Side chain functionalization of cholesterol in the biosynthesis of solasodine in Solanum laciniatum

(25R)-26-Amino-cholesterol-[7α-³H], (25R)-26-amino-5-cholestene-3β,16β-diol-[7α-³H] and (25R)-26-acetylamino-5-cholestene-3β,16β-diol-[7α-³H] administered to Solanum laciniatum were converted into solasodine. The results indicate that in the biosynthesis of solasodine the introduction of nitrogen occurs immediately after the hydroxylation at C-26 and before a further oxidation of the side chain of cholesterol. The next step after the amination at C-26 is not hydroxylation at the 16β-position but probably the functionalization of C-22.     

One step synthesis of 6-oxo-cholestan-3β,5α-diol

Cholesterol metabolism has been recently linked to cancer, highlighting the importance of the characterization of new metabolic pathways in the sterol series. One of these pathways is centered on cholesterol-5,6-epoxides (5,6-ECs). 5,6-ECs can either generate dendrogenin A, a tumor suppressor present in healthy mammalian tissues, or the carcinogenic cholestane-3β,5α,6β-triol (CT) and its putative metabolite 6-oxo-cholestan-3β,5α-diol (OCDO) in tumor cells. We are currently investigating the identification of the enzyme involved in OCDO biosynthesis, which would be highly facilitated by the use of commercially unavailable [¹⁴C]-cholestane-3β,5α,6β-triol and [¹⁴C]-6-oxo-cholestan-3β,5α-diol. In the present study we report the one-step synthesis of [¹⁴C]-cholestane-3β,5α,6β-triol and [¹⁴C]-6-oxo-cholestan-3β,5α-diol by oxidation of [¹⁴C]-cholesterol with iodide metaperiodate (HIO₄).     

Hepatic microsomal conversion of pregnenolone to 3β,5,6β-trihydroxy-5α-pregnan-20-one via pregnenolone α- and β-epoxides

In the presence of ferrous ion, ADP, and an NADPH-generating system, [4-¹⁴C]pregnenolone was oxidized by bovine liver microsomes to its α-epoxide (5,6α-epoxy-3β-hydroxy-5α-pregnan-20-one), β-epoxide (5,6β-epoxy-3β-hydroxy-5β-pregnan-20-one), trihydroxypregnanone (3β,5,6β-trihydroxy-5β-pregnan-20-one) which were separated, isolated on an octadecylsilicone column in 70% aq. methanol by high performance liquid chromatography, identified with respective synthetic specimens by gas-liquid chromatography-mass spectrometry. The microsomal Δ⁵-oxidation products of pregnenolone were detected in trace yield either when EDTA was added to the incubation mixture or when ferrous ion was omitted from the mixture. The microsomal oxidation system generated malondialdehyde significantly. It, however, was retarded to a negligible extent either by the addition of EDTA or by the omission of ferrous ion. Therefore, the microsomal formation of the significant yields of Δ⁵-oxygenated pregnenolones was reasonably attributed to a reaction linked to microsomal lipid peroxidation. The ratio of pregnenolone α- to β-epoxides formed was 1:3. A comparable study carried out under the same conditions by using [4-¹⁴C]cholesterol as the substrate resulted in the similar Δ⁵-epoxidation with concomitant formation of cholestane-3β,5α,6β-triol; cholesterol α- and β-epoxides formed were in the ratio 1:4.Both pregnenolone α- and β-epoxides were hydrolyzed by the microsomes to trihydroxypregnanone as the sole metabolite at a relative rate of 0.6:1. A similar relative value was also obtained in the microsomal hydrolysis of cholesterol α- and β-epoxides to the cholestanetriol.     

Structural studies of the lipopolysaccharide of Moritella viscosa strain M2-226

The structure of the O-specific side chain of the lipopolysaccharide from the Gram-negative psychrophilic bacterium Moritella viscosa strain M2-226, responsible for the winter ulcer in Atlantic salmon, has been determined. Monosaccharide analysis and (1)H and (13)C NMR spectroscopy were employed to elucidate the structure. It was concluded that the polysaccharide is composed of a trisaccharide repeating unit with the following structure: →3)-β-D-GlcpNAc-(1→4)-[α-D-GlcpA-(1→3)]-α-L-Fucp-(1→ .     

