title: Unique bioactive polyphenolic profile of guava (Psidium guajava) budding leaf tea is related to plant biochemistry of budding leaves in early dawn.
abstract: BACKGROUND
  Guava leaf tea (GLT), exhibiting a diversity of medicinal bioactivities, has become a popularly consumed daily beverage. To improve the product quality, a new process was recommended to the Ser-Tou Farmers' Association (SFA), who began field production in 2005. The new process comprised simplified steps: one bud-two leaves were plucked at 3:00-6:00 am, in the early dawn period, followed by withering at ambient temperature (25-28 °C), rolling at 50 °C for 50-70 min, with or without fermentation, then drying at 45-50 °C for 70-90 min, and finally sorted.
  
  
  RESULTS
  The product manufactured by this new process (named herein GLTSF) exhibited higher contents (in mg g(-1), based on dry ethyl acetate fraction/methanolic extract) of polyphenolics (417.9 ± 12.3) and flavonoids (452.5 ± 32.3) containing a compositional profile much simpler than previously found: total quercetins (190.3 ± 9.1), total myricetin (3.3 ± 0.9), total catechins (36.4 ± 5.3), gallic acid (8.8 ± 0.6), ellagic acid (39.1 ± 6.4) and tannins (2.5 ± 9.1).
  
  
  CONCLUSIONS
  We have successfully developed a new process for manufacturing GLTSF with a unique polyphenolic profile. Such characteristic compositional distribution can be ascribed to the right harvesting hour in the early dawn and appropriate treatment process at low temperature, avoiding direct sunlight.
authors.affiliation: Research Institute of Biotechnology, Hungkuang University, Shalu County, Taichung, 43302 Taiwan.
authors.forename: Chi-Huang
authors.initials: CH
authors.lastname: Chang
authors.forename: Chiu-Lan
authors.initials: CL
authors.lastname: Hsieh
authors.forename: Hui-Er
authors.initials: HE
authors.lastname: Wang
authors.forename: Chiung-Chi
authors.initials: CC
authors.lastname: Peng
authors.forename: Charng-Cherng
authors.initials: CC
authors.lastname: Chyau
authors.forename: Robert Y
authors.initials: RY
authors.lastname: Peng
mesh_terms: D000383:Agriculture / Q000379:methods*; D001628:Beverages; D002392:Catechin / Q000032:analysis; D004610:Ellagic Acid / Q000032:analysis; D005511:Food Handling / Q000379:methods; D005707:Gallic Acid / Q000032:analysis; D018515:Plant Leaves / Q000737:chemistry*; D028321:Plant Preparations / Q000737:chemistry; D059808:Polyphenols / Q000032:analysis*; D031647:Psidium / Q000737:chemistry*; D011794:Quercetin / Q000032:analysis; D013472:Sunlight; D013634:Tannins / Q000032:analysis; D013696:Temperature
chemical_list: D028321:Plant Preparations; D059808:Polyphenols; D013634:Tannins; D004610:Ellagic Acid; D005707:Gallic Acid; D002392:Catechin; D011794:Quercetin