Objective To investigate the chemical constituents in the aerial parts of mangrove plant Avicennia marina. Methods The isolated compounds Ⅰ-Ⅹ were obtained by the combination of silica gel, Sephadex LH-20 column chromatographies and by semi-preparative HPLC separation. Structural elucidation was conducted by the modern spectral method. Results Ten compounds were isolated and identified from the aerial parts of A. marina, including acteoside (Ⅰ), isoacteoside (Ⅱ), syringaresinol (Ⅲ), 5, 7-dihydroxy-3′, 4′, 5′-trimethoxyflavone (Ⅳ), indolyl-3-carboxylic acid (Ⅴ), betulinic acid (Ⅵ), betullin (Ⅶ), lupeol (Ⅷ), avicequinone C (Ⅸ), and kaempferol (Ⅹ). Conclusion Compounds Ⅰ-Ⅵ are isolated from A. marina for the first time.

Objective To report a method for preparation of saturated oligosaccharides from al- ginate. Methods The alginate was degraded by acid hydrolysis, followed by fractionation at pH 2.85 resulting in the homopolyguluronic acids (PG) and homopolymannuronic acids (PM). The alginate-derived homopolymers were further degraded by acid hydrolysis at pH 3.8, 120 ℃ for 3 h, and at pH 4, 120 ℃ for 4 h, respectively. The resulted acidic hydrolysates were separated by gel permeation chromatography to get oligosaccharide fractions, and the oligosaccharides were obtaind by repeated purification on gel chromatography. The structures of the oligosaccharides were characterized by analyses of infra-red spectroscopy (IR), nuclear magnetic resonance spectrometry (NMR), and mass spectrometry (MS). Results It was showed that the derived oligosaccharides were in saturated structures with the same structure characteristics as the original alginate macromolecule. Conclusion The method des cribed in this paper is a effective and convenient approach for the preparation of low-molecular-weight oligosaccharides from alginate.