UDP-glucuronosyltransferase-mediated metabolic activation of the tobacco carcinogen 2-amino-9H-pyrido[2,3-b]indole

2-Amino-9H-pyrido[2,3-b]indole (AαC) is a carcinogenic heterocyclic aromatic amine (HAA) that arises in tobacco smoke. UDP-glucuronosyltransferases (UGTs) are important enzymes that detoxicate many procarcinogens, including HAAs. UGTs compete with P450 enzymes, which bioactivate HAAs by N-hydroxylation of the exocyclic amine group; the resultant N-hydroxy-HAA metabolites form covalent adducts with DNA. We have characterized the UGT-catalyzed metabolic products of AαC and the genotoxic metabolite 2-hydroxyamino-9H-pyrido[2,3-b]indole (HONH-AαC) formed with human liver microsomes, recombinant human UGT isoforms, and human hepatocytes. The structures of the metabolites were elucidated by (1)H NMR and mass spectrometry. AαC and HONH-AαC underwent glucuronidation by UGTs to form, respectively, N(2)-(β-D-glucosidurony1)-2-amino-9H-pyrido[2,3-b]indole (AαC-N(2)-Gl) and N(2)-(β-D-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (AαC-HON(2)-Gl). HONH-AαC also underwent glucuronidation to form a novel O-linked glucuronide conjugate, O-(β-D-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (AαC-HN(2)-O-Gl). AαC-HN(2)-O-Gl is a biologically reactive metabolite and binds to calf thymus DNA (pH 5.0 or 7.0) to form the N-(deoxyguanosin-8-yl)-AαC adduct at 20-50-fold higher levels than the adduct levels formed with HONH-AαC. Major UGT isoforms were examined for their capacity to metabolize AαC and HONH-AαC. UGT1A4 was the most catalytically efficient enzyme (V(max)/K(m)) at forming AαC-N(2)-Gl (0.67 μl·min(-1)·mg of protein(-1)), and UGT1A9 was most catalytically efficient at forming AαC-HN-O-Gl (77.1 μl·min(-1)·mg of protein(-1)), whereas UGT1A1 was most efficient at forming AαC-HON(2)-Gl (5.0 μl·min(-1)·mg of protein(-1)). Human hepatocytes produced AαC-N(2)-Gl and AαC-HN(2)-O-Gl in abundant quantities, but AαC-HON(2)-Gl was a minor product. Thus, UGTs, usually important enzymes in the detoxication of many procarcinogens, serve as a mechanism of bioactivation of HONH-AαC.     

A convenient synthesis of the side chain of loteprednol etabonate--an ocular soft corticosteroid from 20-oxopregnanes using metal-mediated halogenation as a key reaction

A facile synthesis of the side chain of loteprednol etabonate, namely, chloromethyl-17α-[(ethoxycarbonyl))oxy]-11β-hydro of loteprednol etabonate, viz., chloromethyl-17α-[(ethoxycarbonyl))oxy]-11xy-3-oxoandrosta-1,4-diene-17β-carboxylate - an ocular soft corticosteroid, has been described starting from a 20-oxopregnane, namely, 3β-acetoxy-pregn-5(6),16(17)-diene-20-one (16-dehydropregnenolone acetate, i.e., 16-DPA) using our recently developed metal-mediated halogenation as a key reaction.     

The metabolism of cholesterol in the presence of liver mitochondria from normal and thyroxine-treated rats

1. [26-(14)C]- and [4-(14)C]-Cholesterol were incubated with liver mitochondria from normal and thyroxine-treated rats, and the radioactivity was measured in the carbon dioxide evolved during the incubation, in a butanol extract of the incubation mixture and in a volatile fraction containing substances of low molecular weight derived from the side chain of cholesterol. The butanol extract was separated by paper chromatography into three radioactive fractions, one of which contained the steroids more polar than cholesterol. 2. The butanol extract from incubations with [4-(14)C]cholesterol contained a radioactive substance moving with the same R(F) as cholic acid on thin-layer chromatography. 3. After incubation with [26-(14)C]-cholesterol, 60-80% of the radioactivity extracted by steam-distillation of the incubation mixture at acid pH was recovered as [(14)C]propionic acid. 4. In the presence of [26-(14)C]cholesterol, mitochondria from thyroxine-treated rats produced more radioactivity in carbon dioxide and in the volatile fraction, and less radioactivity in the fraction containing the polar steroids, than did mitochondria from normal rats. In the presence of [4-(14)C]cholesterol, mitochondria from thyroxine-treated rats produced the same amount of radioactivity in the polar steroids as did normal mitochondria. 5. Thyroxine treatment had no effect on the capacity of the mitochondria to oxidize propionate to carbon dioxide. 6. These results are best explained by supposing that thyroxine stimulates a rate-limiting reaction leading to the cleavage of the side chain of cholesterol, but has little or no influence on the hydroxylations of the ring system or on the oxidation of the C(3) fragment removed from the side chain.     

