α-Glucosidase Inhibitory and Cytotoxic Taxane Diterpenoids from the Stem Bark of Taxus wallichiana

From a CH2Cl2 extract of the bark of Taxus wallichiana, six new taxoids, wallitaxanes A F (1-6), were isolated, together with 29 known compounds. The structures of the new compounds Were elucidated on the basis of spectroscopic data interpretation. Wallitaxane D (4) was identified as an opened oxetane-type taxoid having the first naturally occurring C(H)-20 acetal group, while wallitaxanes E (5) and F (6) are representative of the rare abeo-taxoid class. The isolated compounds were evaluated for their alpha-glucosidase inhibitory activity and for cytotoxicity against the HeLa-human cervical cancer cell line. In the present work, takanes were found to exhibit alpha-glucosidase inhibitory activity for the first time, and Wallitaxane (1) showed the most potent effect, with an IC50 value of 3.6 mu M. In turn, 7-epi-taxol (16) and 7-epi-10-deacetyltaxol (17) showed IC50 values of 0.05 and 0.085 nM, respectively, against HeLa cells.