Tubeimoside I, a new cyclic bisdesmoside from Chinese cucurbitaceous folk medicine "tu bei mu", a tuber of Bolbostemma paniculatum

Tubeimoside I induces autophagy in HepG2 cells by activating the AMP-activated protein kinase signaling pathway

Tubeimoside I (TBMS) is a natural compound with antitumor properties. However, the detailed mechanism underlying the function of TBMS in liver cancer has not been fully elucidated. In the present study, TBMS was shown to suppress cell proliferation and induce S phase cell cycle arrest in HepG2 cells. Furthermore, TBMS treatment induced autophagy, evidenced by autophagosome accumulation, and increased the mRNA expression of Beclin 1 and microtubule-associated protein 1 light chain 3 (LC3)-I. However, flow cytometry analysis demonstrated that TBMS exerted no effect on cell apoptosis. Moreover, TBMS increased the phosphorylation of AMP-activated protein kinase (AMPK) in a concentration-dependent manner, thereby activating the AMPK signaling pathway. A specific AMPK inhibitor, compound C (CC), caused markedly suppressed TBMS-induced accumulation of LC3-II. In addition, the mRNA expression of LC3-I and Beclin 1 was also suppressed in cells treated with TBMS and CC in combination. The results of the present study provide new insights into the role of TBMS in inducing autophagy and support the potential application of TBMS for liver cancer treatment in the clinical setting.

Tubeimoside I induces accumulation of impaired autophagolysosome against cervical cancer cells by both initiating autophagy and inhibiting lysosomal function

Cervical cancer is one of the most aggressive human cancers with poor prognosis due to constant chemoresistance and repeated relapse. Tubeimoside I (TBM) has been identified as a potent antitumor agent that inhibits cancer cell proliferation by triggering apoptosis and inducing cell cycle arrest. Nevertheless, the detailed mechanism remains unclear and needs to be further elucidated, especially in cervical cancer. In this study, we found that TBM could induce proliferation inhibition and cell death in cervical cancer cells both in vitro and in vivo. Further results demonstrated that treatment with TBM could induce autophagosome accumulation, which was important to TBM against cervical cancer cells. Mechanism studies showed that TBM increased autophagosome by two pathways: First, TBM could initiate autophagy by activating AMPK that would lead to stabilization of the Beclin1-Vps34 complex via dissociating Bcl-2 from Beclin1; Second, TBM could impair lysosomal cathepsin activity and block autophagic flux, leading to accumulation of impaired autophagolysosomes. In line with this, inhibition of autophagy initiation attenuated TBM-induced cell death, whereas autophagic flux inhibition could exacerbated the cytotoxic activity of TBM in cervical cancer cells. Strikingly, as a novel lethal impaired autophagolysosome inducer, TBM might enhance the therapeutic effects of chemotherapeutic drugs towards cervical cancer, such as cisplatin and paclitaxel. Together, our study provides new insights into the molecular mechanisms of TBM in the antitumor therapy, and establishes potential applications of TBM for cervical cancer treatment in clinic.

A hybrid method for the determination of tubeimoside I in rat plasma after oral administration by LC-IT-TOF and UPLC-MS/MS

Tubeimoside I (Tub) is a triterpenoid saponin isolated from Bolbostemma paniculatum[Maxim]Franquet. A sensitive and validated method was developed to determine Tub in rat plasma. This method combined the qualitative and quantitative advantages from liquid chromatography coupled with hybrid ion trap-time of flight mass spectrometer (HPLC-DAD-IT-TOF-MS) and a triple quadrupole-linear ion trap mass spectrometer 5500 (Qtrap 5500), owing to the narrow molecular range of Qtrap 5500 relative to the molecular weight of Tub. Initially, ion detection was achieved using negative ionization mode along with full scan on IT-TOF-MS. The detected precursor and product ions of Tub with the optimal mass parameters were determined on Qtrap 5500 by an online stepped optimization strategy and operated in negative multiple reaction monitoring mode. A simple methanol precipitation was employed with saikosaponin A as internal standard. The method was validated over the range from 20 to 2000 ng/mL with a lower limit of quantification of 20 ng/mL for Tub in plasma. The developed method was successfully applied to the pharmacokinetic study of Tub in rats following oral administration. Moreover, this method has some directive significance for the determination of other drugs whose parent ions exceeding the upper detection limit in Qtrap 5500.

