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PubMed1996

Synthetic Routes to a Constrained Ring Analog of Didemnin B.

The didemnin class of biologically active cyclodepsipeptides, isolated from a marine tunicate, has shown antitumor, antiviral, and immunosuppressive activities. Synthetic studies were undertaken to prepare a modified analog of one of the most potent congeners, didemnin B (1). The side chain of the isostatine unit was tethered into the macrocycle viaa cyclohexane ring in order to provide a more rigid conformation and determine the importance of this unit in bioactive compounds. This modification created a new macrocycle core and generated a diastereomeric mixture of a constrained analog of didemnin B (2).

Journal Article↗

PubMed1999

Enzymatic Lactonization Stategy for Enantioselective Synthesis of a Tetrahydrolipstatin Synthon.

A novel lipase-catalyzed protocol has been formulated for the simultaneous enantiocontrol of three stereogenic centers in a flexible acyclic system. This involved a porcine pancreatic lipase (PPL)-catalyzed delta-lactonization of a racemic 3,5-dihydroxy-2-alkyl ester to produce the lactone with high enantioselectivity (92.8%). The product lactone and its analogues are useful synthons for the asymmetric synthesis of various bioactive compounds, which include the potential anti-obesity compound, tetrahydrolipstatin.

Journal Article↗

PubMed2001

(+)-epi-Alpha-bisabolol [correction of bisbolol] is the wound-healing principle of Peperomia galioides: investigation of the in vivo wound-healing activity of related terpenoids.

Bioassay-guided investigation of the ethanol extract of Peperomia galioides using a tensile strength method in mice as a monitor led to the isolation of epi-alpha-bisabolol (1) (ED(50) 155 microg/mL). An in vivo healing study of selected commercially available monoterpenoids yielded two bioactive compounds, alpha-bisabolol (2) and alpha-terpineol (3) (ED(50) of 228 and 240 microg/g mouse[corrected], respectively).

3T3 Cells↗

PubMed2003

Three new cyclic peroxides from the marine sponge Plakortis aff simplex.

In our continuing program to identify bioactive compounds from marine invertebrates, the MeOH-EtOAc (1:1) extract of the sponge Plakortis aff simplex, collected in Madagascar, was found to be cytotoxic to a series of human tumor cells. From this sponge, three new compounds and one known one, two new 1,2-dioxane peroxylactones named plakortolides H (1) and I (2), and one new 1,2-dioxolane, designated andavadoic acid (3), have been isolated and their structures elucidated. In addition, the known N(3)-methyladenine (4) was isolated, to the best of our knowledge, for the first time from a marine source. Andavadoic acid (3) showed significant activity against 13 tumor cells with GI(50) values in the submicromolar range.

Animals↗

PubMed2003

Constituents from the stems of Aristolochia manshuriensis.

In a continuing search for bioactive compounds from Aristolochia species, 28 compounds, including three new constituents, demethylaristofolin E (1), aristomanoside (2), and dehydrooxoperezinone (3), were isolated from an extract of the stems of Aristolochia manshuriensis. The structures of these compounds were established by extensive 1D and 2D NMR spectral studies. Among these compounds, dehydrooxoperezinone (3) was found to inhibit the replication of HIV, with an EC(50) value of 17.5 microg/mL and a therapeutic index of 1.43.

Anti-HIV Agents↗

PubMed2006

A new route toward 7-Oxo-13-hydroxy-8,11,13-podocarpatrienes from labdane diterpenes.

Trinorlabdane 1,5-diketones (7, 10a,b, 13a,b), which are easily prepared from labdane diterpenes, are directly converted into the corresponding 7-oxo-13-hydroxy-8,11,13-podocarpatrienes, immediate precursors of bioactive compounds, under basic treatment. Utilizing this strategy, the first enantiospecific synthesis of 13-hydroxy-8,11,13-podocarpatriene (20), a constituent of Taiwania cryptomerioides, was achieved starting from (-)-sclareol (5) after a seven-step sequence in 55% overall yield.

