title: Ultrasound-assisted extraction of antioxidants in Misai Kucing (Orthosiphon stamineus).
abstract: Ultrasound-assisted extraction (UAE) with ethanol was used to extract the compounds responsible for the antioxidant activities of Misai Kucing (Orthosiphon stamineus). Response surface methodology (RSM) was used to optimize four independent variables: ethanol concentration (%), amplitude (%), duty cycle (W/s) and extraction time (min). Antioxidant compounds were determined by total phenolic content and total flavonoid content to be 1.4 g gallic acid equivalent/100 g DW and 45 g catechin equivalent/100 g DW, respectively. Antioxidant activities were evaluated using the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) radical scavenging capacity assay and the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging capacity assay to be 1,961.3 and 2,423.3 µmol Trolox Equivalent Antioxidant Capacity (TEAC)/100 g DW, respectively. Based on the optimal conditions, experimental values were reported to be close to the predicted value by RSM modeling (p>0.05), indicating the suitability of UAE for extracting the antioxidants of Misai Kucing. Rosmarinic acid, kaempferol-rutinoside and sinesetine were identified by high performance liquid chromatography-mass spectrometry.
authors.affiliation: Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, UPM 43400, Serdang, Selangor, Malaysia. hkheng@hotmail.com.
authors.forename: Swee Kheng
authors.initials: SK
authors.lastname: Ho
authors.affiliation: Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, UPM 43400, Serdang, Selangor, Malaysia. tancp@upm.edu.my.
authors.forename: Chin Ping
authors.initials: CP
authors.lastname: Tan
authors.affiliation: School of Science, Monash University Malaysia, Bandar Sunway, Petaling Jaya 46150, Selangor, Malaysia. thoo.yin.yin@monash.edu.
authors.forename: Yin Yin
authors.initials: YY
authors.lastname: Thoo
authors.affiliation: Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, UPM 43400, Serdang, Selangor, Malaysia. faridah_abas@upm.edu.my.
authors.forename: Faridah
authors.initials: F
authors.lastname: Abas
authors.affiliation: Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, No. 1, Jalan Menara Gading, UCSI Heights, Cheras 56000, Kuala Lumpur, Malaysia. cwho@ucsiuniversity.edu.my.
authors.forename: Chun Wai
authors.initials: CW
authors.lastname: Ho
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification*; D005609:Free Radicals / Q000737:chemistry; D031342:Orthosiphon / Q000737:chemistry*; D010851:Picrates / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification*; D013010:Sonication; D013451:Sulfonic Acids / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D010851:Picrates; D010936:Plant Extracts; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C004931:1,1-diphenyl-2-picrylhydrazyl