Terpenoid glycosides from the root's barks of Eriocoelum microspermum Radlk. ex Engl

Eight undescribed triterpenoid saponins together with a known one, and two undescribed sesquiterpene glycosides were isolated from root's barks of Eriocoelum microspermum. Their structures were elucidated by spectroscopic methods including 1D and 2D experiments in combinaison with mass spectrometry as 3-O-α-L-rhamnopyranosyl-(1 → 3)-[α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 3)-[β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 3)-[β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 4)-[α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosylhederagenin 28-O-β-D-glucopyranosyl ester, 3-O-α-L-rhamnopyranosyl-(1 → 3)-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-xylopyranosyl-(1 → 4)-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosylhederagenin, 1-O-{β-D-xylopyranosyl-(1 → 3)-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 6)}-[β-D-xylopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-(2E,6E)-farnes-1-ol, 1-O-{β-D-glucopyranosyl-(1 → 3)-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 6)}-[β-D-xylopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-(2E,6E)-farnes-1-ol. These results represent a contribution to the chemotaxonomy of the genus Eriocoelum highlighting farnesol glycosides as chemotaxonomic markers of the subfamily of Sapindoideae in the family of Sapindaceae.

Cytotoxic 16-beta-[(D-xylopyranosyl)oxy]oxohexadecanyl triterpene glycosides from a Malagasy plant, Physena sessiliflora

Brine shrimp lethality assay-guided separation of the MeOH extract of leaves of Physena sessiliflora, which is endemic to Madagascar, afforded eight triterpene glycosides, Physenoside S1-4 and 16-beta-[(d-xylopyranosyl)oxy]oxohexadecanyl homologues, Physenoside S5-8. Structural elucidation of these compounds was based on both spectroscopic analyses and chemical properties. Physenoside S7 and S8 have significant cytotoxic activities in the brine shrimp lethality assay.

[Studies on the constituents of cucurbitaceous plants]

I have an opportunity to have co-operative studies with Chinese group of Kunming Institute of Botany. Since then, I have investigated the chemical constituents of a number of Chinese plants of Araliaceae, Umbelliferae, Labiatae, Cucurbitaceae and other families. This review describes the structural elucidation of the cucurbitane, oleanane and dammarane glycosides, and their biological activities under the joint studies on cucurbitaceous plants, Bolbostemma, Hemsleya, Siraitia and Neoalsomitra species. New oleanane glycosides having novel cyclic structure were isolated from Bolbostemma paniculatum. The potent solubilizing effect of these compounds was investigated. A number of cucurbitane glycosides were isolated from Hemsleya carnosiflora, H. panacis-scandens, Siraitia grosvenorii and S. siamensis. Some of these glycosides taste sweet, bitter or tasteless. The structure-taste relationships of the glycosides of a 3-alpha-hydroxy-cucurbit-5-ene-type triterpene have been discussed. Anti-tumor-promotion effects as well as the ecdysteroid agonist and antagonist activities of these cucurbitane glycosides were investigated. New dammarane glycosides were isolated from Neoalsomitra integrifoliola.

Identification and Quantification of three Tubeimosides in Rhizoma Bolbostematis by High Performance Liquid Chromatography with Evaporative Light Scattering Detection and Electrospray Mass Spectrometric Detection

Tubeimoside I, tubeimoside II and tubeimoside III were simultaneously determined and identified by high performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC-ESI/MS), and a novel and sensitive high performance liquid chromatography - evaporative light scattering detection (HPLC-ELSD) in a 70% methanol extract of Rhizoma Bolbostematis. The chromatographic separation was performed on a Zorbax Extend C18 analytical column using gradient elution with a solution of acetonitrile and 0.5% acetic acid. The method was validated with acceptable linearities (r > 0.9992) and recoveries (98.6 to 102.4 %). The limits of detection of these three tubeimosides were as low as 0.05 μg. The intra- and inter-day precisions of the method were evaluated and were less than 3.6%. The method was successfully used to analyze 15 batches of Rhizoma Bolbostematis. The content of tubeimosides in the plant material varied from habitat to habitat confirming the necessity to control the quality of Rhizoma Bolbostematis during its preparation and application in the clinic.

