH free radicals was evaluated and an IC₅₀ mean value of 250 µg mL⁻¹ was obtained. Significant relationships among the total antioxidant capacity and the analysed compounds were found.
  
  
  CONCLUSIONS
  The results showed the possibility of obtaining, in the tested environments, very high SG yields thanks to the long-day conditions during the spring/summer season. The harvest time played a key role in determining the stevia quality, influencing the rebaudioside A/stevioside ratio. The strong antioxidant properties make very interesting the possibility of using stevia extracts to improve functional food properties.
authors.affiliation: Department of Agriculture, Food and Environment, The University of Pisa, Via S Michele degli Scalzi 2, I-56124 Pisa, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Tavarini
authors.forename: Luciana G
authors.initials: LG
authors.lastname: Angelini
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D018556:Crops, Agricultural / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D045786:Diterpenes, Kaurane / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D005503:Food Additives / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D005960:Glucosides / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D006027:Glycosides / Q000032:analysis / Q000378:metabolism; D007558:Italy; D064306:Non-Nutritive Sweeteners / Q000032:analysis / Q000378:metabolism; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010636:Phenols / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D064209:Phytochemicals / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D012621:Seasons; D012987:Soil / Q000737:chemistry; D062211:Spatio-Temporal Analysis; D036625:Stevia / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism
chemical_list: D000975:Antioxidants; D045786:Diterpenes, Kaurane; D005503:Food Additives; D005960:Glucosides; D006027:Glycosides; D064306:Non-Nutritive Sweeteners; D009844:Oligosaccharides; D010636:Phenols; D064209:Phytochemicals; D010936:Plant Extracts; D012987:Soil; C012043:stevioside; C012042:steviol; C025474:rebaudioside A; C524468:rebaudioside C