New cytotoxic naphthopyrane derivatives from Adenaria floribunda

Dearomative gem-diprenylation of hydroxynaphthalenes by an engineered fungal prenyltransferase

Prenylation usually improves structural diversity and bioactivity in natural products. Unlike the discovered enzymatic gem-diprenylation of mono- and tri-cyclic aromatic systems, the enzymatic approach for gem-diprenylation of bi-cyclic hydroxynaphthalenes is new to science. Here we report an enzymatic example for dearomative C4 gem-diprenylation of α-hydroxynaphthalenes, by the F253G mutant of a fungal prenyltransferase CdpC3PT. Experimental evidence suggests a sequential electrophilic substitution mechanism. We also explained the alteration of catalytic properties on CdpC3PT after mutation on F253 by modeling. This study provides a valuable addition to the synthetic toolkit for compound prenylation and it also contributes to the mechanistic study of prenylating enzymes.

A new catalyst for regiospecific dearomative gem-diprenylation of α-hydroxynaphthalenes from the F253G mutant of the fungal prenyltransferase CdpC3PT.

Spontaneous oxidative cyclisations of 1,3-dihydroxy-4-dimethylallylnaphthalene to tricyclic derivatives

The attachment of a dimethylallyl moiety to C4 of 1,3-dihydroxynaphthalene led to spontaneous oxidative cyclisations, resulting in the formation of two tetrahydrobenzofuran and one bicyclo[3.3.1]nonane derivatives. Incubation under an 18O-rich atmosphere proved that both the incorporated oxygen atoms originated from O2. A radical-involved mechanism is proposed for these cyclisations.

UHPLC-UV/Vis Quantitative Analysis of Hydroxylated and O-prenylated Coumarins in Pomegranate Seed Extracts

A simple and rapid analytical UHPLC methodology with spectrophotometric (UV/Vis) detection, coupled with different extraction procedures, has been perfected to investigate the presence of biologically active O-prenylated umbelliferone derivatives, such as auraptene and umbelliprenin, in pomegranate (Punica granatum L.) seed extracts. Absolute ethanol was the most efficient extraction solvent in terms of yields, after a short ultrasound-assisted. The highest concentration values recorded under these experimental conditions were 1.99 μg/g of dry extract and 6.53 μg/g for auraptene and umbelliprenin, respectively. The parent metabolite umbelliferone was also detected (0.67 μg/g). The extraction and UHPLC analytical methodology set up in the present study proved to be an efficient, powerful, and versatile technique for the simultaneous qualitative analysis and quantification of oxyprenylated coumarins in pomegranate seed extracts. The characterization of such secondary metabolites in the mentioned phytopreparation represents, to the best of our knowledge, the first example in the literature.

2α-Acetoxy-15-acetylartemisiifolin, a new Anti-trypanosomal Sesquiterpene Lactone from Mikania guaco

Mikania guaco Bonpl. methanol extract showed an interesting activity against Trypanosoma cruzi with an IC50 of 4 μg/mL. Bioassay-guided fractionation of the methanol extract resulted in the isolation of a new sesquiterpene lactone, 2α-acetoxy, 15-acetylartemisiifolin (1), which was shown to be active (IC50 = 25 μM) against the amastigote form of T. cruzi,. The chemical structure of 1 was elucidated using 2-D NMR techniques and mass spectrometry.

A promiscuous prenyltransferase from Aspergillus oryzae catalyses C-prenylations of hydroxynaphthalenes in the presence of different prenyl donors

Prenyltransferases of the dimethylallyltryptophan synthase (DMATS) superfamily are involved in the biosynthesis of secondary metabolites and show broad substrate specificity towards their aromatic substrates with a high regioselectivity for the prenylation reactions. Most members of this superfamily accepted as prenyl donor exclusively dimethylallyl diphosphate (DMAPP). One enzyme, AnaPT from Neosartorya fischeri, was reported recently to use both DMAPP and geranyl diphosphate (GPP) as prenyl donors. In this study, we demonstrate the acceptance of DMAPP, GPP and farnesyl diphosphate (FPP) by a new member of this superfamily, BAE61387 from Aspergillus oryzae DSM1147, for C-prenylations of hydroxynaphthalenes.

Antifungal metabolites from the roots of Diospyros virginiana by overpressure layer chromatography

A preparative overpressure layer chromatography (OPLC) method was successfully used for the separation of two new natural compounds, 4-hydroxy-5,6-dimethoxynaphthalene-2-carbaldehyde (1) and 12,13-didehydro-20,29-dihydrobetulin (2) together with nine known compounds, including 7-methyljuglone (3), diospyrin (4), isodiospyrin (5), shinanolone (6), lupeol (7), betulin (8), betulinic acid (9), betulinaldehyde (10), and ursolic acid (11) from the acetone extract of the roots of Diospyros virginiana. Their identification was accomplished by 1D- and 2D-NMR spectroscopy and HR-ESI-MS methods. All the isolated compounds were evaluated for their antifungal activities against Colletotrichum fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, Phomopsis obscurans, and P. viticola using in vitro micro-dilution broth assay. The results indicated that compounds 3 and 5 showed high antifungal activity against P. obscurans at 30 μM with 97.0 and 81.4% growth inhibition, and moderate activity against P. viticola (54.3 and 36.6%). It appears that an optimized OPLC system offers a rapid and efficient method of exploiting bioactive natural products.