Do Cong Thung

Cytotoxic and antioxidant activities of diterpenes and sterols from the Vietnamese soft coral Lobophytum compactum.

Two new diterpenes, lobocompactols A (1) and B (2), and five known compounds (3-7) were isolated from the methanol extract of the soft coral Lobophytum compactum using combined chromatographic methods and identified based on NMR and MS data. Each compound was evaluated for cytotoxic activity against A549 (lung) and HL-60 (acute promyelocytic leukemia) human cancer cell lines. Among them, compound 5 exhibited strong cytotoxic activity against the A549 cell line with an IC(50) of 4.97 ± 0.06 μM. Compounds 3, 4, and 7 showed moderate activity with IC(50) values of 23.03 ± 0.76, 31.13 ± 0.08, and 36.45 ± 0.01 μM, respectively. The cytotoxicity of 5 on the A549 cells was comparable to that of the positive control, mitoxantrone (MX). All compounds exhibited moderate cytotoxicity against the HL-60 cell line, with IC(50) values ranging from 17.80 ± 1.43 to 59.06 ± 2.31 μM. Their antioxidant activity was also measured using oxygen radical absorbance capacity method, compounds 1 and 2 exhibiting moderate peroxyl radical scavenging activity of 1.4 and 1.3 μM Trolox equivalents, respectively, at a concentration of 5 μM.

Cytotoxic triterpene saponins from Cercodemas anceps

Seven holostane-type triterpene saponins (1-7), including five new compounds namely cercodemasoides A-E (2-6), were isolated from the sea cucumber Cercodemas anceps. Their structures were elucidated on the basis of spectroscopic evidence including HR ESI MS, ESI MS/MS, 1D and 2D NMR. The cytotoxic effects of isolated compounds were evaluated by SRB method on five human cancer cell lines including Hep-G2 (hepatoma cancer), KB (epidermoid carcinoma), LNCaP (prostate cancer), MCF7 (breast cancer), and SK-Mel2 (melanoma). Compounds 1-7 showed potent cytotoxicity on five tested cancer cell lines with IC50 values ranging from 0.03 ± 0.01 to 7.36 ± 0.46 μM. With respect to the potent cytotoxicity of the isolated saponins, further studies are required to confirm efficacy in vivo and the mechanism of cytotoxic effects.

Cytotoxic triterpene diglycosides from the sea cucumber Stichopus horrens

Using various chromatographic separation techniques, eight triterpene diglycosides (1-8), including four new compounds namely stichorrenosides A-D (1-4), were isolated from a methanol extract of the Vietnamese sea cucumber S. horrens. Their structures were elucidated based on spectroscopic analyses, including HR ESI MS, 1D and 2D NMR. Their in vitro cytotoxic activity against five human cancer cell lines, Hep-G2 (hepatoma cancer), KB (epidermoid carcinoma), LNCaP (prostate cancer), MCF7 (breast cancer), and SK-Mel2 (melanoma), was evaluated using SRB methods. Stichorrenoside D (4), stichoposide A (5), and 3β-O-[β-d-xylopyranosyl-(1→2)-β-d-xylopyranosyl]-23S-acetoxyholost-7-ene (7) showed strong cytotoxicity on all five tested cancer cell lines, whereas significant effect was observed for stichorrenoside C (3) and stichoposide B (6).

Asterosaponins and glycosylated polyhydroxysteroids from the starfish Culcita novaeguineae and their cytotoxic activities

Using combined chromatographic methods, two asterosaponins (compounds 1 and 2), including a new compound novaeguinoside E (compound 1), and six glycosylated polyhydroxysteroids (compounds 3–8) were isolated from a methanol extract of the starfish Culcita novaeguineae. Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H–1H COSY, ROESY, and HRESI-MS) and by comparison with the literature values. The new compound 1 represents the third example of asterosaponins containing the 5α-cholesta-9(1l)-en-3β,6α,20,22-tetraol aglycone. Among isolated compounds, 4–7 exhibited moderate to weak cytotoxic activities against five human cancer cell lines such as Hep-G2 (hepatoma), KB (epidermoid carcinoma), LNCaP (prostate cancer), MCF7 (breast cancer), and SK-Mel2 (melanoma).