Effects of cholesterol side chain cleavage inhibitors on 11β-hydroxylation: linkage of mitochondrial oxygenase systems

Potent inhibitors of cholesterol side chain cleavage were tested for inhibition of 11β-hydroxylation of 11-deoxycortisol by bovine adrenal cortex mitochondria. Compounds which inhibited 11β-hydroxylation were metyrapone, 4-phenylimidazole, 1-benzylimidazole, 17β-ureido-1,4-androstadien-3-one, SU-8000, 4-methylaminoglutethimide, and 20α-hydroxycholestrol. Compounds which did not inhibit 11β-hydroxylation at concentrations of 0.5 mM were d-aminoglutethimide tartrate, 1-aminoglutethimide tartrate, N-methylaminoglutethimide, 16α-methylpregnenolone, 16β-methylpregnenolone, 20-tolylpregnenediol, 16α-chloropregnenolone-3-acetate, 16α-benzyloxypregnenolone-3-acetate and cyanoketone. The results obtained indicate that aminoglutethimide and its congeners, the 16-halogenated and 16-benzoylated derivatives of pregnenolone and cyanoketone are specific inhibitors of cholesterol side chain cleavage enzyme. The two mitochondrial steroid oxyganase systems are linked through their competition for a single electron source.     

Assay of liver microsomal cholesterol 7 alpha-hydroxylase using deuterated carrier and gas chromatography-mass spectrometry

The activity of cholesterol 7α-hydroxylase in rat liver microsomes was assayed by measuring the mass of 5-cholestene-3β, 7α-diol formed from endogenous cholesterol under standardized incubation conditions. After termination of incubations, a known amount of 5-[24,25,7β-²H₃]cholestene-3β,7α-diol was added. A chloroform extract of the incubation mixture was subjected to thin layer chromatography and the fraction containing 5-cholestene-3β,7α-diol was converted into trimethylsilyl ether. The trimethylsilyl ether was subjected to combined gas chromatography-mass spectrometry and the amount of unlabeled 5-cholestene-3β,7α-diol in the mixture was calculated from the ratio between the relative intensitics of the peaks at $\text{m}\text{e}$ 456 (M-90) and $\text{m}\text{e}$ 459 [M-(90 + 3)]. The precision of the method was ±2.2% (SD). The results with this method of assay of cholesterol 7α-hydroxylase were compared with those obtained with a method based on conversion of a trace amount of added [4-¹⁴C]cholesterol into 5-cholestene-3β,7α-diol.     

Side-chain conformers to allow conversion from normal to isoaspartate in age-related proteins and peptides

Dβ (or D-iso)- and Lβ- (or iso)- aspartyl (Asp) residues are accumulated in aged lens crystallins and amyloid beta (Aβ) proteins, respectively, as a result of spontaneous, nonenzymatic isomerization of normal Lα-Asp. To explore why such uncommon Asp isomers are accumulated, the stability of Lα-, Lβ-, and Dβ-Asp was compared in view of the staggered side-chain conformers. By using cylindrin (KVKVLGD⁷VIEV) from αB-crystallin and Aβ17-25 (L¹⁷VFF²⁰AED²³)VG²⁵) containing Asp isomers, the vicinal spin-spin coupling constants of Asp Hα-H_β1 and Hα-H_β2 were quantified by high-resolution solution ¹H NMR. It was found that the trans conformer was extremely preferred in Dβ-Asp7 side-chain of cylindrin. In Aβ17–25, the side chain of Lβ-Asp23 was likely to adopt trans conformer, while gauche conformers were rather rich in Lα-Asp23. In gauche conformers, the close distance between Asp carboxylate carbon (C_COO-) and backbone nitrogen (N) next to Asp is advantageous to the intramolecular cyclization to form succinimide intermediate, followed by the conversion from α- to β-Asp. The cyclization is limited in the trans conformer because of the long distance between C_COO- and N, to keep Dβ- or Lβ-Asp stable. This would be the reason for the site specificity of Asp isomerization in proteins. The higher population of trans conformer in Asp side chain, the less isomerization of Asp as shown as Asp76 in αA-crystallin. The stability and less reactivity of normal Asp and its isomers are the potential factors to determine whether or not the abnormal accumulation is permitted in aged crystallins and Aβ.     

