PhytoScience - Science 
Anti-oxidant - Invitro
Oligomeric proanthocyanidins from mangosteen pericarps.
Fu C, Loo AE, Chia FP, Huang D.
Department of Chemistry, National University of Singapore, 3 Science Drive 3,
Singapore 117543, Republic of Singapore.
Oligomeric proanthocyanidins were extracted from mangosteen pericarps and fractionated by a Sephadex LH-20 column to give 0.66% yield (dry matter). (13)C and (1)H NMR signals showed the presence of predominantly procyanidins together with a few prodelphinidin units along with small amounts of stereoisomers of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin.
Depolymerization with benzylmercaptan resulted in epicatechin thioether as the major product, and the mean degree of polymerization was determined to be 6.6.
The electron spray ionization-mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectra revealed the dominant B type oligomers with mainly epicatechin units and with a small amount of A type oligomers.
The isolated proanthocyanidins are potent peroxyl radical scavengers as evidenced by the high oxygen radical scavenging capacity at 1.7 x 10 (4) micromol TE/g, much higher than that of pine bark and grape seed extracts.
PMID: 17715900 [PubMed - indexed for MEDLINE]
Anti-oxidant - Invitro
Xanthones with quinone reductase-inducing activity from the fruits of Garcinia mangostana (Mangosteen).
Chin YW, Jung HA, Chai H, Keller WJ, Kinghorn AD.
Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy,
The Ohio State University,
Columbus, OH 43210, USA.
Bioactivity-guided fractionation of a dichloromethane-soluble extract of Garcinia mangostana fruits has led to the isolation and identification of five compounds, including two xanthones, 1,2-dihydro-1,8,10-trihydroxy-2-(2-hydroxypropan-2-yl)-9-(3-methylbut-2-enyl)furo[3,2-a]xanthen-11-one (1) and 6-deoxy-7-demethylmangostanin (2), along with three known compounds, 1,3,7-trihydroxy-2,8-di-(3-methylbut-2-enyl)xanthone (3), mangostanin (4), and alpha-mangostin (5).
The structures of compounds 1 and 2 were determined from analysis of their spectroscopic data. All isolated compounds in the present study together with eleven other compounds previously isolated from the pericarp of mangosteen, were tested in an in vitro quinone reductase-induction assay using murine hepatoma cells (Hepa 1c1c7) and an in vitro hydroxyl radical antioxidant assay.
Of these, compounds 1-4 induced quinone reductase (concentration to double enzyme induction, 0.68-2.2mug/mL) in Hepa 1c1c7 cells and gamma-mangostin (6) exhibited hydroxyl radical-scavenging activity (IC(50), 0.20mug/mL).
PMID: 17991497 [PubMed - in process]