Abstract
Pseudopalawania siamensisgen. et sp. nov., from northern Thailand, is introduced based on multi-gene analyses and morphological comparison. An isolate was fermented in yeast malt culture broth and explored for its secondary metabolite production. Chromatographic purification of the crude ethyl acetate (broth) extract yielded four tetrahydroxanthones comprised of a new heterodimeric bistetrahydroxanthone, pseudopalawanone (1), two known dimeric derivatives, 4,4′-secalonic acid D (2) and penicillixanthone A (3), the corresponding monomeric tetrahydroxanthone paecilin B (4), and the known benzophenone, cephalanone F (5). Compounds 1–3 showed potent inhibitory activity against Gram-positive bacteria. Compounds 2 and 3 were inhibitory against Bacillus subtilis with minimum inhibitory concentrations (MIC) of 1.0 and 4.2 μg/mL, respectively. Only compound 2 showed activity against Mycobacterium smegmatis. In addition, the dimeric compounds 1–3 also showed moderate cytotoxic effects on HeLa and mouse fibroblast cell lines, which makes them less attractive as candidates for development of selectively acting antibiotics.
Highlights
Fungi are potentially known as a promising source of bioactive compounds for drug discovery [1]
The combined dataset of large subunit nuclear rDNA (LSU), small subunit nuclear rDNA (SSU), RPB2, internal transcribed spacer (ITS) and TEF sequence data including our new strains were analyzed by maximum likelihood (ML) and Bayesian analyses
The combined sequence alignment is comprised of 155 taxa (6131 characters with gaps), which include representative strains from Lecanoromycetes as outgroup taxa
Summary
Fungi are potentially known as a promising source of bioactive compounds for drug discovery [1]. A few contemporary studies in Thailand have been focusing on saprobic fungi in Dothideomycetes as a source for finding novel bioactive compounds. A novel Thai Dothideomycete, Pseudobambusicola thailandica, has yielded six new compounds with nematicidal and antimicrobial activity [8]. Some phenalenones from another new Thai Pseudolophiostoma species were found to selectively inhibit α-glucosidase and lipase [11]. In spite of these recent discoveries, the study of bioactive compounds from Thai and other tropical Dothideomycetes is still in the initial stages of research
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