Luciano Barboni

Recent developments on the chemistry of aliphatic nitro compounds under aqueous medium

Aliphatic nitro derivatives represent an important class of useful molecules in organic synthesis. The versatility of these compounds is largely due to their easy availability and transformation into a variety of diverse functionalities. Moreover, aliphatic nitro compounds are very important building blocks (both as nucleophiles or as electrophiles) for the generation of new carbon–carbon bonds, mainly via nitroaldol-Henry reactions, Michael reactions and Diels–Alder cycloadditions. Usually, organic solvents are believed to be necessary for achieving the best efficiency in the reactions of aliphatic nitro compounds and, only recently, it has been shown that these reactions are also very efficient using water as reaction medium. Such progress in the chemistry of aliphatic nitro compounds is particularly attractive to industry since the replacement of toxic solvents still remains a crucial (and expensive) challenge. Thus, this report is focused on the chemistry of aliphatic nitro derivatives performed in aqueous media.

Taxanes from the needles of Taxus wallichiana

Abstract Besides known compounds, the needles of T. wallichiana gave five new taxanes, whose constitution, stereochemistry and conformation were established

Dimeric antioxidant and cytotoxic triterpenoid saponins from Terminalia ivorensis A. Chev.

Three saponins, including two dimeric triterpenoid glucosides possessing an unusual skeleton, ivorenosides A and B, and a monomeric triterpenoid saponin (ivorenoside C), together with the known sericoside, were isolated from the bark of Terminalia ivorensis. Their structures were established on the basis of 1D and 2D NMR data, chemical methods and tandem MS-MS spectrometry as a dimer of β-D-glucopyranosyl-18,19-seco-2α,3β,19,19,24-pentahydroxyolean-12-en-28-oate and β-D-glucopyranosyl-2α,3β,19α,24-tetrahydroxyolean-12-en-28-oate (ivorenoside A, 1), a dimer of β-D-glucopyranosyl-18,19-seco-24-carboxyl-2α,3β,19,19-tetrahydroxyolean-12-en-28-oate and β-D-glucopyranosyl-2α,3β,19α,24-tetrahydroxyolean-12-en-28-oate (ivorenoside B, 2) and β-D-glucopyranosyl-2α,3β,19β,24-tetrahydroxyolean-11-oxo-olean-12-en-28-oate (ivorenoside C, 3). Ivorenosides A and B are the first examples in nature of dimeric triterpenoid saponins with a 18,19-seco E ring of one of the two units. These isolated compounds were evaluated for their antioxidant properties and further for their cytotoxic activity against four human cancer cell lines. Ivorenoside B and C exhibited scavenging activity against DPPH and ABTS(+) radicals with IC(50) values comparable with that of the standard drug Trolox and ivorenoside A showed antiproliferative activity against MDA-MB-231 and HCT116 human cancer cell lines with IC(50) values of 3.96 and 3.43 μM, respectively.

Rheediinosides A and B, two antiproliferative and antioxidant triterpene saponins from Entada rheedii

Two triterpenoid saponins have been isolated from the seed kernels of Entada rheedii. Their structures have been established using 1D- and 2D-NMR and mass spectrometry as 3-O-beta-D-xylopyranosyl-(1-->3)-O-alpha-l-arabinopyranosyl-(1-->6)-2-acetylamino-2-deoxy-beta-D-glucopyranosylentagenic acid 28-O-beta-apiofuranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->2)-beta-D-glucopyranoside (Rheediinoside A, 1) and 3-O-beta-D-glucopyranosyl-(1-->3)-O-[beta-D-xylopyranosyl-(1-->3)-alpha-l-arabinopyranosyl-(1-->6)]-2-acetylamino-2-deoxy-beta-D-glucopyranosylentagenic acid 28-O-beta-apiofuranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->2)-beta-D-glucopyranoside (Rheediinoside B, 2). Compounds 1 and 2 were tested for their antiproliferative activity against T98G, A431, PC3 and B16-F1 cell lines, and further for their antioxidant properties. Moderate cytotoxic potency and antioxidant properties were found for these compounds whereas Rheediinoside B was in all assays more active than Rheediinoside A.

Nitroalkanes as new, ideal precursors for the synthesis of benzene derivatives

Nitroalkanes have emerged, in the past few years, as powerful acyclic building blocks to synthesize polyfunctionalized benzene derivatives, avoiding any serious regiochemical ambiguities due to the activating/deactivating and orienting effects of the substituents. Many of these procedures are realized in a one-pot process or a few-step sequence. This feature article describes recent results, mainly from our group, in this field.

