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At least 19 recordsLinked to original sources
PubMed2002

Four new 3,5-cyclosteroidal saponins from Dracaena surculosa.

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-cyclospirostan-24-yl beta-D-glucopyranoside (1), (24S,25R)-1beta-[(beta-D-glucopyranosyl)oxy]-6beta-hydroxy-3alpha,5alpha-cyclospirostan-24-yl beta-D-glucopyranoside (2), (25S)-1beta-[(beta-D-glucopyranosyl)oxy]-6beta-hydroxy-22alpha-methoxy-3alpha,5alpha-cyclofurostan-26-yl beta-D-glucopyranoside (3), and (25S)-1beta-[(beta-D-fucopyranosyl)oxy]-6beta-hydroxy-22alpha-methoxy-3alpha,5alpha-cyclofurostan-26-yl beta-D-glucopyranoside (4), respectively.

Cyclosteroids↗
PubMed2003

Neurosteroid analogues. 9. Conformationally constrained pregnanes: structure-activity studies of 13,24-cyclo-18,21-dinorcholane analogues of the GABA modulatory and anesthetic steroids (3alpha,5alpha)- and (3alpha,5beta)-3-hydroxypregnan-20-one.

The hydrogen-bond-acceptor properties of the carbonyl moiety in the 17beta-acetyl group on the D-ring of the anesthetic steroids (3alpha,5alpha)- and (3alpha,5beta)-3-hydroxypregan-20-one form an important part of the anesthetic steroid pharmacophore. 13,24-Cyclo-18,21-dinorcholanes containing a ketone or conjugated ketone group at C-20, C-22, C-23, or C-24 were prepared as conformationally constrained analogues of these anesthetic steroids and were used to probe for alternate locations for the D-ring hydrogen-bond-accepting carbonyl group. The analogues were evaluated (1). in [(35)S]-tert-butylbicyclophosphorothionate binding experiments, (2). in electrophysiological experiments using rat alpha(1)beta(2)gamma(2L) GABA(A) receptors expressed in Xenopus laevis oocytes, and (3). as tadpole anesthetics. In the binding assay, the relative order of potencies for the analogues in the 5alpha- and 5beta-series is identical. For the ketones, the order is 24-one >or= 23-one > 20-one > 22-one. Likewise, for the enones, the order is delta(22)-24-one > delta(20(22))-23-one > delta(22)-20-one > delta(23)-22-one. Similar relative orders of potencies are also found in the other two bioassays. The activities of the 24-one and delta(22)-24-one compounds were expected to be very low, because the carbonyl group in these compounds is located over the steroid C-ring and oriented toward C-8. Instead, these compounds have the highest activities in their respective series, with the delta(22)-24-one compounds having activities comparable to those of the reference anesthetic steroids. The electrophysiology results obtained with the 24-oxo-cyclosteroids suggest that rat alpha(1)beta(2)gamma(2L) GABA(A) receptors contain more than one donor for the hydrogen-bond-acceptor group of anesthetic steroids. The family of cyclosteroids should be useful for future structure-activity relationship studies of steroid modulation of other GABA(A) receptor subtypes.

Anesthetics↗
PubMed2003

Cytotoxic constituents of Brachistus stramoniifolius.

Phytochemical investigation of Brachistus stramoniifolius (Kunth) Miers (formerly Witheringia stramoniifolia Kunth) (Solanaceae) was initiated following primary biological screening and in view of the absence of prior phytochemical studies conducted on this species. Fractionation of an ethyl acetate extract from the roots of the plant, guided by in vitro cytotoxic activity using cultured KB (human nasopharyngeal carcinoma) cells, led to the isolation of three known compounds of the 13,14-seco-16,24-cyclosteroid type, physalins B (1), F (2) and H (3). Their structures were characterized by comparison of their physical and spectral data to published values, with 1D- and 2D-NMR experiments being performed to assure unambiguous resonance assignments. Biological evaluation of these three compounds against a panel of human and murine cancer cell lines demonstrated their broad cytotoxic activity.

Antineoplastic Agents, Phytogenic↗
PubMed1981

A ring contraction of 18,20-cyclo-steroids. Preparation of 18-acetyl-17,18-cyclo-4-androsten-3-one and 18-hydroxyacetyl-17,18-cyclo-4-androsten-3-one.

The ring contraction of 18 alpha-mesyloxy-20 alpha-hydroxy-18,20-cyclopregn-4-en-3-one (Ib) and 18 alpha-mesyloxy-20 alpha-hydroxy-21-acetyloxy-18,20-cyclo-pregn-4-en-3-one (Id) took place upon exposure to Florisil at 25 degrees C, producing 18 alpha-acetyl-17,18-cycloandrost-4-en-3-one (IIa) and 18 alpha-acetoxyacetyl-17,18-cycloandrost-4-en-3-one (IIb) respectively. A similar ring contraction of 18 alpha, 20 alpha-dihydroxy-18,20-cyclopregn-4-en-3-one (Ia) took place upon electron impact. Deuterium labeling demonstrated that the first steps of mass spectral fragmentation of Ia were the rearrangement to IIa and the oxidative cleavage to 3,18,20-trioxo-4-pregnene (IVa).

Androstenes↗