Abietanes↗

PubMedDate not supplied

Metabolism of homoorientin by human intestinal bacteria.

As a part of our studies on the metabolism of bioactive compounds from oriental medicines by intestinal flora, homoorientin, a C-glycosylflavonoid, was anaerobically incubated with a human intestinal bacterial mixture. Homoorientin was transformed to 6-C-glucosyleriodictyol, (+/-)-eriodictyol, luteolin, 3,4-dihydroxyphenylpropionic acid, and phloroglucinol. A novel cleavage of the C-glycosyl bond was discovered for the first time by using intestinal bacteria.

Bacteria, Anaerobic↗

PubMedDate not supplied

Majorenolide and majorynolide: a new pair of cytotoxic and pesticidal alkene-alkyne delta-lactones from Persea major.

From the EtOH extract of the bark of Persea major, two bioactive compounds, majorynolide [1] and majorenolide [2], were isolated by activity-directed fractionation using brine shrimp. Their structures have been elucidated on the basis of spectral data as a pair of new alkene-alkyne delta-lactones, each with an exocyclic alkylidene methine carbon. Both 1 and 2 are moderately cytotoxic, and 2 is selectively pesticidal.

Animals↗

PubMed1992

Biologically active gamma-lactones and methylketoalkenes from Lindera benzoin.

Brine shrimp lethality-directed fractionation of the 95% EtOH extract of ripe berries from Lindera benzoin led to the isolation of three new C21 alkane-alkene gamma-lactones designated isolinderanolide, isolinderenolide, and linderanolide as well as the known series of C17 and C19 obtusilactones (isoobtusilactone A, obtusilactone A, isoobtusilactone, and obtusilactone) previously isolated from Lindera obtusiloba. The novel (6Z,9Z,12Z)-pentadecatrien-2-one, the known (6Z,9Z)-pentadecadien-2-one, and the known (+)-(Z)-nerolidol were also isolated as bioactive compounds. The structural elucidation and biological activities of these compounds are reported.

Animals↗

PubMed1992

Bioactive constituents from the twigs of Asimina parviflora.

The EtOH extract of Asimina parviflora (Annonaceae), when subjected to activity-directed fractionation using lethality to brine shrimp, led to the isolation and identification of five bioactive compounds: asimicilone [1], which is a new 2-quinolone alkaloid, 6-cis-docosenamide [2], which is a new amide of a long hydrocarbon chain fatty acid, and three known compounds, asimicin, (+)-syringaresinol, and beta-sitosterol-beta-D- glucopyranoside. The structure determination of the new alkaloid was performed by extensive nmr analyses, including HMQC and HMBC. Selective cytotoxic activities of these compounds in three human solid tumor cell lines are also reported.

Animals↗

PubMed1993

Bioactive metabolites from Sicilian marine fennel, Crithmum maritimum.

Bioactivity-guided fractionation of the lipid extract of Crithmum maritimum using the brine shrimp lethality assay led to the isolation of three bioactive compounds. Two of these are known C17 polyacetylenic metabolites, falcarinol [1] and falcarindiol [2], previously isolated from several species of the Umbelliferae and Araliaceae. The third active principle was identified as O-geranylvanillin [3], an aromatic ether described in the literature as a synthetic compound but unknown as a natural product. Cytotoxic activity of the pure compounds was significant for 1 and 2, much less intense for 3.

Alkynes↗

PubMed1993

Cytotoxic constituents from Hyptis verticillata.

