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Structural C omposition and Free Radical Scavenging Activity of Proanthocyanidins Extracted from Grevillea robusta

Shu-Dong Wei, Yi-Ming Lin, Meng-Meng Liao, Wei-Ming Chai, and Hai-Chao Zhou

Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen 361005, China

Abstract: The aim of this study was to investigate polymeric proanthocyanidin (PA) composition and free radical scavenging activity of leaf, stem bark and fine root of Grevillea robusta. The spectra obtained through MALDI-TOF MS analysis revealed that the examined PAs were built up a mixture of procyanidins and prodelphinidins. Acid-catalyzed cleavage of the PAs coupled with reversed-phase HPLC-ESI-MS showed that the mainconstituents of cleavage products were (epi) gallocatechin benzylthioether and (epi)catechin benzylthioether for leaf and stem bark, and was (epi)gallocatechin benzylthioether for fine root, respectively. The mean degree s of polymerization (mDP) of PAs of leaf, stem bark and fine root were 9.6, 19.0 and 10.1, respectively. The PAs extracted from leaf, stem bark and fine root exhibit ed higher antioxidant activity than those of ascorbic acid and synthetic antioxidant butylated hydroxyanisole (BHA) , as measured by 2,2 '-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging method.

Keywords: Grevillea robusta ; proanthocyanidin s; MALDI-TOF MS ; thiolysis; ABTS.