Caspicaosides E-K, triterpenoid saponins and cytotoxic acylated saponins from fruits of Gleditsia caspica Desf.

Seven bisdesmosidic triterpenoid saponins named caspicaosides E-K, were isolated from the methanolic fruit extract of Gleditsia caspica Desf. Their structures were determined by 1D and 2D NMR spectroscopy as well as high resolution mass spectrometry and acid hydrolysis. The saponins comprised echinocystic acid or oleanolic acid as the aglycone and saccharide moieties at C-3 and C-28. Like most Gleditsia saponins, the oligosaccharide moiety at C-3 was identified as ß-D-xylopyranosyl-(1→2)-α-L-arabinopyranosyl-(1→6)-ß-D-glucopyranosyl. The common oligosaccharide moiety linked to C-28 was determined as ß-D-xylopyranosyl-(1→3)-ß-D-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-ß-D-glucopyranosyl with the presence of additional ß-D-galactopyranose unit and/or another α-L-rhamnopyranose moiety. The C-28 saccharide moiety was acylated with a monoterpenic acid unit or a monoterpenic acid linked to a monoterpene-arabinoside unit at the ester-ß-D-glucopyranose C-6. Esterification of C-2 and C-3 hydroxyl groups of the terminal α-L-rhamnopyranose unit with a monoterpenic acid and epoxy-monoterpenic acid units, respectively, or with two identical monoterpenic acid units, was also shown. The acylated saponins caspicaosides G-K were assayed for their in vitro cytotoxicities against the three cell lines HCT116, HepG2 and MCF7. The tested saponins showed moderate to strong activities.

Cytotoxic triterpenoid saponins acylated with monoterpenic acids from fruits of Gleditsia caspica Desf.

Four bisdesmosidic triterpenoid saponins named caspicaosides A-D, were isolated from the fruits of Gleditsia caspica Desf. Their structures were determined by NMR spectroscopy including HOHAHA, ¹H-¹H COSY, ROE, HMQC, HMBC experiments and HRFAB-MS as well as acid hydrolysis. The four 3,28-O-bisdesmosidic triterpenoid saponins comprised echinocystic acid as the aglycone and common oligosaccharide moieties at C3 and C28. The saccharide moiety at C-3 was identified as ß-D-xylopyranosyl-(1→2)-α-L-arabinopyranosyl-(1→6)-ß-D-glucopyranosyl while that at C-28 was determined as ß-D-xylopyranosyl-(1→3)-ß-d-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→6)-]ß-D-glucopyranosyl. The pentasaccharide moiety linked to C-28 was acylated with monoterpenic acid and or monoterpene-arabinoside moieties at C-2 or C-2 and C-3 of the terminal rhamnose unit. The isolated saponins were assayed for their in vitro cytotoxicities against the three human tumor cell lines HepG2, A549 and HT29 using MTT method. The results showed that caspicaosides B and C bearing two and three monoterpene units, respectively, exhibited significant cytotoxic activities against the used cell lines with IC50 values 1.5-6.5 µM. Caspicaosides A and D with one monoterpene unit exhibited significant cytotoxic activities on HepG2 cell line with IC50 values equal to 4.5 and 5.4 µM, respectively, and IC50 values > 10 µM against the other two cell lines. The number of monoterpene units seems to play a main role in determining the activity.