Cytotoxic podophyllotoxin type-lignans from the steam bark of Bursera fagaroides var. fagaroides.

The hydroalcoholic extract of the steam bark of B. fagaroides var. fagaroides displayed potent cytotoxic activity against four cancer cell lines, namely KB (ED50 = 9.6 × 10(-2) µg/mL), PC-3 (ED50 = 2.5 × 10(-1) µg/mL), MCF-7 (ED50 = 6.6 µg/mL), and HF-6 (ED50 = 7.1 × 10(-3) µg/mL). This extract also showed anti-tumour activity when assayed on mice inoculated with L5178Y lymphoma cells. Bioactivity-directed isolation of this extract, afforded seven podophyllotoxin-type lignans identified as podophyllotoxin (1), ß-peltatin-A-methylether (2), 5'-desmethoxy-ß-peltatin-A-methylether (3), desmethoxy-yatein (4), desoxypodophyllotoxin (5), burseranin (6), and acetyl podophyllotoxin (7) by 1D and 2DNMR and FAB-MS analyses, and comparison with reported values. All the isolated compounds showed potent cytotoxic activity in the cell lines tested, especially compound 3, which exhibited greater activity than camptothecin and podophyllotoxin against PC-3 (ED50= 1.0 × 10(-5) µg/mL), and KB (ED50 = 1.0 × 10(-5) µg/mL). This is the first report of the isolation of podophyllotoxin and its acetate in a Bursera species.

Effect of Gnaphalium conoideum HBK on guinea pig airway smooth muscle: role of L-type Ca2+ channels.

Plants from the Gnaphalium genus have been used in the Mexican traditional medicine for digestive and respiratory complaints. In the present study, the effect of methanolic extract from Gnaphalium conoideum HBK on the responses to contractile agonists was assessed in guinea pig tracheas, and the possible role of L-type Ca2+ channels was explored in tracheal guinea pig isolated myocytes. Cumulative concentration-response curves to carbachol or histamine, as well as contractile responses to 60 mM KCl were evaluated with or without 30 min preincubation with 20 or 100 microg ml(-1) Gnaphalium conoideum. Likewise, intracellular Ca2+ concentrations were measured by microfluorometric method (fura-2 AM) in isolated tracheal myocytes with or without preincubation with 0.1, 0.31 or 1 microg ml(-1)Gnaphalium conoideum. We found that methanolic extract from Gnaphalium conoideum significantly diminished the contractile responses to histamine, but not to carbachol or KCl. In isolated myocytes, Gnaphalium conoideum significantly reduced the intracellular Ca2+ rise induced by 60 mM KCl. Because histamine contractile responses are largely dependent on extracellular Ca2+, and KCl responses are mainly mediated through L-type Ca2+ channels, our results suggested that methanolic extract from Gnaphalium conoideum might be acting as a partial blocker of these Ca2+ channels.