Haemolytic acylated triterpenoid saponins from Harpullia austro-caledonica
Abstract
Eight new acylated triterpenoid saponins were isolated from the stem bark of Harpullia austro-caledonica along with the known harpuloside (9). Their structures were established using 1D and 2D NMR and mass spectrometry as 3-O-β-d-galactopyranosyl-(1 → 2)-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylbarringtogenol C (1), 3-O-α-l-rhamnopyranosyl-(1 → 3)-[β-d-galactopyranosyl-(1 → 2)]-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloyl barringtogenol C (2), 3-O-α-l-arabinofuranosyl-(1 → 3)-[β-d-galactopyranosyl-(1 → 2)]-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylbarringtogenol C (3), 3-O-α-l-arabinofuranosyl-(1 → 2)-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylprotoaescigenin (4), 3-O-α-l-arabinofuranosyl-(1 → 3)-[α-l-arabinofuranosyl-(1 → 2)]-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloyl protoaescigenin (5), 3-O-α-l-arabinofuranosyl-(1 → 3)-[β-d-xylopyranosyl-(1 → 2)]-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylprotoaescigenin (6), 3-O-α-l-arabinofuranosyl-(1 → 3)-[β-d-glucopyranosyl-(1 → 2)]-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylprotoaescigenin (7), 3-O-β-d-xylopyranosyl-(1 → 2)-β-d-glucuronopyranosyl-21β, 22α-di-O-angeloylprotoaescigenin (8).
The EtOH extract of the stem bark showed in vitro cytotoxic activity against KB cells (90% at 10 μg/ml). At a concentration of 5 μg/ml, the saponin mixture showed haemolytic activity and caused 100% haemolysis of a 10% suspension of sheep erythrocytes.
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