Chemistry and biological activity of azoprenylated secondary metabolites

Chemistry, biosynthesis and biological activity of terpenoids and meroterpenoids in bacteria and fungi isolated from different marine habitats

The marine environment with its vast biological diversity encompasses many organisms that produce bioactive natural products. Marine microorganisms are rich sources of compounds from many structural classes with a multitude of biological activities. The biosynthesis of microbial natural products depends on a variety of biotic and abiotic factors in the marine environment, including temperature, nutrients, salinity and interaction with other microorganisms. Terpenoids, as one of the most important groups of natural products in terrestrial microorganisms are important metabolites for marine microorganisms. Here, we have reviewed the chemistry, biosynthesis and pharmacological activities of terpenoids, extracted from marine microbes, and then survey their potential applications in drug development. We also discussed the different habitats in which marine microorganisms are found including sediments, the flora, such as seaweeds, sea grasses, and mangroves as well as the fauna like sponges and corals. Amongst these habitats, marine sediments are the major source for terpenoids producing microorganisms. The marine bacteria produce mostly meroterpenoids, while the fungi are well known for production of isoprenoids. Interestingly, marine-derived microbial terpenoids have some structural characteristics such as halogenation, which are catalyzed by specific enzymes with distinct substrate specificity. These compounds have anticancer, antibacterial, antifungal, antimalarial and anti-inflammatory properties. The information collected here might provide useful clues for developing new medications.

Synthesis and anti-inflammatory evaluation of N-sulfonyl anthranilic acids via Ir(III)-catalyzed C-H amidation of benzoic acids

The iridium(III)-catalyzed ortho-C-H amidation of benzoic acids with sulfonyl azides is described. These transformations allow the facile generation of N-sulfonyl anthranilic acids, which are known as crucial scaffolds found in biologically active molecules. In addition, all synthetic products were evaluated for in vitro anti-inflammatory activity against interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) with lipopolysaccharide (LPS)-induced RAW264.7 cells. Notably, compounds 4c and 4d, generated from p-OMe- and p-Br-sulfonyl azides, were found to display potent anti-inflammatory property stronger than that of well-known NSAIDs ibuprofen.

Can Small Chemical Modifications of Natural Pan-inhibitors Modulate the Biological Selectivity? The Case of Curcumin Prenylated Derivatives Acting as HDAC or mPGES-1 Inhibitors

Curcumin, or diferuloylmethane, a polyphenolic molecule isolated from the rhizome of Curcuma longa, is reported to modulate multiple molecular targets involved in cancer and inflammatory processes. On the basis of its pan-inhibitory characteristics, here we show that simple chemical modifications of the curcumin scaffold can regulate its biological selectivity. In particular, the curcumin scaffold was modified with three types of substituents at positions C-1, C-8, and/or C-8' [C5 (isopentenyl, 5-8), C10 (geranyl, 9-12), and C15 (farnesyl, 13, 14)] in order to make these molecules more selective than the parent compound toward two specific targets: histone deacetylase (HDAC) and microsomal prostaglandin E2 synthase-1 (mPGES-1). From combined in silico and in vitro analyses, three selective inhibitors by proper substitution at position 8 were revealed. Compound 13 has improved HDAC inhibitory activity and selectivity with respect to the parent compound, while 5 and 9 block the mPGES-1 enzyme. We hypothesize about the covalent interaction of curcumin, 5, and 9 with the mPGES-1 binding site.

Antibacterial Activities of Oxyprenylated Chalcones and Napthtoquinone against Helicobacter pylori

In this study, we synthesized and characterized the antibacterial activity of three naturally occurring oxyprenylated chalcones {xinjiachalcone A (1), (2 E)-1-{2,6-dihydroxy-4-[(3-methylbut-2-enyl)oxy]phenyl}-3-(4-hydroxyphenyl)prop-2-en-1-one (2), (2 E)-1-{2,6-dihydroxy-4-[(3-methylbut-2-enyl)oxy]phenyl}-3-phenylprop-2-en-1-one (3), and lawsone 2-isopentenyl ether (4)}. Using several strains of Helicobacter pylori, including clinical ones, minimum inhibitory concentration (MIC) values and bactericidal activities of these compounds were determined. Xinjiachalcone A (1), active principle of Glycyrrhiza inflata Batalin, was the most effective compound, showing both a low MIC and a strong bactericidal activity against H. pylori. This study suggests that these compounds represent potential natural molecules for the prevention and treatment of H. pylori associated diseases.