Study on the Structure of a New Triterpene Saponin B from Polygala japoniea Houtt

A new triterpene saponin B has been isolated from the earial parts of Polygala japonica Houtt in folk-lore medicine. Its molecular: C48H78O20, m.p. 199–202℃, [α]D23+30.0 (C, 0.5, CH3OH). Acidic hydrolysis of this saponin gave a sapogenin (2α, 3α, 24-tri-hydroxyolean-12-ene-28-oic acid) and D-glucose. The structure of saponin B was elucidated as 28-O- [β-D-glucopyranosyl (1→2) -β-D-glucopyranosyl (1→2) -β-D-glucopy- ranosyl] 2α, 3α, 24-trihydroxyolean-12-ene-28-oic acid mainly by 13C-NMR, MS and some chemical transfomations.     

Use of 13C in biosynthetic studies. The labelling pattern in tenellin enriched from isotope-labelled acetate, methionine, and phenylalanine

The biogenetic origin of the carbon atoms in tenellin has been established by adding 13C-enriched compounds to cultures of Beauveria bassiana, and determining the isotopic distribution in the metabolite by 13C nuclear magnetic resonance spectrometry. Tenellin is formed by condensation of an acetate-derived polyketide chain with a phenylpropanoid unit that may be phenylalanine. Alternate carbon atoms of the polyketide chain were labelled with sodium [1(-13C)]- and [2-(13C]-acetate; sodium [1,2-(13C)]acetate was incorporated as intact two-carbon units, the presence of which in tenellin was apparent from coupling between adjacent 13C-enriched carbons. Substituent methyl groups of the polyketide-derived alkenyl chain were labelled with L-[Me-13C]methionine. The labelling patterns from DL-[carboxy-13C]phenylalanine and DL-[alpha-13C]phenylalanine indicated a rearrangement of the propanoid component at some stage in the synthesis. The mass spectrum of tenellin from cultures administered L-[15N]phenylalanine showed isotopic enrichment similar to that obtained with 13C- or 14C-labelled phenylalanine. During incorporation of L-[carboxy-14C, beta-3H]phenylalanine 96% of the tritium label was lost, discounting the possibility of a 1,2-hydride shift during biosynthesis of the metabolite.     

Perturbation of lipid metabolism by linoleic acid hydroperoxide in CaCo-2 cells

Dietary hydroperoxides are being discussed as potential health hazards contributing to oxidative stress-related diseases. However, how food-born hydroperoxides could exert systemic effects remains elusive in view of the limited chances to be absorbed. Therefore, the metabolic fate of 13-HPODE (13-hydroperoxy octadecadienoic acid), 13-HODE (13-hydroxy octadecadienoic acid) and linoleic acid (LA) was investigated in a CaCo-2 cell monolayer as a model of the intestinal epithelium. [1-14C]-13-HPODE, up to a non-cytotoxic concentration of 100 microM, did not cross the CaCo-2 cell monolayer unreduced if applied to the luminal side. The [1 -14C]-HPODE-derived radioactivity was preferentially recovered from intracellular and released diacylglycerols (DG), phospholipids (PL) and cholesterol esterified with oxidized fatty acids (oxCE). A similar distribution pattern was obtained with 13-HODE. In contrast, LA is preferentially incorporated into triacylglycerols (TG), cholesteryl esters (CE) and PL (but mainly released as TG). 13-HPODE dose-dependently decreased the incorporation of LA into released TG, while LA accumulated in cellular and released DGs, effects similarily exerted by 13-HODE. We concluded that food-born hydroperoxy fatty acids are instantly reduced by the gastrointestinal glutathione peroxidase, which was previously shown to persist in selenium deficiency. Accordingly, modulation of the glutathione peroxidases by selenium deprivation/repletion did not modify the disturbance of the lipid metabolism by 13-HPODE. Thus, hydroperoxy fatty acids disturb intestinal lipid metabolism by being esterified as hydroxy fatty acids into complex lipids, and may render lipoproteins synthesized thereof susceptible to further oxidative modifications.     

