Neurite Outgrowth-Inducing Drimane-Type Sesquiterpenoids Isolated from Cultures of the Polypore Abundisporus violaceus MUCL 56355.

Abundisporin A (1), together with seven previously undescribed drimane sesquiterpenes named abundisporins B-H (2-8), were isolated from a polypore, Abundisporus violaceus MUCL 56355 (Polyporaceae), collected in Kenya. Chemical structures of the isolated compounds were elucidated based on exhaustive 1D and 2D NMR spectroscopic measurements and supported by HRESIMS data. The absolute configurations of the isolated compounds were determined by using Mosher's method for 1-4 and TDDFT-ECD calculations for 4 and 5-8. None of the isolated compounds exhibited significant activities in either antimicrobial or cytotoxicity assays. Notably, all of the tested compounds demonstrated neurotrophic effects, with 1 and 6 significantly increasing outgrowth of neurites when treated with 5 ng/mL NGF.

Antidermatophytic quinolizidine alkaloids from Calpurnia aurea subsp. aurea (Aiton) Benth.

From the leaves and stem bark of the Kenyan medicinal plant Calpurnia aurea subsp. aurea, four previously undescribed quinolizidine alkaloids namely, 2ß-methoxy-13α-O-(2'-pyrrolylcarbonyl) virgiline, 2α-methoxy-13ß-O-(2'-pyrrolylcarbonyl) virgiline, 3α-O-angelate-2ß-hydroxy-13α-O-(2'-pyrrolylcarbonyl) virgiline, 2,3-dehydro-virgiline were isolated together with four known ones. Structural elucidation of the compounds was based on 1D and 2D NMR spectroscopy and mass spectrometry. Their relative configurations were determined by NOESY correlations and literature. The quinolizidine alkaloids were tested against Trichophyton rubrum, Trichophyton interdigitale, Trichophyton benhamiae, Microsporum canis and Nannizzia gypsea, common causative agents of most of the tinea infections in human. All the isolated quinolizidine alkaloids exhibited antidermatophytic activity with MIC ranging from 37.5 µg/ml to 300 µg/ml.

Microporenic Acids A-G, Biofilm Inhibitors, and Antimicrobial Agents from the Basidiomycete Microporus Species.

The need for effective compounds to combat antimicrobial resistance and biofilms which play important roles in human infections continues to pose a major health challenge. Seven previously undescribed acyclic diterpenes linked to isocitric acid by an ether linkage, microporenic acids A-G (1-7), were isolated from the cultures of a hitherto undescribed species of the genus Microporus (Polyporales, Basidiomycota) originating from Kenya's Kakamega forest. Microporenic acids D and E (4 and 5) showed antimicrobial activity against a panel of Gram positive bacteria and a yeast, Candida tenuis. Moreover, microporenic acids A and B (1 and 2) demonstrated dose-dependent inhibition of biofilm formation by Staphylococcus aureus. Compound 1 further showed significant activity against Candida albicans and Staphylococcus aureus preformed biofilms.