Paolo Luciano

Aplidiasterols A and B, two new cytotoxic 9,11-secosterols from the Mediterranean ascidian Aplidium conicum.

Two novel 9,11-secosterols, aplidiasterols A (3beta,6beta,11-trihydroxy-9,11-seco-5alpha-cholest-7-en-9-one, 1) and B (3beta,5alpha,6beta,11-tetrahydroxy-9,11-secocholest-7-en-9-one, 2), along with the known secosterols 3 and 4, were isolated from the Mediterranean ascidian Aplidium conicum and their structures were determined by spectroscopic data. Aplidiasterols A and B were found to be cytotoxic against rat glioma (C6) and murine monocyte/macrophage (J774) tumor cells in vitro. Compounds 1-4 represent the first example of secosterols isolated from tunicates.

Polyaxibetaine, an amino acid derivative from the marine sponge Axinella polypoides.

A new pyridinium derivative, polyaxibetaine (3), has been isolated from the marine sponge Axinella polypoides, together with two known modified amino acids, 1 and 2. The planar structure of compound 3 has been elucidated by spectroscopic methods; definition of the absolute configuration of compounds 1-3 has been carried out through ECD studies.

Synthesis of structurally simplified analogues of aplidinone A, a pro-apoptotic marine thiazinoquinone

The synthesis of analogues of aplidinone A (7), a prenylated quinone isolated from the Mediterranean ascidian Aplidium conicum, has been performed. This work not only allowed confirming the structural assignment of aplidinone A, previously made with the support of GIAO shielding calculations, but, above all, made a series of structurally related quinone derivatives (compounds 8-13 and the natural metabolite) available for a screening in vitro for cytotoxic and pro-apoptotic activity and for SAR studies. The study evidenced one of the synthetic analogues (11) as a potent cytotoxic and pro-apoptotic agent against several tumor cell lines which also inhibits the TNFalpha-induced NF-kappaB activation in a human leukemia T cell line. This exemplifies the potential of a natural product to qualify as lead structure for medicinal chemistry campaigns, affording simplified analogues with better bioactivity and easier to synthesize.

Stereostructure Assignment of Medium-Sized Rings through an NMR−Computational Combined Approach. Application to the New Germacranes Ketopelenolides C and D

The new germacrane derivatives ketopelenolides C and D have been isolated from great mugwort (Artemisia arborescens). Their stereostructure elucidation exemplifies some of the most common pitfalls facing the configurational assignment of medium-sized polyfunctionalized compounds. It was established through a combined strategy including chemical derivatization, NMR data analysis, molecular modeling, and quantum-mechanical calculations including a comparison between experimental 13C NMR data and a Boltzmann-weighted average of DFT-calculated 13C NMR chemical shifts.

Zorrimidazolone, a Bioactive Alkaloid from the Non-Indigenous Mediterranean Stolidobranch Polyandrocarpa zorritensis

Chemical analysis of the Mediterranean ascidian Polyandrocarpa zorritensis (Van Name 1931) resulted in the isolation of a series of molecules including two monoindole alkaloids, 3-indolylglyoxylic acid (3) and its methyl ester (4), 4-hydroxy-3-methoxyphenylglyoxylic acid methyl ester (1) and a new alkaloid we named zorrimidazolone (2). The structure of the novel compound 2 has been elucidated by spectroscopic analysis and bioactivity of all compounds has been investigated. Zorrimidazolone (2) showed a modest cytotoxic activity against C6 rat glioma cell line.

Turmeric Sesquiterpenoids: Expeditious Resolution, Comparative Bioactivity, and a New Bicyclic Turmeronoid.

An expeditious strategy to resolve turmerone, the lipophilic anti-inflammatory principle of turmeric (Curcuma longa), into its individual bisabolane constituents (ar-, α-, and β-turmerones, 2-4, respectively) was developed. The comparative evaluation of these compounds against a series of anti-inflammatory targets (NF-κB, STAT3, Nrf2, HIF-1α) evidenced surprising differences, providing a possible explanation for the contrasting data on the activity of turmeric oil. Differences were also evidenced in the profile of more polar bisabolanes between the Indian and the Javanese samples used to obtain turmerone, and a novel hydroxylated bicyclobisabolane ketol (bicycloturmeronol, 8) was obtained from a Javanese sample of turmeric. Taken together, these data support the view that bisabolane sesquiterpenes represent an important taxonomic marker for turmeric and an interesting class of anti-inflammatory agents, whose strict structure-activity relationships are worth a systematic evaluation.

Aplisulfamines, New Sulfoxide-Containing Metabolites from an Aplidium Tunicate: Absolute Stereochemistry at Chiral Sulfur and Carbon Atoms Assigned Through an Original Combination of Spectroscopic and Computational Methods

Two new sulfoxide-containing metabolites, aplisulfamines A (1) and B (2), have been isolated from an Aplidium sp. collected in the Bay of Naples. Their planar structure and geometry of a double bond were readily determined by using standard methods, mainly NMR spectroscopy. An original approach was used to assign the absolute configuration at the three contiguous chiral centers present in the structures of both aplisulfamines, two at carbon and one at sulfur. This involved Electronic Circular Dichroism (ECD) studies, J-based configuration analysis and Density Functional Theory (DFT) calculations and represents an interesting integration of modern techniques in stereoanalysis, which could contribute to the enhancement of theoretical protocols recently applied to solve stereochemical aspects in structure elucidation.

PPAR Modulating Polyketides from a Chinese Plakortis simplex and Clues on the Origin of Their Chemodiversity.

Fifteen polyketides, including the first hydroxylated plakortone (12) and plakdiepoxide (15), the first polyketide to embed a vicinal diepoxide, have been isolated from the Chinese sponge Plakortis simplex. The structures of the new metabolites were elucidated by analysis of spectroscopic data, Moshers derivatization, and DFT computational calculations. The reactivity of the major endoperoxide of this sponge was investigated, suggesting that furan, furanylidene, and plakilactone derivatives, well-known classes of natural products, could actually be chemical degradation products. Plakdiepoxide is a potent and selective modulator of peroxisome proliferator-activated receptor (PPAR)-γ, while the diunsaturated C12 fatty acid monotriajaponide (13) activates both PPAR-α and PPAR-γ, a dual activity of potential great importance for the treatment of metabolic disorders.

Structure and Configuration of Phosphoeleganin, a Protein Tyrosine Phosphatase 1B Inhibitor from the Mediterranean Ascidian Sidnyum elegans

A new phosphorylated polyketide, phosphoeleganin (1), has been isolated from the Mediterranean ascidian Sidnyum elegans. Its structure and configuration have been determined by extensive use of 2D NMR and microscale chemical degradation and/or derivatization. Phosphoeleganin (1) inhibited the protein tyrosine phosphatase 1B (PTP1B) activity.

Further Investigation of the Mediterranean Sponge Axinella polypoides: Isolation of a New Cyclonucleoside and a New Betaine

An exhaustive exploration into the metabolic content of the Mediterranean sponge Axinella-polypoides resulted in the isolation of the new betaine 5 and the new cyclonucleoside 8. The structures of the new metabolites were elucidated by spectroscopic methods assisted by computational methods. The analysis also provided evidence that the sponge does not elaborate pyrrole-imidazole alkaloids (PIAs) but, interestingly, it was shown to contain two already known cyclodipeptides, compounds 9 (verpacamide A) and 10.