Inhibition of ACTH action on cultured bovine adrenal cortical cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin through a redistribution of cholesterol

The conversion of cholesterol to cortisol by cultured bovine adrenal cortical cells is stimulated 6-fold by adrenocorticotropin and is limited by the movement of cholesterol to the mitochondria (DiBartolomeis, M.J., and Jefcoate, C.R. (1984) J. Biol. Chem. 259, 10159-10167). Exposure of confluent cultures to the potent environmental toxicant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (10(-8)M), for 24 h prior to adrenocorticotropin (ACTH) addition decreased the rate of ACTH-stimulated steroidogenesis but did not affect the basal rate. TCDD was more effective against stimulation at 10(-11) M ACTH (4-fold) than at 10(-7) M ACTH (10%), consistent with an increase in EC50 for ACTH. Stimulation of bovine adrenal cortical cells by cAMP was similarly decreased by TCDD. In both cases the effectiveness of TCDD increased with time of exposure to the stimulant. The transfer of cholesterol to mitochondria in intact cells was quantitated by means of the 2-h accumulation of mitochondrial cholesterol in the presence of aminoglutethimide, an inhibitor of cholesterol side chain cleavage. Although cholesterol accumulated in the presence of ACTH (13 to 28 micrograms/mg), pretreatment of cells with TCDD caused a decrease in mitochondrial cholesterol (13 to 8 micrograms/mg). The effect of TCDD was produced relatively rapidly (t1/2 approximately 4 h). In absence of TCDD, the mitochondria of ACTH-stimulated cells also eventually lose cholesterol (after 2 h). It is concluded that TCDD pretreatment may increase the presence of a protein(s) that cause mitochondrial cholesterol depletion when the cells are stimulated by ACTH or cAMP. TCDD-enhanced cholesterol efflux from mitochondria diminishes cholesterol side chain cleavage when mitochondrial cholesterol is sufficiently depleted (after 2-4 h).     

Chemical lonization-mass spectrometric approach to structure determination of an intermediate in bile acid biosynthesis

In the course of a study on the details of the biosynthesis of cholic acid from cholesterol, 5β-[26,27-¹⁴C]cholestan-3α,7α,12α,24S,25-pentol, an intermediate in the 25-hydroxylation pathway of cholic acid, was incubated for 2 min with the cytosolic fraction of rat liver homogenate in the presence of NAD. A precursor to cholic acid which appeared to be a ketone was isolate from the reaction mixture by thin-layer chromatography. This material proved to be of inadequate volatility for electron impact mass spectrometry and was therefore studied, without further purification, by techniques of chemical ionization mass spectrometry using ammonia as the reagent gas. The spectrum was rerecorded using argon mixed with ammonia to induce additional fragmentation. One of these fragments corresponded to a McLafferty rearrangement of a 24-keto-25-hydroxycholestane derivative. To obtain additional evidence for this structure the following sequence of reactions was conducted on about 20 μg of the intermediate: (1) periodic acid oxidation, (2) diazomethane treatment, and (3) chromic acid oxidation. The change in molecular weight after each reaction agreed with the presence of a 25-hydroxy-24-keto side chain and three secondary hydroxyl groups in the molecule. Therefore, it could be deduced that the intermediate was 3α,7α,12α,25-tetrahydroxy-5β-cholestan-24-one. This work demonstrates that chemical ionization-mass spectrometic techniques can be a labor-saving alternative to other methods of structure determination and that 3α,7α,12α,25-tetrahydroxy-5β-cholestan-24-one is probably an intermediate in the 25-hydroxylation pathway of cholic acid from cholesterol.     

Azido analogs of neuroactive steroids

Analogs of pregnanolone (3α-hydroxy-5β-pregnan-20-one), modified in position 17 were prepared. Compounds with 20-keto pregnane side chain replaced completely by azide (17α- and 17β-azido-5β-androstan-3α-ol), compounds with its part replaced (20-azido-21-nor-5β-pregnan-3α-ol), and compounds with keto group only replaced ((20R)- and (20S)-20-azido-5β-pregnan-3α-ol) were synthesized using tosylate displacements with sodium azide or Mitsunobu reaction with azoimide. All five azido steroids were converted into corresponding sulfates. Subsequent tests for inhibition of glutamate induced response on NMDA receptors revealed that modification of pregnanolone sulfate side chain with azide did not disturb the activity and some of sulfates tested were more active than parent compound.     

