Non-cellulosic polysaccharides from the leaves of small balsam (Impatiens parviflora DC.)

•Pre-extracted Impatiens parviflora DC. leaves were subjected to five-step extraction.•The methanol extract contains caffeic acid, ferulic acid, and kaempferol derivatives.•Several non-cellulosic polysaccharides and phenolics were isolated.•A low methoxyl pectin and β-1,4-galactan were extracted by EDTA.•Methylglucuronoxylan and 3,6-arabinogalactan were isolated by 5% NaOH.

The leaves of the annual plant Impatiens parviflora DC., a herbal medicine in Asian countries and invasive in managed forests and natural environments in Central Europe, have the potential as a source of bioactive phenolic compounds and polysaccharides. Extractives accounted for ∼22% of the leaves, whereby, the methanolic extract contains mainly caffeic acid, ferulic acid, kaempferol, and quercetin derivatives, and 1,2,4-trihydroxynaphthalene-1-O-glucoside. From the pre-extracted leaves, non-cellulosic polysaccharides were isolated by a five-step extraction procedure using as extractants cold water, 0.05 M EDTA, and DMSO in the first three steps, and 1% and 5% NaOH in the last two steps. The isolated polysaccharide fractions were characterized by chemical, physicochemical, and spectroscopic analyses (FTIR and 1H NMR). The first three fractions contained mainly pectin and the alkali-extracted ones methylglucuronoxylan and arabinogalactan. The suggested structural features were confirmed using HSQC NMR and COSY experiments for polysaccharides of the EDTA-fraction and the Pronase-treated 5% NaOH-fraction. The EDTA fraction comprised a pectin with low degree of methyl-esterification (DM, 37%) with few rhamnogalacturonan RG I segments bearing β-1,4-galactan as side chains. The alkali-extracted fraction comprised a degraded methylglucuronoxylan and type II 3,6-arabinogalactan in about equal amounts.

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