Isolation, NMR characterization and bioactivity of a (4-O-methyl-α-D-glucurono)-β-D-xylan from Campomanesia xanthocarpa Berg fruits

Hemicellulose-type polysaccharides were isolated from Campomanesia xanthocarpa fruits by alkaline extraction and submitted to fractionation processes giving rise to eluted (GE-300) and retained (GR-300) fractions. GE-300 presented a mixture of galactoglucomannans (GGM) and glucuronoxylans (MGX), while the GR-300 fraction is composed only of MGX. In this way, the chemical structure of MGX, investigated by 1D H-1, C-13 and 2D H-1-C-13 HSQC, H-1-H-1 COSY and H-1-C-13 HMBC NMR spectroscopy, revealed that the chemical structure of polysaccharide is a (4-O-methyl-alpha-D-glucurono)-D-xylan. Deep and precise NMR chemical shift determination of clean and specific H-1 NMR glycosyl units were developed by 1D TOCSY and 1D NOESY analysis. This approach demonstrated unequivocally that 4-O-methyl-alpha-D-glucopyranosyl uronic acid group is linked to O-2 of a (1 -> 4)-beta-D-xylan in the main chain. Furthermore, MGX scavenged DPPH radical (0.5 to 1.0 mg mL(-1)) and was not cytotoxic to human dermal fibroblasts at concentrations up to 1.0 mg mL(-1), as demonstrated by neutral red and crystal violet assays, evidencing in vitro biocompatibility. The structure elucidation of GR-300 together with its bioactivity assessment contributed to better understand the chemical characteristics of C. xanthocarpa hemicelluloses and may provide structural basis for future structure-property studies.

Automated summary

Hemicellulose-type polysaccharides were isolated from Campomanesia xanthocarpa fruits and separated into two fractions. The chemical structure of the polysaccharide was determined to be a (4-O-methyl-alpha-D-glucurono)-D-xylan. The MGX fraction exhibited antioxidant activity and was biocompatible with human dermal fibroblasts.