New terpenoid glycosides from Eriocoelum microspermum

The family of Sapindaceae includes more than 2000 species which are distributed into three sub-families and fourteen tribes. A chemical investigation of the hydro-ethanolic extract of the stems of Eriocoelum microspermum Radlk. ex Wild (Sapindoideae sub-family and Cupianeae tribe) from the Democratic Republic of Congo, led to the isolation of six new glycosidic compounds. Their structures were established mainly by extensive 1D and 2D NMR and mass spectroscopic analysis. Three new triterpene saponins and a known one were characterized as hederagenin derivatives, glycosylated by 3 to 5 sugars at the C-3 of the aglycone. The partial sequence 3-O-α-L-rhamnopyranosyl-(1 – 2)-α-L-arabinopyranosylhederagenin was shown to possess additional glycosylations by α-L-rhamnopyranosyl and/or β-D-xylopyranosyl units. This sequence already encountered in other genera than Eriocoelum, particularly Sapindus, Lecaniodiscus, Ellatostachys, Smelophyllum, may represent a chemotaxonomic marker for the Sapindoidae sub-family [1],[2]. Furthermore, two new glycosides of farnesol, an acyclic sesquiterpene alcohol, with 6 sugars (glc, rha, ara, xyl), were isolated. The partial sequence rha¹-⁶glc¹-¹farnesol rarely described in the literature, was already found in three species of the genus Sapindus (Sapindoideae). This presentation shows that two classes of terpenoid glycosides characterized in Eriocoelum microspermum are relevant for the chemotaxonomy of the Sapindoideae.

[1] Delaude, C. Bull. Soc. Roy. Sci. Liège 1993, 62: 93 – 120.

[2] Voutquenne-Nazabadioko, L. Ethnopharmacologia 2010, 45: 49 – 52.