INTRODUCTION The plant kingdom has served as one of man’s oldest sources of useful drugs. They are remarkable in their ability to produce a vast number of diverse secondary metabolites ranging in chemical complexity and biological activities. Natural products (NPs) have historically served as templates for the modern drug development. The Garcinia species are known to be rich in ORIENTAL JOURNAL OF CHEMISTRY www.orientjchem.org Est. 1984 An International Open Free Access, Peer Reviewed Research Journal ISSN: 0970-020 X CODEN: OJCHEG 2013, Vol. 29, No. (3): Pg. 871-875 Antiplatelet Aggregation Activity of 5-Hydroxyflavone, 2’- Hydroxyflavanone, Paeonol and Bergenin Isolated from Stem Bark of Garcinia malaccensis in Human Whole Blood KHALED A.A. ALKADI 1 , AISHAH ADAM 1 , MUHAMMAD TAHA 2 , MIZATON HAZIZUL HASAN 2 and SYED ADNAN ALI SHAH 1,2 * 1 Faculty of Pharmacy, Universiti Teknologi MARA (UiTM), Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia. 2 Atta-ur-Rahman Institute for Natural Products Discovery, Universiti Teknologi MARA (UiTM), Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia. *Corresponding author E-mail: syedadnan@salam.uitm.edu.my/benzene301@yahoo.com DOI: http://dx.doi.org/10.13005/ojc/290304 (Received: July 16, 2013; Accepted: August 23, 2013) ABSTRACT Four known compounds, 5-Hydroxyflavone (1), 2’-Hydroxyflavanone (2), Paeonol (3) and bergenin (4), were isolated from the methanolic extract of the stem bark of Garcinia malaccensis for the first time through combination of vacuum and radial chromatography techniques. The structures of the secondary metabolites (1-4) were elucidated on the basis of their spectroscopic evidence and comparison with the published data. All isolated compounds exhibited inhibition of platelet aggregation in human whole blood which induced by arachidonic acid (AA), adenosine diphosphate (ADP) and collagen. 2’-Hydroxyflavanone (2) showed inhibitory effect on platelet aggregation caused by two inducers with IC 50 47.8± 2.1 AA and 147.2 ± 4.1 ADP. Key words: Garcinia malaccensis, Platelet aggregation, Impedance Method, Vacuum liquid chromatography (VLC), NMR spectroscopy. phytochemical contents such as flavonoids, phenolic acids and xanthones. G. Malaccensis Hk.f (Guttiferae), locally known as “manggis burung” is a member of the Guttiferae family. Its fruit much resembles that of G. mangostana and G. hombroniana. Its mature fruit is similar in size to G. hombroniana but smaller than G. Mangostana 1 . Mangosteen fruits from Garcinia malaccensis (G. Mangostana Hook. f.) Linn also known as the queen of fruit is a most popular xanthone-rich and edible