Antimycobacterial neolignans isolated from Aristolochia taliscana

Tuberculosis (TB - Mycobacterium tuberculosis) is an ancient infectious disease that has appeared once again as a serious worldwide health problem and now comprises the second leading cause of death resulting from a single infection. The prevalence of multidrug resistance (MDR) TB is increasing and therapeutic options for treatment are not always accessible; in fact, some patients do not respond to the available drugs. Therefore, there is an urgent need to develop novel anti-TB agents. The aim of the present study was to screen extracts of Aristolochia taliscana, a plant used in traditional Mexican medicine to treat cough and snake bites, for antimycobacterial activity. The hexanic extract of A. taliscana was tested by microdilution alamar blue assay against Mycobacterium strains and bioguided fractionation led to the isolation of the neolignans licarin A, licarin B and eupomatenoid-7, all of which had antimycobacterial activity. Licarin A was the most active compound, with minimum inhibitory concentrations of 3.12-12.5 ìg/mL against the following M. tuberculosis strains: H37Rv, four mono-resistant H37Rv variants and 12 clinical MDR isolates, as well as against five non-tuberculous mycobacteria (NTM) strains. In conclusion, licarin A represents a potentially active anti-TB agent to treat MDR M. tuberculosis and NTM strains.

Quercetin glycosides in Psidium guajava L: leaves and determination of a spasmolytic principle

The traditional herbal remedy from Psidium guajava leaves had been medically proposed in mexico as effective treatment of acute diarrhea. A methanolic leaf extract was subjected to a bioassay-guided isolation of spasmolytic constituents. Six fractions were separated on a polyvinylpolypyrrolidine (PVPP) columm using a water methanol-gradient. The fraction containing flavonols inhibited peristalsis of guinea pig ileum in vitro. A trace of quercetin aglycone together with five glycosides was isolated from this active fraction and identified as quercentin 3-O-alpha-L-arabinoside (guajaravin); quercetin 3-O-ß-D-glucoside (isoquercetin); quercetin 3-O-ß-D-galactoside (hyperin); quercetin 3-O-ß-L-rhamnoside (quercitrin) and quercetin 3-O-gentobioside. Biological activity of each pure compound was studied in the same bioassay. Obtained results suggets that the spasmolytic activity of the Psidium guajava leaf remedy is mainly due to the aglycone quercetin, present in the leaf and in the extract mainly in the form of live flavonols, and whose effect is produced when these products are hydrolyzed by gastrointestinal fluid

Calcium-antagonist effect of quercetin and its relation with the spasmolytic properties of Psidium guajava L

The antidiarrheal properties of water ad methanolic extracts of Psidium guajava leaves have been demonstrated with anteriority and their spasmolytic effect was attributed to quercetin, a flavonoid conatined in this plant. The present paper reports the intestinal smooth muscle relaxation produced by quercetin on isolated guinea pig ileum previously contracted by a depolarizing KCl solution. Quercetin also inhibited intestinal contraction induced by different concentrations of calcium, shifting the contraction curve to the right showing a clear clacium-antagonistic efecct. Quercetin effect on ileal and aortic smooth muscles ar compared, the ileum being more sensitive to this flavonoid. The clacium antagonist property of quercetin is discussed and also its contribution to explain the spasmolytic effect of this popular herbal remedy