Total synthesis of lobatoside E, a potent antitumor cyclic triterpene saponin

Lobatoside E, a novel and complex cyclic triterpene saponin showing potent antitumor activities, has been synthesized for the first time, employing a highly modular approach. The synthesis, starting with oleanolic acid, D-glucose, D-galactose, L-arabinose, and L-rhamnose, requires a total of 73 steps, with the longest linear sequence of 31 steps and in 1.2% overall yield.

Saponins: Properties, Applications and Processing

Saponins are a diverse group of compounds widely distributed in the plant kingdom, which are characterized by their structure containing a triterpene or steroid aglycone and one or more sugar chains. Consumer demand for natural products coupled with their physicochemical (surfactant) properties and mounting evidence on their biological activity (such as anticancer and anticholesterol activity) has led to the emergence of saponins as commercially significant compounds with expanding applications in food, cosmetics, and pharmaceutical sectors. The realization of their full commercial potential requires development of new processes/processing strategies to address the processing challenges posed by their complex nature. This review provides an update on the sources, properties, and applications of saponins with special focus on their extraction and purification. Also reviewed is the recent literature on the effect of processing on saponin structure/properties and the extraction and purification of sapogenins.

Quantitative determination of the anticancer agent tubeimoside I in rat plasma by liquid chromatography coupled with mass spectrometry

Tubeimoside I is an important component isolated from Bolbostemma paniculatum. Tubeimoside I has been demonstrated to possess many pharmacological activities, including anti-inflammatory, antitumor, and antitumor-promoting effects. The purpose of the present study was to examine in vivo pharmacokinetics and bioavailability of tubeimoside I in rats by using a liquid chromatography coupled with mass spectrometry quantitative detection method (LC/MS). The plasma samples were deproteinated, evaporated and reconstituted in 100 microl methanol prior to analysis. The separation was performed by Waters Symmetry C18 reversed-phase column (3.5 microm, 150 mm x 2.1mm, Waters Inc., USA) and a SB-C18 guard column (5 microm, 20 mm x 4.0mm). The mobile phase was a mixture of acetonitrile and water containing 5 microM NaAc (60:40, v/v). The method was validated within the concentration range 20-5000 ng/ml, and the calibration curves were linear with correlation coefficients >0.999. The lowest limit of quantitation (LLOQ) for tubeimoside I was 20 ng/ml in 0.1 ml rat plasma. The intra-assay accuracy and precision ranged from 92.4 to 104.9% and from 5.8 to 10.5%, respectively, while inter-assay accuracy and precision ranged from 94.2 to 95.0% and from 5.1 to 8.8%, respectively. The method was further applied to assess pharmacokinetics and oral bioavailability of tubeimoside I after intravenous and oral administration to rats. The oral bioavailability of tubeimoside I is only 0.23%, which indicates that tubeimoside I has poor absorption or undergoes acid-induced degradation. Practical utility of this new LC/MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration.

Tubeimoside V (1), a new cyclic bisdesmoside from tubers of Bolbostemma paniculatum, functions by inducing apoptosis in human glioblastoma U87MG cells

Malignant glioblastoma is one of the most common malignant tumors in the neurological system. Tubeimoside V (1), a new cyclic bisdesmoside from tubers of Bolbostemma paniculatum, appears to exhibit various biological activities, including antitumor effect, but the function and mechanism of this new agent on glioblastoma cells has not previously been determined. In the present study, we investigated the proliferation change of human glioblastoma U87MG cells exposured to different concentrations (0.9-14.8 microM) of Tubeimoside V (1) for a certain time. The results showed that Tubeimoside V (1) significantly suppressed U87MG cell proliferation in a time- and dose-dependent manner (IC(50) = 3.6 microM). Flow cytometric analysis of DNA in U87MG cells showed that Tubeimoside V (1) induces the prominent appearance of a sub-G1 peak in the cell cycle suggestive of apoptosis. Furthermore, U87MG cells' treatment with Tubeimoside V (1) resulted in nuclear condensation with apoptotic bodies observed by both fluorescence and electron microscopy. The result of annexin V/PI assay showed that phosphatidylserine externalization began after treatment, and then increased in the following 24h. Molecular changes explored through Western-blot staining showed Tubeimoside V (1) decreased the expression levels of Bcl-2 protein and increased the expression levels of Bax protein. The novel findings suggest that the cytotoxic actions of Tubeimoside V (1) toward U87MG cells result from the induction of cell apoptosis. Overall, our data demonstrate that Tubeimoside V (1) is an efficient apoptotic killing agent of glioblastoma cells and suggest that this mechanism may play a critical role in anti-tumor chemotherapy.

