John A. Rideout

Two New UV-Absorbing Compounds from Stylophora pistillata: Sulfate Esters of Mycosporine-like Amino Acids

Abstract Two new water soluble 320 nm UV-absorbing compounds, sulfate esters of two imino mycosporines, were isolated from methanol extracts of a reef-building coral and purified by HPLC. Structural elucidation yielded the molecular formulae C 12 H 19 N 2 O 9 S ( 5 ) and C 11 H 17 N 2 O 9 S ( 6 ). These have been given the trivial names Palythine-Thr-sulfate and Palythine-Ser-sulfate respectively.

Antifungal metabolites from Blumea balsamifera

The leaves of Blumea balsamifera afforded icthyothereol acetate, cryptomeridiol, lutein, and β-carotene. The structures of icthyothereol acetate (1) and cryptomeridiol (2) were elucidated by extensive 1D and 2D NMR spectroscopy, while those of lutein and β-carotene were identified by comparison with literature data. Antimicrobial tests indicated that 1 has moderate activity against the fungi Aspergillus niger, Trichophyton mentagrophytes, and Candida albicans, while 2 has low activity against A. niger, T. mentagrophytes, and C. albicans. Both compounds have no antimicrobial activity against Psuedomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, and Escherichia coli.

Application of the shrinking core model to the kinetics of extraction of gold(I), silver(I) and nickel(II) cyanide complexes by novel anion exchange resins

This paper describes an investigation of the kinetics of loading of gold(I), silver(I), and nickel(II) cyanide complexes onto two novel anion exchange resins with high selectivity for the linear dicyanoaurate(I) and dicyanoargentate(I) complexes. The kinetic data fit well to a shrinking core theoretical model, and indicate that in all three complexes, the loading is controlled by the rate of diffusion of the ions penetrating the reacted layer. Diffusion coefficients were determined and those of Au(I) and Ag(I) cyano complexes are similar to one another but much higher (30 to 60 times) those of the Ni(II) cyano complex on these two resins.

Tetranortriterpenoids from Azadirachta indica

Abstract Azadirachta indica afforded two novel tetranortriterpenoids by gravity column chromatography. Their structures were elucidated by extensive 1D and 2D NMR techniques.

New Cycloartenol Esters from Ixora Coccinea

The air-dried flowers of Ixora coccinea L. afforded two new cycloartenol esters (1a and 1b), lupeol fatty ester, lupeol, ursolic acid, oleanolic acid, and sitosterol. The structures of 1a and 1b were elucidated by extensive 1D and 2D NMR spectroscopy and MS.

Bioactive triterpenes from Diospyros blancoi.

The ethyl acetate extract of the air-dried leaves of Diospyros blancoi afforded isoarborinol methyl ether (1), a mixture of α-amyrin palmitate, α-amyrin palmitoleate, β-amyrin palmitate and β-amyrin palmitoleate (2) in a 13 : 4 : 3 : 1 ratio, and squalene. The structures of 1, 2 and squalene were elucidated by extensive 1D and 2D NMR spectroscopy. Compounds 1 and 2 exhibited antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Candida albicans, Staphylococcus aureus and Trichophyton mentagrophytes, and were found inactive against Bacillus subtilis and Aspergillus niger. Sample 2 exhibited significant analgaesic and anti-inflammatory activities.

Isolation and structure of a novel mycosporine-like amino acid from the reef-building corals Pocillopora damicornis and Stylophora pistillata

Abstract A novel 330 nm UV absorbing compound, a methylamine substituted mycosporine ( 1 ), was isolated from methanol extracts of two hermatypic scleractinians. Structural elucidation yielded the molecular formula C 13 H 22 N 2 O 6 . This was given the trivial name Mycosporine-methylamine:threonine.

Nonsymmetrical beta-carboline dimers from an Ascidian, Didemnum sp.

In addition to the previously reported symmetrical beta-carboline dimer 1, an ascidian Didemnum sp. yielded trace amounts of beta-carboline and the nonsymmetrical beta-carboline dimers 2, 3, and 5. The structures of the nonsymmetrical dimers were confirmed by nonselective synthesis of 2 and 3 from beta-carboline, which also yielded additional dimers 4 and 6.

Terpenoids and sterols from Lagerstroemia speciosa

The leaves of Lagerstroemia speciosa afforded a new natural product, 31-norlargerenol acetate (4), along with known compounds 24-methylenecycloartanol acetate (1), its 31-nor analog (2), largerenol acetate (3), tinotufolins C (5) and D (6), lutein, phytol, sitosterol and sitosterol acetate. The structure of 4 was elucidated by 1D and 2D NMR and mass spectroscopy.

Ionone derivatives from Alternanthera sessilis

The chloroform extract of the air-dried leaves of Alternanthera sessilis afforded a mixture of diastereomers of a new ionone derivative 1 whose structures were elucidated by extensive 1D and 2D NMR spectroscopy and mass spectrometry. Oxidative cleavage of 1 to aldehyde 3 with manganese dioxide confirmed diastereoisomerism arose from a racemic side chain chiral centre. Antimicrobial tests on the mixture of diastereomers and the derivative indicated that they have low activities against Pseudomonas aeruginosa and Trichophyton mentagrophytes.