John Rideout’s research while affiliated with Central Queensland University and other places

The ethyl acetate extract of the stem bark of Pouteria campechiana afforded 3b, 28- dihydroxy-olean-12-enyl fatty acid ester 1, a mixture of a fatty acid ester of oleanolic acid 2a and a fatty acid ester of betulinic acid 2b in a 0.3:1 ratio, and spinasterol 3 by silica gel chromatography. The structures of 1-2b were elucidated by extensive 1D and 2D NMR spectroscopy. The structure of 3 was identified by comparison of its 1H NMR data with spinasterol. Antimicrobial tests on 1 and a mixture of 2a and 2b indicated that they are slightly active against the bacteria, Escherichia coli and Pseudomonas areruginosa and the fungi, Candida albicans and Trichophyton mentagrophytes. They are inactive against Staphylococcus aureus, Bacillus subtilis, and Aspergillus niger.

The dichloromethane extract of the air-dried leaves of Shorea guiso, a critically endangered Philippine tree, afforded shoreic acid (1) by column chromatography. The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy. Compound 1 exhibited antibacterial activity against E. coli, P. aeruginosa, S. aureus, and B. subtilis with activity indices (AI) of 0.2, 0.3, 0.5 and 0.4, respectively. It also showed antifungal activity against C. albicans and T. mentagrophytes with AI of 0.2 and 0.3, respectively. It was inactive against A. niger.

The dichloromethane extract of the air-dried leaves of Pycnarrhena manillensis afforded stigmast-4-en-3,6-dione (1) and stigmast-4-en-3-one (2) by silica gel chromatography. Their structures were elucidated by extensive 1D and 2D NMR spectroscopy. 1 and 2 exhibited moderate antifungal activity against C. albicans and low antibacterial activity against E. coli and P. aeruginosa. 2 was slightly active against S. aureus, while 1 was inactive against this bacterium. Both compounds were inactive against B. subtilis, T. mentagrophytes and A. niger.

Taraxacum officinale, commonly known as dandelion is reported to exhibit antimicrobial properties. This study was conducted to isolate the dichloromethane soluble constituents of the plant which may contribute to this property. The dichloromethane extract of the leaves of Taraxacum officinale afforded taraxasteryl acetate (1a), lupeol acetate (1b), taraxinic acid (2a), 11,13-dihydrotaraxinic acid (2b), phytyl fatty acid ester (3), and squalene (4). The structures of 2a and 2b were elucidated by extensive 1D and 2D NMR spectroscopy, while 1a, 1b, 3 and 4 were identified by comparison of their 1H and 13C NMR data with those found in the literature. The mixture of 1a and 1b indicated low activites against the bacteria: E. coli, S. aureus, P. aeruginosa and fungi: C. albicans and T. mentagrophytes. It was inactive against B. subtilis and A. niger.

The dichloromethan extract of the leaves of Andrographis paniculata afforded 14-deoxy-12-hydroxyandrographolide 1, a mixture of 14-deoxy-11,12-dihydroandrographolide 2b, B-carotene, phytyl fatty acid esters, squalene and a mixture of sitosterol and stigmasterol. The structure of 14-deoxy-12-hydroxyandrographolide was elucidated by extensive 1D and 2D NMR spectroscopy. Antimicrobial tests on 1 indicated that it has moderate activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Trichophyton mentagrophytes. This diterpene was also found to be cytotoxic to human lung carcinoma (A549) with an IC50 of 20.85 microgram/mL and less cytotoxic towards the normal Chinese hamster ovarian cell with an IC50 of 38.92 microgram/mL.

The dichloromethane extract of the aerial parts of Emilia sonchifolia afforded a mixture of taraxasteryl acetate (1a) and lupeol acetate (1b) in a 1:0.3 ratio. Their structures were elucidated by extensive 1D and 2D NMR spectroscopy.

The dichloromethane extract of the corm of Musa errans, an endemic form of wild banana afforded 31-norcyclolaudenone (1), squalene, and a mixture of stimasterol and sitosterol. The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy. Antimicrobial tests on 1 indicated that it has low activity against C. albicans, E. coli, P. aeruginosa, and T. mentagrophytes; and inactive against B. subtilis, S. aureus and A. niger.

The air-dried fruit peel of Lansium domesticum Correa afforded five onoceroid triterpenes: 3β- hydroxyonocera-8(26),14-dien-21-one (1), α,γ-onoceradienedione (2), lansiolic acid (3), lansionic acid (4) and lansioside C (5), while the air-dried seeds afforded 3 and germacrene D (6). Antimicrobial tests on 1-6 gave the following results. 2 has high activity against P. aeruginosa, while 1, 3, 4 and 5 have moderate activities against this microorganism. 5 and 4 have moderate and low activities against B. subtilis, respectively, while 3 and 5 have low activities against S. aureus. All the compounds tested have moderate activities against C. albicans and A. niger, and low activities against T. mentagrophytes.

Air-dried leaves of Citrus microcarpa Bunge afforded 3',4',5,6,7,8-hexamethoxyflavone (1) and squalene. The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy. Antimicrobial tests on 1 indicated that it has moderate activity against the fungus, C. albicans and low activity against the bacteria, P. aeruginosa and B. subtilis and fungi, T. mentagrophytes and A. niger.

The dichloromethane extract of the air-dried flowers of Michelia champaca afforded 11,13-dehydrolanuginolide (1) by silica gel chromatography. The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy. Antimicrobial tests on 1 indicated that it is moderately active against the fungus, Candida albicans. It has low activity against the bacteria, P. aeruginosa and e. coli and the fungus, T. mentagrophytes. It is inactive against S. aureus, B. subtilis and A. niger.