Structural features of polysaccharides from edible jambo (Syzygium jambos) fruits and antitumor activity of extracted pectins

Jambo is a tropical fruit cultivated in Southeast Asia and tropical regions of America and Africa. After extraction, its polysaccharides were structurally characterized. Water soluble polysaccharides (WSP) were composed of GalA:Ara:Gal:Glc:Rha in 51:22:16:5:6 molar ratio, indicating the presence of pectic polysaccharides. Methylation analysis and NMR spectroscopy indicated the presence of homogalacturonan (HG), type II arabinogalactan and type I rhamnogalacturonan (RG-I). The HG/RG-I ratio was 88%, indicating greater amounts of smooth than hairy pectic regions. Hemicellulosic polysaccharides were extracted from the residue and fractionated by freeze-thaw procedure in two fractions (ASP-S and ASP-I). ASP-S was composed of Glc:Gal:Xyl:Ara:Man:Fuc:UA in a 45:16:20:3:8:5:2 molar ratio. Methylation analysis and 13C NMR spectroscopy indicated xyloglucan, xylan and mannan. Their relative proportion estimated on sugar linkage was 89%, 6% and 3%, respectively. ASP-I was composed mainly of xylose (99.5%) and its 13C NMR indicated a linear (1 → 4)-β-D-xylan. The biological activity of WSP was tested in Ehrlich tumor-bearing mice. After 21 days of oral treatment, the doses of 150 and 250 mg/kg WSP reduced expressively the tumor growth, similarly to the positive control methotrexate, and improved the body weight of tumor-bearing mice. Further studies are necessary to investigate the mechanisms of the WSP antitumor effect.