during our screening of tropical plants for endophyte microorganisms, a xylareaceous fungus was found living on the internal part of sapindus saponaria fruits. the fruits of s. saponaria accumulate great amounts of triterpenoidal and sesquiterpenoidal saponins. the saponin 3-o-(β-d-xylopyranosyl)-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl-hederagenin was isolated using chromatographic methods, after alkaline hydrolysis of the crude extract obtained from s. saponaria fruits and added to the culture medium used to grows the fungus. a new saponin was isolated from this experiment by preparative scale hplc and characterized as a 22α-hydroxy derivative. the structure of this hydroxylated saponin was elucidated based on interpretation of ms/ms data and nmr spectra.