Phytochemistry and pharmacognosy of the genus Acronychia

The genus Acronychia (Rutaceae) comprise 44 species, most of which are represented by shrubs and small trees, distributed in a wide geographical area of South-Eastern Asia comprising China, India, Malaysia, Indonesia, Australia, and the islands of the western Pacific Ocean. Most of the species of the genus Acronychia have been used for centuries as natural remedies in the ethnomedical traditions of indigenous populations as anti-microbial, anti-fungal, anti-spasmodic, stomachic, anti-pyretic, and anti-haemorragic agent. Moreover fruits and aerial parts are used as food in salads and condiments, while the essential oil obtained from flowers and leaves has been employed in cosmetics production. Phytochemicals isolated from Acronychia spp. include acetophenones, quinoline and acridone alkaloids, flavonoids, cinnamic acids, lignans, coumarins, steroids, and triterpenes. The reported biological activities of the above mentioned natural compounds refer to anti-plasmodial, anti-cancer, anti-oxidant, anti-inflammatory, anti-fungal, and neuroprotective effects. The aim of this review is to examine in detail from a phytochemical and pharmacologically point of view what is reported in the current literature about the properties of phytopreparations or individual active principles obtained from plants belonging to the Acronychia genus.

In Vitro Anti-proliferative Effect of Naturally Occurring Oxyprenylated Chalcones

As a continuation of our ongoing studies aimed to depict the effects and mechanism of action of naturally occurring oxyprenylated phenylpropanoids and polyketides, in this paper we describe the synthesis and in vitro anti-proliferative effects of selected compounds belonging to the above cited classes of secondary metabolites on six cancer cell lines using the MTT colorimetric assay. Our study revealed that among the natural products tested, only oxyprenylated chalcones exhibited an appreciable effect (mean IC50 = 32 - 64 μM), while substituted alcohols, phenylpropenes, naphthoquinones, and aminoacid derivatives were by far less active or inactive.

Re-investigation of the Anthraquinone Pool of Rhamnus spp.: Madagascin from the Fruits of Rhamnus cathartica and R. intermedia

As a continuation of our ongoing studies aimed at revealing the presence of oxyprenylated anthraquinones in plants belonging to the genus Rhamnus, in this paper we describe the extraction and HPLC separation of madagascin (3-isopentenyloxyemodin) from the fruits of R. cathartica L. and R. intermedia Steud. & Hochst. The title compound is described herein for the first time as a component of fruit extracts of Rhamnus species.

Prenylated Polyhydroxy-p-terphenyls from Aspergillus taichungensis ZHN-7-07

Six new prenylated polyhydroxy-p-terphenyl metabolites, named prenylterphenyllins A-C (1-3) and prenylcandidusins A-C (5-7), and one new polyhydroxy-p-terphenyl with a simple tricyclic C-18 skeleton, named 4''-dehydro-3-hydroxyterphenyllin (4), were obtained together with eight known analogues (8-15) from Aspergillus taichungensis ZHN-7-07, a root soil fungus isolated from the mangrove plant Acrostichum aureum. Their structures were determined by spectroscopic methods, and their cytotoxicity was evaluated using HL-60, A-549, and P-388 cell lines. Compounds 1 and 8 exhibited moderate activities against all three cell lines (IC50 1.53-10.90 μM), whereas compounds 4 and 6 displayed moderate activities only against the P-388 cell line (IC50 of 2.70 and 1.57 μM, respectively).