Myrna Tepora’s research while affiliated with De La Salle University and other places

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.

The air-dried leaves of Tectona philippinensis, an endemic and endangered Philippine medicinal tree, afforded four new chromomoric acid derivatives ( 1, 2, 3a, and 3b). Their structures were elucidated by extensive 1D and 2D NMR spectroscopy. Antimicrobial testing was carried out on 1- 3 against a panel of bacteria and fungi.

The air-dried flowers of Tithonia diversifolia, commonly known as native sunflower, afforded tagitinin C (1), fatty acid esters of faradiol (2), squalene (3), and a mixture (1:2) of stigmasterol (4) and sitosterol (5). The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy, while the structures of 2 to 5 were elucidated by a comparison of their 1H and 13C NMR spectral data with those found in the literature. Antimicrobial tests on 1 indicated theat it was moderately active against S. aureus and C. albicans; slightly active against E. coli, P. aeruginosa and T. mentagrophytes; and inactive against B. subtilis 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.

Two chromenes isolated from Eupatorium toppingianum were identified as 6-hydroxy-7,8-dimethoxy-2,2-dimethylchromene and 6-(1-hydroxyethyl)-7,8-dimethoxy-2,2-dimethylchromene. Their structures were elucidated by 1D and 2D NMR techniques. Antimicrobial tests on 6-(1-hydroxyethyl)-7,8-dimethoxy-2,2-dimethylchromene indicated that is is active against Staphylococcus aureus, while 6-hydroxy-7,8-dimethoxy-2,2-dimethylchromene is active against Trichophyton mentagrophytes.