title: Identification of the compositional changes in Orthosiphon stamineus leaves triggered by different drying techniques using1H NMR metabolomics.
abstract: BACKGROUND
  Java tea is a well-known herbal infusion prepared from the leaves of Orthosiphon stamineus (OS). The biological properties of tea are in direct correlation with the primary and secondary metabolite composition, which in turn largely depends on the choice of drying method. Herein, the impact of three commonly used drying methods, i.e. shade, microwave and freeze drying, on the metabolite composition and antioxidant activity of OS leaves was investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy combined with multivariate classification and regression analysis tools.
  
  
  RESULTS
  A total of 31 constituents comprising primary and secondary metabolites belonging to the chemical classes of fatty acids, amino acids, sugars, terpenoids and phenolic compounds were identified. Shade-dried leaves were identified to possess the highest concentrations of bioactive secondary metabolites such as chlorogenic acid, caffeic acid, luteolin, orthosiphol and apigenin, followed by microwave-dried samples. Freeze-dried leaves had higher concentrations of choline, amino acids leucine, alanine and glutamine and sugars such as fructose and α-glucose, but contained the lowest levels of secondary metabolites.
  
  
  CONCLUSIONS
  Metabolite profiling coupled with multivariate analysis identified shade drying as the best method to prepare OS leaves as Java tea or to include in traditional medicine preparation. © 2017 Society of Chemical Industry.
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Raghunath
authors.identifier: http://orcid.org/0000-0003-4321-5362
authors.initials: R
authors.lastname: Pariyani
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.|Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Intan Safinar
authors.initials: IS
authors.lastname: Ismail
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Amalina
authors.initials: A
authors.lastname: Ahmad Azam
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.|Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Faridah
authors.initials: F
authors.lastname: Abas
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.|Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Khozirah
authors.initials: K
authors.lastname: Shaari
mesh_terms: D003890:Desiccation; D005511:Food Handling; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D055432:Metabolomics; D031342:Orthosiphon / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*
chemical_list: D010936:Plant Extracts
keywords: HPLC/MS/MS; Java tea; Orthosiphon stamineus; antioxidant activity; drying methods; proton nuclear magnetic resonance