A new cytotoxic (P-388 ED50 4 microgm/ml) arylnaphthalene lignan has been isolated from the Mexican medicinal plant Hyptis verticillata (Lamiaceae) and characterized as 5-methoxydehydropodophyllotoxin [1]. Eight additional lignans were also obtained by bioactivity-directed fractionation using the brine shrimp lethality test. Of these, the dehydro-beta-peltatin methyl ether 2 (P-388 ED50 1.8 microgm/ml) is reported for the first time as a natural product isolate. The other bioactive compounds were identified as dehydropodophyllotoxin [3], deoxydehydropodophyllotoxin [4]. (--)-yatein [5], 4'-demethyldeoxypodophyllotixin [6], isodeoxypodophyllotoxin [7], deoxypicropodophyllin [8], and beta-apopicropodophyllin [9]. Each of these compounds was evaluated against a panel of cell lines comprising a number of human cancer cell types [breast, colon, fibrosarcoma, lung, prostate, KB, and KB-VI (a multi-drug resistant cell line derived from KB)] and murine lymphocytic leukemia (P-388). Lignans 1-4 showed marginal cytotoxic activity against the human cell lines tested. In contrast, compounds 5-9 demonstrated a general nonspecific activity comparable to that of podophyllotoxin [12] (ED50 < 10-2 microgm/ml). In addition, the antimitotic potential of these compounds was determined in the astrocytoma (ASK) assay. Finally, the plant was also shown to contain the flavonoid sideritoflavone (KB ED50 1.6 microgm/ml) and the known pentacyclic triterpenoids ursolic, maslinic, 2 alpha-hydroxyursolic and oleanolic acids.

Animals↗

PubMed1994

Novel Ca(2+)-ATPase inhibitors from the dried root tubers of Polygonum Multiflorum.

The MeOH extract of the dried root tubers of Polygonum multiflorum yielded three bioactive compounds with an inhibitory activity on calmodulin-depleted erythrocyte calcium-dependent ATPase. These compounds were identified as E-2,3,5,4'-tetrahydroxystilbene 2-O-beta-D-glucopyranoside [2] (IC50 = 240 microM) and cis- and trans-E-3-butylidene-4,5,6,7-tetrahydro-6,7-dihydroxy-1(3H)- isobenzofuranone [3 and 4](IC50 = 160 and 260 microM, respectively). E-2,4,6,4'-Tetrahydroxystilbene 2-O-beta-D-glucopyranoside [1] was also isolated but was found to have no inhibitory effect on the enzyme.

Australia↗

PubMed1995

Identification of 3-hydroxy-3-methylglutaric acid (HMG) as a hypoglycemic principle of Spanish moss (Tillandsia usneoides).

Bioactivity-directed fractionation, using brine shrimp lethality and murine hypoglycemia, of an ethanol extract prepared from Tillandsia usneoides, led to the isolation of four apparently bioactive compounds from the water-soluble fraction. The compounds were identified as citric acid, succinic acid, 3-hydroxy-3-methylglutaric acid (HMG), and 3,6,3',5'-tetramethoxy-5,7,4'-trihydroxyflavone-7-O-beta-D-g lucoside. The brine shrimp lethality of the acids was simply due to acidity; however, HMG elicited significant hypoglycemic responses in fasting normal mice. Ethyl and methyl esters of citric acid were prepared and tested in the murine hypoglycemic assay. Five of the predominant sugars were identified by tlc. Free thymidine was also isolated. Further evaluation of HMG and other potential inhibitors of HMG CoA lyase, in the treatment of symptoms of diabetes mellitus, is suggested.

Animals↗

PubMed1997

New phomopsolides from a Penicillium sp.

Investigation of the bioactive compounds from a Penicillium sp. isolated from the inner bark of the Pacific yew, Taxus brevifolia, led to the isolation of the known furanone 1, and a series of phomopsolides. The phomopsolide fractions contained phomopsolides A and B, which have previously been described, and three new phomopsolides. The structures of the new phomopsolides were deduced by comparison of their NMR spectra to those of the known compounds.

Anti-Bacterial Agents↗

PubMed1998

Isolation and structure elucidation of new PKCalpha inhibitors from Pinus flexilis.

