Four new 3,5-cyclosteroidal saponins from Dracaena surculosa. (1/2)

Further search for steroidal compounds contained in Dracaena surculosa (Agavaceae) led to the isolation of two new 3,5-cyclospirostanol saponins (1, 2) and two new 3,5-cyclofurostanol saponins (3, 4). Their structural assignment was established by spectroscopic analysis and a few chemical transformations as (24S,25R)-1beta-[(beta-D-fucopyranosyl)oxy]-6beta-hydroxy-3alpha,5alpha-cyclospir ostan-24-yl beta-D-glucopyranoside (1), (24S,25R)-1beta-[(beta-D-glucopyranosyl)oxy]-6beta-hydroxy-3alpha,5alpha-cyclospi rostan-24-yl beta-D-glucopyranoside (2), (25S)-1beta-[(beta-D-glucopyranosyl)oxy]-6beta-hydroxy-22alpha-methoxy-3alpha,5al pha-cyclofurostan-26-yl beta-D-glucopyranoside (3), and (25S)-1beta-[(beta-D-fucopyranosyl)oxy]-6beta-hydroxy-22alpha-methoxy-3alpha,5alp ha-cyclofurostan-26-yl beta-D-glucopyranoside (4), respectively.  (+info)

S-adenosyl-L-methionine-cycloartenol methyltransferase activity in cell-free systems from Trebouxia sp. and Scenedesmus obliquus. (2/2)

1. Homogenates prepared from Trebouxia sp. 213/3 and Scenedesmus obliquus exhibited S-adenosyl-l-methionine-cycloartenol methyltransferase activity. 2. The products of the reaction, with cycloartenol as the substrate, were 24-methylenecycloartanol and cyclolaudenol. 3. Optimal enzyme activity was found in homogenates prepared at pH7.6 and the transmethylase was distributed between the supernatant and microsomal fractions of the Trebouxia homogenate. 4. The relevance of these results is discussed in relation to C(28) and C(29) sterol production in the algae.  (+info)