title: Evaluation, prediction and optimization the ultrasound-assisted extraction method using response surface methodology: antioxidant and biological properties of Stachys parviflora L.
abstract: OBJECTIVE
  To optimize the extraction method using response surface methodology, extract the phenolic compounds, and identify the antioxidant and biological properties of Stachys parviflora L. extracts.
  
  
  METHODS
  Maceration and ultrasound-assisted extraction (UAE) (4, 7, 10 min treatment time, 40, 70, 100 % high-intensity and 60, 80, 100 % (v v-1) methanol purity) were applied to obtain the extracts. SEM was conducted to provide the microstructure of the extracted plant. MICs (colorimetric assay), MFCs (colony diameter), total phenolic content, total flavonoid content, radical scavenging capacity and extraction efficiency were determined. HPLC analysis was applied to measure the existent phenolic compounds.
  
  
  RESULTS
  A quadratic model (4 min treatment time, 74.5 % high-intensity and 74.2 % solvent purity) was suggested as the best (TPC: 20.89 mg GAE g-1 d.m., TFC: 6.22 mg QEs g-1 d.m., DPPH IC50: 21.86 µg ml-1 and EE: 113.65 mg g-1 d.m.) UAE extraction model. The optimized UAE extract was generally more effective against Gram-positive microorganisms (MIC: 10-20; MBC: 10-40 (mg ml-1)) than Gram-negative ones (MIC: 40; MBC: >40 (mg ml-1)). Moreover, it (MGI: 2.32-100 %) revealed more anti-mold activity than maceration (MGI: <28.77 %). Explosive disruption of the cell walls, therefore, enhanced extraction yield by acoustic cavitation, was elucidated using SEM. Caffeic acid, tannic acid, quercetin, trans ferulic acid and rosmarinic acid were determined as the phenolic compounds in the optimized extract.
  
  
  CONCLUSIONS
  RSM optimization was successfully applied for UAE from S. parviflora. The considerable antioxidant and biological properties were attributed to the phenolic compounds.
authors.affiliation: School of Medicine, Gonabad University of Medical Sciences, Gonabad, Iran; Ferdowsi University of Mashhad, International campus, Department of Food Science and Technology, Mashhad, Iran.
authors.forename: Davoud Salar
authors.initials: DS
authors.lastname: Bashi
authors.affiliation: Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran.
authors.forename: Samaneh Attaran
authors.initials: SA
authors.lastname: Dowom
authors.affiliation: School of Pharmacy; Biotechnology Research Center; Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Bibi Sedigheh Fazly
authors.initials: BS
authors.lastname: Bazzaz
authors.affiliation: Department of Food Science and Technology, Sabzevar Branch, Islamic Azad University, Sabzevar, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Khanzadeh
authors.affiliation: Department of Food and Drug Control, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Soheili
authors.affiliation: Medical Surgical Nursing, Social Determinant of Health Center, Gonabad University of Medical Sciences, Gonabad, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Mohammadpour
keywords: Antioxidant; Biological properties; HPLC; RSM; Stachys parviflora L; ultrasound-assisted extraction