Bioassay-guided fractionation of the CH2Cl2-MeOH extract of Pinus flexilis using an assay for protein kinase C (PKC) inhibitory activity led to the isolation of the two new bioactive diarylheptanoids (3R)-1,7-bis(3, 4-dihydroxyphenyl)-3-(beta-D-glucopyranosyl)heptan-3-ol (1) and its aglycon (3R)-1,7-bis(3,4-dihydroxyphenyl)heptan-3-ol (2), together with the three known bioactive compounds, hirsutenone (3), oregonin (4), and hirsutanonol (5). The IC50 values of compounds 1-5 in the PKC assay were 1.4, 1.6, 1.4, 8.6, and 4.6 microg/mL, respectively.

Circular Dichroism↗

PubMed2000

Insecticidal and mutagenic evaluation of two annonaceous acetogenins.

Annonaceous acetogenins represent a new class of bioactive compounds whose primary mode of action is the inhibition of NADH-ubiquinone oxidoreductase. Given the potential pesticidal use of such a class of compounds, we have further evaluated the antifeedant and insecticidal effects of squamocin and annonacin, two annonaceous acetogenins, on Spodoptera littoralis, Leptinotarsa decemlineata, and Myzus persicae. Additionally, to partially assess their environmental risk, we have also tested their mutagenicity in Salmonella typhimurium strains TA98, TA100, and TA102 in the presence and absence of a metabolic activation system. Among the test compounds, annonacin showed antifeedant effects on L. decemlineata, while squamocin was toxic to L. decemlineata and M. persicae. Neither acetogenin was mutagenic, although both were toxic in the absence of a metabolic activation system. We compared these results with those obtained with rotenone, a well-known respiratory inhibitor that was highly toxic to L. decemlineata and M. persicae and showed no mutagenicity/toxicity in the S. typhimurium strains tested up to a concentration of 1000 microg per plate.

Animals↗

PubMed1997

Glucuronidation of entacapone, nitecapone, tolcapone, and some other nitrocatechols by rat liver microsomes.

PURPOSE: Nitrocatechol COMT inhibitors are a new class of bioactive compounds, for which glucuronidation is the most important metabolic pathway. The objective was to characterize the enzyme kinetics of nitrocatechol glucuronidation to improve the understanding and predicting of the pharmacokinetic behavior of this class of compounds. METHODS: The glucuronidation kinetics of seven nitrocatechols and 4-nitrophenol, the reference substrate for phenol UDP-glucuronosyltransferase activity, was measured in liver microsomes from creosote-treated rats and determined by non-linear fitting of the experimental data to the Michaelis-Menten equation. A new method that combined densitometric and radioactivity measurement of the glucuronides separated by HPTLC was developed for the quantification. RESULTS: Apparent K(m) values for the nitrocatechols varied greatly depending on substitution pattern being comparable with 4-nitrophenol (0.11 mM) only in the case of 4-nitrocatechol (0.19 mM). Simple nitrocatechols showed two-fold Vmax values compared with 4-nitrophenol (68.6 nmol min-1 mg-1), while all disubstituted catechols exhibited much lower glucuronidation rate. Vmax/K(m) values were about 10 times higher for monosubstituted catechols compared to disubstituted ones. The kinetic parameters for COMT inhibitors were in the following order: K(m) nitecapone > > entacapone > tolcapone; Vmax nitecapone > entacapone > tolcapone; Vmax/K(m) tolcapone > nitecapone > entacapone. CONCLUSIONS: Nitrocatechols can in principle be good substrates of UGTs. However, substituents may have a remarkable effect on the enzyme kinetic parameters. The different behaviour of nitecapone compared to the other COMT inhibitors may be due to its hydrophilic 5-substituent. The longer elimination half-life of tolcapone in vivo compared to entacapone could not be explained by glucuronidation kinetics in vitro.

Animals↗