Revised chirality of the acyl group of 8'-O-(3-hydroxy-3-methylglutaryl)-8'-hydroxyabscisic acid

8'-O-(3-Hydroxy-3-methylglutaryl)-8'-hydroxyabscisic acid is a stable conjugate of the first metabolite of abscisic acid, 8'-hydroxyabscisic acid, that is spontaneously isomerized to phaseic acid. The chirality of the 3-hydroxy-3-methylglutaryl group of the conjugate was revised to S based on an HPLC analysis of the diastereomer derived from mevalonolactone obtained by reduction of the conjugate with lithium borohydride.

Steroidal saponins from the bulbs of Lilium regale and L. henryi

Two new and three known steroidal saponins were isolated from the fresh bulbs of Lilium regale and two known saponins from those of L. henryi. The structures of the new saponins were established by extensive spectral data, hydrolysis and chemical correlation as (25R)-27-O-[(S)-3-hydroxy-3-methylglutaroyl]-spirost-5 -ene-3 beta,27-diol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->3)]- beta-D-glucopyranoside and (25S)-spirost-5-ene-3 beta,17 alpha,27-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->2)-O- beta-D-glucopyranosyl-(1-->4)]-beta-D-glucopyranoside. Inhibitory activity of the saponins on cyclic AMP phosphodiesterase was evaluated.

Two triterpenoid saponins from Pterocephalus bretschneidri

Two new triterpenoid saponins, named bretschnosides A and B, were isolated from the roots of Pterocephalus bretschneidri. On the basis of chemical degradation and spectroscopic evidence, the structures of bretschnosides A and B were shown to be 3-O-alpha-L-rhamnopyranosyl(1-->3)- beta-D-xylopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->2)-beta-D- xylopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside 4 and 3-O-alpha-D-glucopyranosyl(1-->3)-beta-D-xylopyranosyl(1-->3)-alpha-L- rhamnopyranosyl(1-->2)-beta-D-xylopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside 6, respectively.

Steroidal saponins from the bulbs of Allium schubertii

Phytochemical examination of the fresh bulbs of Allium schubertii led to the isolation of four new steroidal saponins together with a known saponin. The structures of the new saponins were established by spectroscopic data, hydrolysis and chemical correlation as (25R and S)-5 alpha-spirostan-2 alpha,3 beta,6 beta-triol 3-O-beta-D-glucopyranosyl-(1-->2)-O-[4-O-benzoyl-beta-D-xylopyranosyl- (1-->3)]-O-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside, (25R and S)-5 alpha-spirostan-2 alpha,3 beta,6 beta-triol 3-O-beta-D-glucopyranosyl-(1-->2)-O-[3-O-benzoyl-beta-D-xylopyranosyl- (1-->3)]-O-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside, (25R and S)-5 alpha-spirostan-2 alpha,3 beta,6 beta-triol 3-O-beta-D-glucopyranosyl-(1-->2)-O-[4-O-(3S)-3-hydroxy-3-methylgluta royl- beta-D-xylopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->4)-beta-D- galactopyranoside and 26-O-beta-D-glucopyranosyl-(25R and S)-5 alpha-furostan-2 alpha,3 beta,6 beta,22 zeta,26-pentol 3-O-beta-D-glucopyranosyl-(1-->2)-O-[beta-D-xylopyranosyl-(1-->3)]-O-bet a- D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside, respectively.