Formation of 5α-dihydrotestosterone from 5α-androstane-3α,17β-diol in prostate cancer LAPC-4 cells – Identifying inhibitors of non-classical pathways producing the most potent androgen

5α-Dihydrotestosterone (5α-DHT) possesses a great affinity for the androgen receptor (AR), and its binding to AR promotes the proliferation of prostate cancer (PC) cells in androgen-dependent PC. Primarily synthesized from testosterone (T) in testis, 5α-DHT could also be produced from 5α-androstane-3α,17β-diol (3α-diol), an almost inactive androgen, following non-classical pathways. We reported the chemical synthesis of non-commercially available [4-¹⁴C]-3α-diol from [4-¹⁴C]-T, and the development of a biological assay to identify inhibitors of the 5α-DHT formation from radiolabeled 3α-diol in LAPC-4 cell PC model. We measured the inhibitory potency of 5α-androstane derivatives against the formation of 5α-DHT, and inhibition curves were obtained for the most potent compounds (IC₅₀ = 1.2–14.1 μM). The most potent inhibitor 25 (IC₅₀ = 1.2 μM) possesses a 4-(4-CF₃-3-CH₃O-benzyl)piperazinyl methyl side chain at C3β and 17β-OH/17α-CCH functionalities at C17 of a 5α-androstane core.     

Triterpene saponins from Cyclamen hederifolium

Five triterpene saponins never reported before, hederifoliosides A-E, and four known triterpene saponins were isolated from the tubers of Cyclamen hederifolium. The structures of hederifoliosides A-E were determined as 3β,16α-dihydroxy-13β,28-epoxyolean-30-oic acid 3-O-{[β-D-glucopyranosyl-(1 → 2)-O]-β-D-xylopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-(1 → 4)-O-α-L-arabinopyranoside}, 3β,16α-dihydroxy-13β,28-epoxyolean-30-oic acid 3-O-{[β-D-glucopyranosyl-(1 → 2)-O]-β-D-xylopyranosyl-(1 → 2)-O-[β-D-glucopyranosyl-(1 → 3)]-O-β-D-glucopyranosyl-(1 → 4)-O-α-L-arabinopyranoside}, 3β,16α-dihydroxy-13β,28-epoxyolean-30-al 3-O-{[β-D-glucopyranosyl-(1 → 2)-O]-β-D-xylopyranosyl-(1 → 2)-O-[β-D-glucopyranosyl-(1 → 3)]-O-[β-D-glucopyranosyl-(1 → 6)]-O-β-D-glucopyranosyl-(1 → 4)-O-α-L-arabinopyranoside}, 30-O-β-D-glucopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-3β,16α,30-trihydroxyolean-12-en-28-al 3-O-{[β-D-glucopyranosyl-(1 → 2)-O]-β-D-xylopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-(1 → 4)-O-α-L-arabinopyranoside}, 30-O-β-D-glucopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-3β,16α,28,30-tetrahydroxyolean-12-en 3-O-{[β-D-glucopyranosyl-(1 → 2)-O]-β-D-xylopyranosyl-(1 → 2)-O-[β-D-glucopyranosyl-(1 → 3)]-O-β-D-glucopyranosyl-(1 → 4)-O-α-L-arabinopyranoside}, by a combination of one- and two-dimensional NMR techniques, and mass spectrometry. The cytotoxic activity of the isolated compounds was evaluated against a small panel of cancer cell lines including Hela, H-446, HT-29, and U937. None of the tested compounds, in a range of concentrations between 1 and 50 μM, caused a significant reduction of the cell number.     

Steroidal saponins of Yucca filamentosa: Yuccoside C and protoyuccoside C

Two new saponins, yuccoside C and protoyuccoside C, have been isolated from the methanolic extract of Yucca filamentosa root and their structures elucidated. Yuccoside C is 3-O-[α-d-galactopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, whereas protoyuccoside C is 3-O-[α-d-galactopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosy]-(25S)-5β-furostan-3β,22α,26-triol.