Steroid constituents from the soft coral Sinularia microspiculata

Abstract A methanol extract of the soft coral Sinularia microspiculata revealed five sterols, including two new compounds. Using combined chromatographic and spectroscopic experiments, the new compounds were found to be 7-oxogorgosterol (1) and 16α-hydroxysarcosterol (2). Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY, and FT-ICR-MS) and by comparing obtained results to the values indicated in previous studies. Among the isolated compounds, 3 showed weak cytotoxic effects against HL-60 (IC50  =  89.02  ±  9.93 μM) cell line, whereas 5 was weakly active against HL-60 (IC50  =  82.80  ±  13.65 μM) and SK-Mel2 (IC50  =  72.32  ±  1.30 μM) cell lines.

Steroid Constituents from the Soft Coral Sinularia nanolobata

Six steroids (1-6), including the two new compounds 3β,4α-dihydroxyergosta-5,24(28)-diene (1) and 24(S),28-epoxyergost-5-ene-3β,4α-diol (2), were isolated from the methanol extract of the Vietnamese soft coral Sinularia nanolobata. Their structures were elucidated by spectroscopic methods including one and two dimensional (1D- and 2D)-NMR, Fourier transform ion cyclotron resonance (FT-ICR)-MS, and circular dichroism (CD). Compound 2 exhibited moderate cytotoxicity against the acute leukemia (HL-60) cell line with IC50 value of 33.53±4.25 µM and weak effect on the hepatoma cancer (HepG2) and colon adenocarcinoma (SW480) cell lines with IC50 values of 64.35±7.00 and 71.02±4.00 µM, respectively.

Cytotoxic Steroids from the Vietnamese Soft Coral Sinularia conferta

Twelve steroids, including five new compounds 1-5, were isolated and structurally elucidated from a methanol extract of the Vietnamese soft coral Sinularia conferta. Their cytotoxic effects against three human cancer cell lines, lung carcinoma (A-549), cervical adenocarcinoma (HeLa), and pancreatic epithelioid carcinoma (PANC-1), were evaluated using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assays. Among isolated compounds, 10 exhibited potent cytotoxic effects on all three tested cell lines with IC50 values of 3.64±0.18, 19.34±0.42, and 1.78±0.69 µM, respectively.

1)H and (13)C NMR assignments of sesquiterpenes from Dysidea fragilis.

Sesquiterpenes have been reported as components of the genus Dysidea (Dysideidae). Many chemical investigations have been focused on the marine sponge Dysidea fragilis. The constituents of D. fragilis were identified as sesquiterpenes, steroids and diketopiperazines. They exhibited various biological activities such as anti-inflammatory and cytotoxic activities. Previously, series of new sesquiterpenes were reported from the Vietnamese sponge D. cinerea by our group. In continuing research on bioactive compounds from genus Dysidea, three new and two known sesquiterpenes were isolated from the sponge D. fragilis. Herein, we report the isolation and structure elucidation of these compounds.

Triterpene tetraglycosides from the sea cucumber Stichopus horrens

Abstract Using various chromatographic separations, three triterpene tetraglycosides (1–3), including one new compound, namely stichorrenoside E (1) along with thelenotoside B (2) and deacetyl thelenotoside B (3), were isolated from the MeOH extract of the Vietnamese sea cucumber Stichopus horrens. Their structures were confirmed by spectroscopic experiments, such as 1D and 2D NMR and HR-ESI-MS. Deacetylated thelenotoside B (3) is firstly isolated as a natural product. Among these compounds, thelenotoside B (2) showed strong cytotoxicities against five human cancer cell lines as HepG2, KB, LNCaP, MCF7 and SK-Mel2 with the IC50 values from 0.95 ± 0.08 to 1.90 ± 0.13 μM, whereas stichorrenoside E (1) and deacetyl thelenotoside B (3) exhibited significant activities with the IC50 values from 6.87 ± 0.25 to 11.62 ± 1.05 μM.

Sesquiterpene constituents from the soft coral Sinularia nanolobata

Abstract Using various chromatographic separations, four sesquiterpenes (1–4), including two new compounds, nanolobatols A and B (1 and 2), were isolated from the Vietnamese soft coral Sinularia nanolobata. Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H–1H COSY, NOESY and FT-ICR-MS) and by comparison with the literature values. The cytotoxic activity of isolated compounds against a panel of eight human cancer cell lines was also evaluated.