title: Antioxidant and cytotoxic activities of three species of tropical seaweeds.
abstract: BACKGROUND
  Three species of seaweeds (Padina tetrastromatica, Caulerpa racemosa and Turbinaria ornata) are widely consumed by Asians as nutraceutical food due to their antioxidant properties. Studies have shown that these seaweeds exhibit bioactivities which include antimicrobial, antiviral, anti-hypertensive and anticoagulant activities. However, investigations into the mechanisms of action pertaining to the cytotoxic activity of the seaweeds are limited. The aim of this study was to determine the antioxidant and cytotoxic activities of whole extracts of P. tetrastromatica, C. racemosa and T. ornata, including the cellular events leading to the apoptotic cell death of the extract treated-MCF-7 cells. Bioassay guided fractionation was carried out and the compounds identified.
  
  
  METHODS
  Powdered samples were sequentially extracted for 24 h. Their antioxidant activities were assessed by the DPPH radical, superoxide, nitric oxide and hydroxyl radical scavenging assays. The cytotoxic activity of the extract-treated MCF-7cells was assessed using the MTT assay. The most potent fraction was subjected to bioassay guided fractionation with column chromatography. All the fractions were tested for cytotoxic activity, caspase activity and effect on DNA fragmentation.
  
  
  RESULTS
  All three seaweeds showed potent radical scavenging activities in the various assays. The activity of the cellular antioxidant enzymes, superoxide dismutase, catalase and glutathione reductase, in MCF-7 cells, decreased in a time-dependent manner. The partially purified fractions exhibited higher cytotoxic activity, as assessed by the MTT assay, than the whole extracts in the breast adenocarcinoma cell line, MCF-7. LC-MS analysis revealed the presence of bioactive alkaloids such as camptothecin, lycodine and pesudopelletierine.
  
  
  CONCLUSIONS
  Based on the results obtained, all three seaweeds are rich sources of enzymatic and non-enzymatic antioxidants which could contribute to their reported medicinal benefits.
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. gracechia1986@hotmail.com.
authors.forename: Yin Yin
authors.initials: YY
authors.lastname: Chia
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. kanthi@ummc.edu.my.|University of Malaya Centre for Proteomics Research (UMCPR), University of Malaya, Kuala Lumpur, Malaysia. kanthi@ummc.edu.my.
authors.forename: M S
authors.initials: MS
authors.lastname: Kanthimathi
authors.affiliation: Department of Chemical Science, Faculty of Science, Universiti Tunku Abdul Rahman (Kampar campus), Jalan Universiti, Bandar Barat, 31900, Kampar, Perak, Malaysia. khooks@utar.edu.my.
authors.forename: Kong Soo
authors.initials: KS
authors.lastname: Khoo
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. jayakumar7979@gmail.com.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Rajarajeswaran
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. chenghm@ummc.edu.my.
authors.forename: Hwee Ming
authors.initials: HM
authors.lastname: Cheng
authors.affiliation: Department of Biotechnology, Faculty of Applied Sciences, UCSI University, 56000 UCSI Heights, Kuala Lumpur, Malaysia. wsyap@ucsi.edu.my.
authors.forename: Wai Sum
authors.initials: WS
authors.lastname: Yap
mesh_terms: D000959:Antihypertensive Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002374:Catalase / Q000378:metabolism; D006801:Humans; D061986:MCF-7 Cells; D010084:Oxidation-Reduction; D000459:Phaeophyceae / Q000737:chemistry; D010936:Plant Extracts / Q000494:pharmacology*; D012624:Seaweed / Q000737:chemistry*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000959:Antihypertensive Agents; D000975:Antioxidants; D010936:Plant Extracts; D002374:Catalase; D013482:Superoxide Dismutase