Yoshihiro Mimaki

Three new spirostanol glycosides (1—3) and a new furostanol glycoside (4), together with two known spirostanol glycosides (5 and 6) were isolated from the whole plants of Agave utahensis (Agavaceae). The structures of the new compounds were determined by spectroscopic analysis and the results of hydrolytic cleavage.

The stems of Akebia quinata have been analyzed for their triterpene glycoside constituents, resulting in the isolation of six new triterpene glycosides, along with 19 known ones. On the basis of extensive spectroscopic analysis, including 2D NMR data, and chemical evidence, the structures of the new compounds were deter-mined to be 3β-[(O-β-D-glucuronopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-29-hydroxyolean-12-en-28-oic acid, and 3β-[(O-β-D-glucopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-23,29-dihydroxyolean-12-en-28-oic acid, respectively. The main triterpene glycosides contained in the stems of A. quinata were found to have two sugar units at C-3 and C-28 of the aglycone in this study, whereas those of Akebia trifoliate were reported to possess one sugar unit at C-28 of the aglycone. It may be possible to distinguish between A. quinata and A. trifoliate chemically by comparing their triterpene glycoside constituents.

Two new cycloartane glycosides, named neocimicigenosides A (1) and B (2), were isolated from the rhizomes of Cimicifuga racemosa. The structures of 1 and 2 were determined on the basis of extensive spectroscopic analysis and enzymatic hydrolysis followed by chromatographic and spectroscopic analyses to be (16S,23R,24S)-24-acetoxy-16,23:16,25-diepoxy-15α-hydroxycycloartan-3β-yl α-l-arabinopyranoside (1) and (16S,23R,24S)-24-acetoxy-16,23:16,25-diepoxy-15α-hydroxycycloartan-3β-yl β-d-xylopyranoside (2), respectively. Neocimicigenosides A and B enhanced CRF-stimulated ACTH secretion from AtT-20 cells.

A saponin-enriched fraction prepared from the MeOH extract of the roots of Clematis chinensis showed cytotoxic activity against HL-60 promyelocytic leukemia cells, from which five new triterpene saponins (1−5) based on oleanolic acid, along with three known saponins (6−8), were isolated. The structures of the new saponins were determined on the basis of spectroscopic analysis, including extensive 1D and 2D NMR data and hydrolysis followed by chromatographic and spectroscopic analysis. Among the isolated saponins, monodesmosidic saponins exhibited cytotoxic activities against cultured tumor cells.

Seven new bisdesmosidic triterpene saponins, with up to eight monosaccharides, which were given the trivial names contortisiliosides A–G (1–7), were isolated from Enterolobium contortisiliquum. The structures of the new saponins were determined on the basis of extensive spectroscopic and chromatographic analyses of both intact and acid‐hydrolyzed compounds. The isolated saponins were evaluated for their cytotoxic activities against BAC1.2F5 mouse macrophages, EL‐4 mouse lymphoma cells, and L‐929 mouse fibroblasts. Whereas contortisiliosides A (1) and C (3) were moderately cytotoxic to both BAC1.2F5 macrophages and EL‐4 cells, and contortisiliosides D–G (4–7) did not show any apparent cytotoxic activities against the three cell lines, contortisilioside B (2) exhibited selective cytotoxic activity against BAC1.2F5 mouse macrophages, with an IC₅₀ value of 3.4 μM. The macrophage death caused by 2 was shown to be neither necrotic nor apoptosis‐inducing based on the unique morphological change of the killed cells, whose cytosols were transformed into large vacuoles, and according to the TUNEL assay.

The two new polyoxygenated spirostanol bisdesmosides 1 and 2 and the new trisdesmoside 3, named hellebosaponin A (1), B (2), and C (3), respectively, were isolated from the MeOH extract of the rhizomes of Helleborus orientalis. The structures of the new compounds were elucidated as (1β,3β,23S,24S)‐21‐(acetyloxy)‐24‐[(β‐D‐fucopyranosyl)oxy]‐3,23‐dihydroxyspirosta‐5,25(27)‐dien‐1‐yl O‐β‐D‐apiofuranosyl‐(1→3)‐O‐(4‐O‐acetyl‐α‐L‐rhamnopyranosyl)‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐α‐L‐arabinopyranoside (1), (1β,3β,23S,24S)‐ 21‐(acetyloxy)‐24‐{[O‐β‐D‐glucopyranosyl‐(1→4)‐β‐D‐fucopyranosyl]oxy}‐3,23‐dihydroxyspirosta‐5,25(27)‐dien‐1‐yl O‐β‐D‐apiofuranosyl‐(1→3)‐O‐(4‐O‐acetyl‐α‐L‐rhamnopyranosyl)‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐ α‐L‐arabinopyranoside (2), and (1β,3β,23S,24S)‐24‐[(β‐D‐fucopyranosyl)oxy]‐21‐{[O‐β‐D‐glucopyranosyl‐(1→2)‐β‐D‐galactopyranosyl]oxy}‐3,23‐dihydroxyspirosta‐5,25(27)‐dien‐1‐yl O‐β‐D‐apiofuranosyl‐(1→3)‐O‐(4‐O‐acetyl‐α‐L‐rhamnopyranosyl)‐(1→2)‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐α‐L‐arabinopyranoside (3), respectively, on the basis of detailed spectroscopic studies and chemical evidence.