Hydroxylation of the diterpenes ent-kaur-16-en-19-oic and ent-beyer-15-en-19-oic acids by the fungus Aspergillus niger.

The diterpenes ent-kaur-16-en-19-oic acid (1) and ent-beyer-15-en-19-oic acid (2) are the major constituents of a spasmolytic diterpenic mixture obtained from the roots of Viguiera hypargyrea, a Mexican medicinal plant. Microbial transformation of 1 and 2 was performed with Aspergillus niger. Two metabolites, ent-7alpha,11beta-dihydroxy-kaur-16-en-19-oic acid (4) and ent-1beta,7alpha-dihydroxy-kaur-16-en-19-oic acid (5), were isolated from the incubation of 1, and one metabolite, ent-1beta,7alpha-dihydroxy-beyer-15-en-19-oic acid (6), was isolated in high yield (40%) from 2. The structures were elucidated on the basis of spectroscopic analyses and confirmed by X-ray crystallographic studies. Compounds 1-4 and 6 and methyl ester derivatives 4a and 6a were evaluated for their ability to inhibit the electrically induced contraction of guinea-pig ileum. Compounds 1, 3, 4, 4a and 5 were significantly active. These results showed that dihydroxylation of 1 at 7beta, 11alpha-, and 1alpha, 7beta-positions resulted in a loss of potency.

Hypoglycemic effect and chlorogenic acid content in two Cecropia species.

The hypoglycemic effect of methanol leaf extracts from Cecropia obtusifolia and C. peltata was evaluated in healthy mice. A significant decrease (p < 0.05) in plasma glucose levels was recorded 2 and 4 h after a single oral administration of methanol extracts (1 g/kg). This effect was correlated with the chlorogenic acid contents in both species; C. peltata, containing 19.84 +/- 1.64 mg of chlorogenic acid/g of dried leaves produced the highest decrease (D(alpha 2,60) = 20.18, p < 0.05) of plasma glucose levels (52.8%). The extracts of C. obtusifolia from Tabasco and Veracruz, showed similar hypoglycemic effects (33.3% and 35.7%, respectively) and chlorogenic acid contents (Tukey(0.05) = 1.8859) (13.3 +/- 3.2 mg/g and 13.1 +/- 1.6 mg/g, respectively). The hypoglycemic effect produced by different doses (0.1, 0.25, 0.50, 0.75 and 1 g/kg body wt, p.o.) of C. peltata showed a lineal relationship with chlorogenic acid content, reaching an ED(50) = 0.540 g/kg body wt for extract, and an ED(50) = 10.8 mg/kg body wt for chlorogenic acid. These results suggest that C. peltata is a better hypoglycemic agent than C. obtusifolia, and it could be considered for developing a phytomedicinal product to carry out clinical trials.

Antimycotic spirostanol saponins from Solanum hispidum leaves and their structure-activity relationships.

A new spirostanol saponin, together with three known saponins, were isolated from the leaves of Solanum hispidum. The structure of the new saponin was elucidated as 6alpha-O-beta-D-quinovopyranosyl-(25S)-5alpha-spirostan-3beta-ol (1) on the basis of spectroscopic analysis (1H NMR, 13C NMR, 1H-1H COSY, HMQC, HMBC, and HRFABMS). All of the isolated compounds showed antimycotic activity. The most active compound was 6alpha-O-[beta-D-xylopyranosyl-(1-->3)-beta-D-quinovopyranosyl]-(25S)-5alpha-spirostan-3beta-ol (2) (MIC = 25 microg/mL against both Trichophyton mentagrophytes and T. rubrum). The structure-activity relationships of the isolated compounds and those isolated from S. chrysotrichum are discussed.