Tomentosones A and B, hexacyclic phloroglucinol derivatives from the Thai shrub Rhodomyrtus tomentosa

Two phloroglucinols named tomentosones A and B (1 and 2) that each possess a novel hexacyclic ring system were isolated from the CH(2)Cl(2) extract of Rhodomyrtus tomentosa leaves. Their structures were elucidated from analyses of 2D NMR spectroscopic data. Tomentosone A inhibited the growth of chloroquine-resistant and -sensitive strains of the malaria parasite Plasmodium falciparum, with IC(50) values of 1.49 μM and 1.0 μM, respectively, while tomentosone B was significantly less active.     

Xanthones from the green branch of Garcinia dulcis

Two new prenylated xanthones, namely dulcisxanthone H and dulcisxanthone I along with garciniaxanthone C, were isolated from the dichloromethane extract of the green branch of Garcinia dulcis. Their structures were elucidated by the analysis of 1-D and 2-D NMR spectral data. Their antibacterial activities were also examined.     

Inhibitory Effects of Erythrosine/Curcumin Derivatives/Nano-Titanium Dioxide-Mediated Photodynamic Therapy on Candida albicans

This study focuses on the role of photosensitizers in photodynamic therapy. The photosensitizers were prepared in combinations of 110/220 µM erythrosine and/or 10/20 µM demethoxy/bisdemethoxy curcumin with/without 10% (w/w) nano-titanium dioxide. Irradiation was performed with a dental blue light in the 395–480 nm wavelength range, with a power density of 3200 mW/cm² and yield of 72 J/cm². The production of ROS and hydroxyl radical was investigated using an electron paramagnetic resonance spectrometer for each individual photosensitizer or in photosensitizer combinations. Subsequently, a PrestoBlue^® toxicity test of the gingival fibroblast cells was performed at 6 and 24 h on the eight highest ROS-generating photosensitizers containing curcumin derivatives and erythrosine 220 µM. Finally, the antifungal ability of 22 test photosensitizers, Candida albicans (ATCC 10231), were cultured in biofilm form at 37 °C for 48 h, then the colonies were counted in colony-forming units (CFU/mL) via the drop plate technique, and then the log reduction was calculated. The results showed that at 48 h the test photosensitizers could simultaneously produce both ROS types. All test photosensitizers demonstrated no toxicity on the fibroblast cells. In total, 18 test photosensitizers were able to inhibit Candida albicans similarly to nystatin. Conclusively, 20 µM bisdemethoxy curcumin + 220 µM erythrosine + 10% (w/w) nano-titanium dioxide exerted the highest inhibitory effect on Candida albicans.     

Inhibition of human lipoprotein oxidation by morelloflavone and camboginol from Garcinia dulcis

A biflavonoids, morelloflavone (1) and a prenyltated xanthone, camboginol (2), isolated from the fruits of Garcinia dulcis (Roxb.) Kurz., exhibited strong antioxidation effects in both Fe2+ -mediated and non-metal induced human low-density lipoprotein (LDL) oxidations. However, a well-known antioxidant, alpha-tocopherol (vitamin E), was found less potent than both compounds based on the same test systems.