In vitro biological activity of essential oils and isolated furanosesquiterpenes from the neglected vegetable Smyrnium olusatrum L. (Apiaceae)

Smyrnium olusatrum, better known as Alexanders or wild celery, is a biennal herb used in cuisine for many centuries by Romans in many dishes, where it has now been replaced by celery. In order to provide additional evidences so that this forgotten vegetable can be reconsidered in the human diet, as well as in pharmaceutics, the essential oils obtained from different parts and its main isolated furanosesquiterpenes were in vitro biologically assayed for antiproliferative activity on human tumor cell lines by MTT assay, for antioxidant potential by DPPH, ABTS and FRAP assays, and for antimicrobial activity by the agar disc diffusion method. The essential oils showed cytotoxic effects on tested human tumor cell lines, related to the furanosesquiterpenoid content; the IC(50) values on colon carcinoma, glioblastoma, and breast adenocarcinoma cells were 8.51, 13.35, and 14.81 μg/ml, respectively. Isofuranodiene and 1β-acetoxyfuranoeudesm-4(15)-ene resulted the most active constituents. The essential oils possessed also radical scavenging activity.

Volatile oil from striped African pepper (Xylopia parviflora, Annonaceae) possesses notable chemopreventive, anti-inflammatory and antimicrobial potential

Fruits of Xylopia parviflora, well known as striped African pepper, are sold in the Cameroonian markets as a flavouring ingredient to make traditional soups. The essential oil hydrodistilled from fruits was analysed for in vitro biological activities, namely cytotoxic, anti-inflammatory, antimicrobial and antioxidant, by MTT, nitric oxide inhibitory assay, agar disc diffusion method, and DPPH and ABTS assays. The essential oil composition, analysed by GC and GC-MS, was dominated by monoterpene hydrocarbons (50.0%) responsible for the pepper odour, such as β-pinene (34.0%) and α-pinene (10.3%). The oil induced a strong inhibitory effect on tumour cells MDA-MB 231 and HCT116, with inhibition values close to those of cisplatin. A dose-dependent decrease in NO production was noted in RAW 264.7 macrophages treated with the oil, revealing a promising anti-inflammatory potential. The essential oil showed a measurable antimicrobial activity against all the species tested, while the radical scavenging activity was low.

Wild celery (Smyrnium olusatrum L.) oil and isofuranodiene induce apoptosis in human colon carcinoma cells

Smyrnium olusatrum (Apiaceae), well known as wild celery, is a biennal celery-scented plant used for many centuries as a vegetable, then abandoned after the introduction of celery. In the present work, the essential oil obtained from inflorescences and the amounts of its main constituents isofuranodiene, curzerene and germacrone were analyzed by GC as well as by HPLC because of their degradation (Cope rearrangement) occurring at high temperatures. The oil and the main constituents were assayed for cytotoxic activity on the human colon cancer cell line (HCT116) by MTT assay. Flower oil and isofuranodiene showed noteworthy activity on tumor cells with IC50 of 10.71 and 15.06 μg/ml, respectively. Analysis of the cytotoxic activity showed that wild celery oil and isofuranodiene are able to induce apoptosis in colon cancer cells in a time and concentration-dependent manner suggesting a potential role as models for the development of chemopreventive agents.

A forgotten vegetable (Smyrnium olusatrum L., Apiaceae) as a rich source of isofuranodiene

Smyrnium olusatrum, well known as wild celery or Alexanders, is a biennial herb belonging to the Apiaceae and used for many centuries as an edible vegetable because of the aromatic flavour of its parts. Its use on the table has decreased since the Middle Ages when it was replaced by common celery (Apium graveolens). In the present work the composition of the essential oils obtained by hydrodistillation of various plant parts was investigated by gas chromatography (GC-FID and GC-MS), while quantitation of a heat-sensitive compound, isofuranodiene, known for its anticancer activity, and of its Cope rearrangement product curzerene, was achieved by HPLC-DAD. All essential oils were composed mainly of furanosesquiterpenoids (54.1-76.2%) with isofuranodiene (19.5-45.8%) as the main constituent. Results showed that GC analysis provides underestimation (up to five times) of isofuranodiene levels in essential oils and that curzerene could be considered an artifact since it is produced during heating of plant material, occurring during hydrodistillation.

Cyclopeptide alkaloids from Ziziphus mucronata

Abstract In addition to the known alkaloid mucronine-D, two new cyclopeptide alkaloids were isolated from the roots of Ziziphus mucronata . The structures were elucidated by 1- and 2-DNMR techniques.