Enzymatic reduction of 9-methoxytariacuripyrone by Saccharomyces cerevisiae and its antimycobacterial activity.

Biotransformation processes have been successfully utilized to obtain products of pharmaceutical, chemical, food, and agricultural interest, which are difficult to obtain by classic chemical methods. The compound with antituberculous activity, 9-methoxy-tariacuripyrone (1), isolated from Aristolochia brevipes, was submitted to biotransformation with the yeast Saccharomyces cerevisiae under culture, yielding 5-amino-9-methoxy-3,4-dihydro-2H-benzo[h]chromen-2-one (2). The structure of (2) was elucidated on the basis of spectroscopic analyses. The results mainly show the reduction of the double bond and the nitro group of compound (1). Metabolite (2) demonstrated an increase in anti-tuberculous activity (MIC = 3.12 µg/mL) against the drug-sensitive Mycobacterium tuberculosis (H37Rv) strain, with respect to that shown by (1).

Antibacterial activity of Aristolochia brevipes against multidrug-resistant Mycobacterium tuberculosis.

The increased incidence of Multidrug-Resistant Mycobacterium tuberculosis (MDR-MT) requires the search for alternative antimycobacterial drugs. The main aim of this study was to evaluate the dichloromethane extract from Aristolochia brevipes (Rhizoma) and the compounds isolated from this extract against several mycobacterial strains, sensitive, resistant (monoresistant), and clinical isolates (multidrug-resistant), using the alamarBlue™ microassay. The extract was fractionated by column chromatography, yielding the following eight major compounds: (1) 6α-7-dehydro-N-formylnornantenine; (2) E/Z-N-formylnornantenine; (3) 7,9-dimethoxytariacuripyrone; (4) 9-methoxy-tariacuripyrone; (5) aristololactam I; (6) ß-sitosterol; (7) stigmasterol; and (8) 3-hydroxy-α-terpineol. The structures of these compounds were elucidated by 1H- and 13C- (1D and 2D) Nuclear Magnetic Resonance (NMR) spectroscopy. This study demonstrates that the dichloromethane extract (rhizome) of A. brevipes possesses strong in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (Minimum Inhibitory Concentration value [MIC], 12.5 µg/mL). The most active compound against all mycobacterial strains tested was the compound aristolactam I (5), with MIC values ranging between 12.5 and 25 µg/mL. To our knowledge, this the first report of antimycobacterial activity in this plant.

Mycological and electron microscopic study of Solanum chrysotrichum saponin SC-2 antifungal activity on Candida species of medical significance.

Solanum chrysotrichum is utilized in traditional Mexican medicine for the treatment of mycotic skin infections. Several microbiological studies have provided evidence of its antifungal activity against dermatophytes and yeasts. S. chrysotrichum saponins have been identified as a group of compounds with antifungal activity and saponin SC-2 has demonstrated to be the most active. Previous clinical studies have shown the therapeutic effectiveness of S. chrysotrichum-derived saponin-standardized herbal products in the treatment of Tinea pedis and Pityriasis capitis. There is no previous evidence of the activity of these saponins against Candida non-albicans species, or fluconazole- and ketoconazole-resistant Candida strains. The present study reports the biological activity of the SC-2 saponin (inhibitory concentration [IC (50)] and minimum fungicide concentration [MFC]), against 12 Candida strains of clinical significance ( C. albicans, five strains; C. glabrata and C. parapsilosis, two; C. krusei, C. lusitaniae and C. tropicalis, one), including some fluconazole (Fluco)- and ketoconazole (Keto)-resistant clinical isolates. In addition, SC-2-associated microstructural alterations were reported in four of the above-mentioned Candida species. Seven strains had IC (50) of 200 microg/mL for SC-2, 400 microg/mL was found in four strains, and 800 microg/mL for a sole C. glabrata strain. Susceptibility to SC-2 saponin was as follows: C. albicans = C. lusitaniae > C. krusei > C. glabrata. The MFC was 800 microg/mL for the majority of strains (nine), 400 microg/mL for C. albicans (two strains) and C. lusitaniae. The ultrastructural Candida changes originated by SC-2 included the following: 1) damage on cytoplasmic membrane and organelles; 2) changes in cell wall morphology and density, with separation of cytoplasmatic membrane from cell wall and disintegration of the latter; and 3) total degradation of cellular components and death. Changes were manifested from 6 h of incubation, reaching their maximum effect at 48 h. In conclusion, the saponin SC-2 possesses fungicide and fungistatic activity on different Candida albicans and non- albicans species (including some azole-resistant strains) with IC (50) values of 200 microg/mL (in Fluco-susceptible strains) and of 400 - 800 mug/mL (in Fluco-resistant strains). Additionally, we observed by transmission electron microscopy (TEM) that saponin SC-2 causes severe changes in all fungal cell membranes, and to a lesser degree on the cell wall.