Jorge A. Palermo

STORNIAMIDES A-D : ALKALOIDS FROM A PATAGONIAN SPONGE CLIONA SP.

Abstract Four novel peptide alkaloids, storniamides A-D ( 1 – 4 ) were isolated from a sponge Cliona sp. collected near San Antonio Oeste, Rio Negro, Argentina, and their structures established by spectroscopic methods.

Chondriamides A and B, new indolic metabolites from the red alga Chondria sp.

Abstract Chondriamides A and B, two cytotoxic bis-indolic amides were isolated from a red alga Chondria Sp. and their structures established from spectroscopic data.

Identification of two meridianins from the crude extract of the tunicate Aplidium meridianum by tandem mass spectrometry.

As part of the development of an analytical technique for the detection of meridianins and related compounds in biological fluids, a crude extract of the tunicate Aplidium meridianum was analysed using neutral loss tandem mass spectrometry. The 41 u neutral loss-EI(+) mass spectrum showed molecular ions corresponding to two previously undetected alkaloids. We report herein the isolation and structure elucidation of these alkaloids, meridianins F and G. †Dedicated to the memory of Dr Alicia M. Seldes, Founder and Leader of the research group on Marine Natural Products at the Department of Organic Chemistry, FCEN-UBA.

Carotenoids from three red algae of the corallinaceae

Abstract The carotenoid composition of the red algae Corallina officinalis , Corallina elongata and Jania sp. were analysed. The same eight compounds were isolated and identified from the three species: β-carotene, zeaxanthin, fucoxanthin, 9′- cis -fucoxanthin, fucoxanthinol,9′- cis -fucoxanthinol and the epimeric mutatoxanthins. The latter two components are described for the first time as natural products from the marine environment. The results allowed us to infer that Corallinaceae are able to produce de novo allenic and epoxy carotenoids, contrary to the general supposition that their presence in the algae was due to colonizing organisms.

Synthesis and cytotoxic activity evaluation of dihydrocucurbitacin B and cucurbitacin B derivatives

Two cucurbitacins, dihydrocucurbitacin B (1) and cucurbitacin B (2), which can be obtained in large amounts from the roots of Wilbrandia ebracteata and from the fruits of Luffa operculata, respectively, were used as starting materials for the preparation of a library of 29 semi-synthetic derivatives. The structural changes that were performed include the removal, modification or permutation of functional groups in rings A and B as well as in the side chain. All new semisynthetic compounds, as well as 1 and 2, were tested in vitro for their cytotoxic effects on non-small-cell lung cancer cells (A549 cells). Some of these compound displayed potent to moderate activity against A549 tumor cells, especially those cucurbitacin B derivatives which were modified at ring A.

Antiproliferative terpenoids and alkaloids from the roots of Maytenus vitis-idaea and Maytenus spinosa

Investigation of the organic extracts of the roots of Maytenus vitis-idaea and Maytenus spinosa, collected in the province of Salta, Argentina, led to isolation of eighteen compounds belonging to several classes. From M. vitis-idaea, eight methylenequinone celastroids (1-8) were isolated, four of which (4-7) were hitherto unknown. Additionally, from M. spinosa, two known celastroids, a known celastroid dimer (9), three pentacyclic triterpenoids (10-12) and six β-dihydroagarofuran sesquiterpenoid alkaloids (13-18) were identified. Compounds 4-7 were active against six solid tumor cell lines at micromolar concentrations.

Antiparasitic hybrids of Cinchona alkaloids and bile acids.

A series of 16 hybrids of Cinchona alkaloids and bile acids (4a-h, 5a-h) was prepared by means of a Barton-Zard decarboxylation reaction. Quinine, quinidine, cinchonine and cinchonidine were functionalized at position C-2 of the quinoline nucleus by radical attack of a norcholane substituent. The newly synthesized hybrids were evaluated in vitro for their antitrypanosomal, antileishmanial and antiplasmodial activities, along with their cytotoxicity against WI38, a normal human fibroblast cell line. Seven compounds (4d, 4f, 4h, 5b, 5d, 5f, 5h) showed promising trypanocidal activity with IC₅₀ values in the same range as the commercial drug suramine. Moreover all the 16 hybrids showed antiplasmodial activity (IC₅₀ ≤ 6 μg/ml), particularly those containing a nor-chenodeoxycholane moiety (4b, 4d, 4f, 4h, 5b, 5d, 5f, 5h) with IC₅₀ values comparable to those of the natural alkaloids, and selectivity indices in the range of 5.6-15.7.

Synthesis of steroidal quinones and hydroquinones from bile acids by Barton radical decarboxylation and benzoquinone addition. Studies on their cytotoxic and antifungal activities.

Twelve new hydroquinones and quinones (4a-c to 7a-c) derived from free or peracetylated bile acids were prepared by a Barton decarboxylation reaction, with subsequent trapping of the resulting free radical by benzoquinone. All new compounds were completely characterized by 2D NMR techniques and screened for antifungal and cytotoxic activity. One of the new hydroquinones (7b) showed promising results against the human pancreatic ductal carcinoma cell line PANC1, with similar cytotoxic activity as the commercial chemotherapy drug doxorubicin.

New C-secosteroids from the gorgonian Tripalea clavaria

Seven new C-secosteroids were isolated from the gorgonian Tripalea clavaria collected from the South Atlantic. These compounds have a Delta(5), 9,11-secosteroid nucleus together with a 22S hydroxyl group. The absolute configuration of the 22-hydroxyl group was determined with the help of COSY spectra of the Mosher esters of the compounds.

Dolabellane Diterpenoids from the South Atlantic Gorgonian Convexella magelhaenica.

Two new dolabellane diterpenoids (1 and 2) were isolated from a small sample of the deep water gorgonian octocoral Convexella magelhaenica collected as a nontarget by-catch by dredging (-93 m) in commercial Patagonian scallop fishing grounds in the South Atlantic. The structures of the new compounds, which are major metabolites in the extract, were established by spectroscopic techniques and chemical transformations. Both compounds were cytotoxic against a human pancreatic adenocarcinoma cell line at micromolar concentrations.