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Two new triterpene glycosides, namely holothurin A3 (1) and A4 (2) were isolated from the methanol extract of the sea cucumber, Holothuria scabra, with their structures elucidated from the spectroscopic evidence (1D NMR, 2D NMR, ESI-MS and HRESI-MS). Compounds 1 and 2 were found to be strongly cytotoxic to both cancer cell lines, KB and Hep-G2, with 50% inhibitory concentrations (IC50) of 0.87 and 0.32 microg/mL (for compound 1) and of 1.12 and 0.57 microg/mL (for compound 2), respectively.

Essential oils were extracted from the culm and leaf of Cymbopogon citratus collected from different regions of Vietnam and analyzed using GC/MS. The results showed that citral is the major component accounting for 61.20%–76.46% of the essential oils. The citral content was higher in the essential oil obtained from the leaf than in that from the culm of lemongrass in all regions. In particular, camphene, valerianol, and epi-α-muurolol can be used to differentiate essential oils originating from leaves versus culms. The cytotoxic effects of the essential oils on various lung cancer cell lines were evaluated in the present study. All essential oils exhibited cytotoxicity in the tested cells. The Ha Loc leaf essential oil (HLL) exhibited the most potent effects on A549 and H1975 cells, with IC50 values of 1.73 ± 0.37 and 4.01 ± 0.30 μg/mL, respectively. The Hy Cuong leaf essential oil (HCL) showed the strongest effect on H1299 cells, with an IC50 value of 2.45 ± 0.21 μg/mL. The Kim Duc culm (KDC) essential oil exerted the strongest cytotoxic effects against H1650 cells, with an IC50 value of 4.86 ± 0.29 μg/mL. The HLL induced apoptosis and cycle arrest in A549 cells according to flow cytometric analysis and fluorescent nuclear staining assays. The western blot analysis indicated that HLL induced the apoptotic effect by altering the regulating proteins of the apoptosis process such as caspase-3, Bcl-2, and Bax. The data strongly suggested that the intrinsic pathway may play an important role in the apoptotic effects of HLL.

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MSC: 34C12 60H10 92D25Keywords: Kolmogorov systems of competitive type Telegraph noise Stationary distribution ω-limit set This paper studies the dynamics of Kolmogorov systems of competitive type under the telegraph noise. The telegraph noise switches at random two Kolmogorov competition-type deterministic models. The aim of this work is to describe the omega-limit set of the system and investigates properties of stationary density.

NotesCleistocalyx operculatus (ROXB.) MERR. et PERRY (Myrtaceae) is a large green tree that grows in rural areas of North Vietnam where it is commonly called Voi. The flower buds (name as Nu Voi) and leaves (La Voi) have been used to make a beverage since ancient times.1) It is also a wellknown medicinal plant whose buds are commonly used as an ingredient for tonic drinks in Southern China.2) The water extract of C. operculatus buds has been shown to increase the contractility and decrease the frequency of contraction in an isolated rat heart perfusion system.3) It showed strong protective effects on lipid peroxidation in rat liver microsomes, and the H 2 O 2 -induced trauma of rat pheochromocytima (PC12) cells. 4) C. operculatus extract showed inhibitory activity against the a-glucosidase, rat-intestinal maltase, and sucrase activities. It is also considered a promising material for preventing and treating diabetes. 5) Previous phytochemical attention characterized the oleanane-type triterpenes, 6,7) and flavonoids.2) Analysis of its leaf oil by gas chromatography (GC) and chromatography/mass spectrometry (GC/MS) has also been reported. 8) Chalcone compounds from this plant possess antioxidant and anticancer activities. [9][10][11] In this report, we describe the isolation and structural determination of four new flavonoids (1-4), and evaluate their DPPH radical scavenging activity. Results and DiscussionThe MeOH extract of the buds of C. operculatus was partitioned into hexane-, EtOAc-, and BuOH-soluble fractions. Chromatographic purification of the EtOAc-soluble fraction led to the isolation of four compounds (1-4) (Fig. 1).Compound 1 was isolated as a yellow amorphous powder. In the positive ion mode, electrospray ionization mass spectrometry (ESI-MS), a quasimolecular ion peak at m/z 329 [MϩH] ϩ was observed, and high-resolution ESI-MS (HR-ESI-MS) analysis indicated an ion peak at 329.1813 which corresponded to the molecular formula, C 18 H 16 O 6 . The infrared (IR) absorptions at 3452, 2873 and 2758 cm Ϫ1 showed the presence of hydroxy and aldehyde groups. The 1 H nuclear magnetic resonance (NMR) spectrum of 1 indicated the presence of methoxy group at d 3.82 (3H, s), aldehyde group at d 10.41 (1H, s), and methyl group at d 2.04 (3H, s). Proton signals were also observed at d 7.54 (2H, dd, Jϭ8.5, 2.0 Hz, H-2, 6) and d 6.94 (2H, dd, Jϭ8.5, 1.8 Hz, H-3, 5) and assigned to 4-substituted phenyl in the B ring of chalcone.12) An AB spin system with Jϭ15.8 Hz at d 7.73 and 7.78 indicated the presence of protons of an a,b-unsaturated ketone moiety.2) The 13 C-NMR and distortionless enhancement by polarization transfer (DEPT) spectrum of 1 showed 18 signals, including three oxygenated aromatic carbons at d 165.7 (C-2Ј), 169.8 (C-6Ј) and 160.7 (C-4), one carbonyl carbon at d 193.8 (CϭO), one aldehyde carbon at d 191.7 (3Ј-CHO), one methyl carbon at d 10.6 (5Ј-CH 3 ), and four aromatic carbons at d 130.2 (C-2, 6) and 118.3 (C-3, 5). The 1 H-and 13 C-NMR spectra (Table 1) were very similar to those of 3Ј-formyl-4Ј,...

In this paper we study the Kernack -MacKendrick model under telegraph noise. The telegraph noise switches at random between two SIRS models. We give out conditions for the persistence of the disease and the stability of a disease free equilibrium. We show that the asymptotic behavior highly depends on the value of a threshold λ which is calculated from the intensities of switching between environmental states, the total size of the population as well as the parameters of both SIRS systems. According to the value of λ, the system can globally tend towards an endemic case or a disease free case. The aim of this work is also to describe completely the omega-limit set of all positive solutions to the model. Moreover, the attraction of the omega-limit set and the stationary distribution of solutions will be pointed out.1991 Mathematics Subject Classification. 34C12, 60H10, 92D30.

Three bisdesmosidic saponins 3-O-[β-D-glucopyranosyl-(1→4)-β-D-glucuronopyranosyl] oleanolic acid 28-O-β-D-glucopyranosyl ester (1), polyscioside D (2), and 3-O-{β-D-glucopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-β-D-glucuronopyranosyl}oleanolic acid 28-O-β-D-glucopyranosyl-(1→2)-β-D-galactopyranosyl ester (3) were isolated from a methanol extract ofPolyscias fruticosa(L.) Harms leaves. Compound1was obtained as a main constituent and compound3was reported for the first time and named as polyscioside I. Saponin1inhibited porcine pancreasα-amylase and yeastα-glucosidase activities while2and3were inactive. Synergistic inhibitory effect onα-amylase was observed from the combination of low concentrations of1and acarbose. The findings suggest the use ofP. fruticosaand its major saponin1for the prevention and treatment of diabetes and its complications.