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PubMed2001

Collinone, a new recombinant angular polyketide antibiotic made by an engineered Streptomyces strain.

Large chromosomal DNA fragments containing different parts of the putative rubromycin polyketide synthase gene cluster were cloned and functionally expressed in S. coelicolor CH999. Expression of these clones yielded 5 approximately 10 metabolites that were not detected in S. collinus culture extracts. This paper focusses on one of the new metabolites, termed collinone, that was isolated in large quantities and purified for spectroscopic structure determination and biological screening assays. Collinone is a heavily oxidized angular hexacyclic compound containing an unusual 1,4,5,8(2H,3H)-anthracenetetrone moiety previously only reported to be present in antibiotics SF2446A1, A2, A3, B1 and B2 isolated from Streptomyces sp. SF2446. Structure analysis of collinone indicates a tridecaketide with a 26 carbon backbone. The basic benz[a]naphthacene ring system of collinone is angular, similar to the aglycones of the well-known angucycline and angucyclinone antibiotics. While collinone showed antibacterial activity against vancomycin-resistant enterococci, no antifungal or significant antiviral activities were detected. Collinone could be a good starting point to obtain new bioactive angucyclin(on)e-like compounds by further genetic engineering of its pathway.

Anthracenes↗
PubMed2003

Synthesis and characterization of a macrocyclic near-infrared optical scaffold.

Macrocyclization of a bioactive peptide with a bifunctional near-infrared fluorescent optical probe gives a compound that retained the receptor binding affinity of the peptide and the photophysical properties of the optical probe. The robust nature of the new compound provides a structural framework for optimizing the activity of bioactive molecules and for monitoring chemical or biological processes in vivo and in vitro by near-infrared optical methods.

Cyclization↗
PubMed1996

N-nitroso compounds induce changes in carcinogen-metabolizing enzymes.

The bioactivation of N-nitrosoamines and polycyclic aromatic hydrocarbons (PAH) is mediated by the mixed function oxidase system, which includes dimethylnitrosamine N-demethylase I (DMN-dI), arylhydrocarbon hydroxylase (AHH), cytochrome P-450, cytochrome b5 and NADPH-cytochrome c reductase of liver microsomes. The present study shows the influence of N-nitroso compounds on the activities of the above-mentioned enzymes. Single-dose treatment (20 mg/kg body weight) of male mice with ethylbutylnitrosamine, propylbutylnitrosamine, or dibutylnitrosamine: increased (1) the activity of DMN-dI by 108%, 104%, 51%, respectively; (2) the cytochrome P-450 content by 106%, 72%, 51%, respectively; (3) the activity of AHH by 95%, 106%, 80% respectively; (4) the cytochrome b5 content by 164%, 97%, 94% respectively; and (5) decreased the activity of NADPH-cytochrome c reductase by 55%, 50% and 45%, respectively. Methylpropylnitrosamine decreased the activity of DMN-dI by 44% and the P-450 content by 50%. Diphenylnitrosamine also decreased cytochrome P-450 by 54%, AHH activity by 64% but increased the activity of DMN-dI by 42%, the cytochrome b5 content by 159% and NADPH-cytochrome c reductase activity by 57%. It seems from this study that the activity of AHH is dependent on P-450 content but DMN-dI is not since the compounds that increased or decreased the activity of AHH had parallel effects on P-450 content. Also, the extent to which the altered activities of DMN-dI, P-450, AHH, cytochrome b5 and NADPH-cytochrome c reductase depends on the type of alkyl groups linked to the nitroso group.

Animals↗
PubMed2004

De novo design, synthesis, and pharmacology of alpha-melanocyte stimulating hormone analogues derived from somatostatin by a hybrid approach.

A number of alpha-melanotropin (alpha-MSH) analogues have been designed de novo, synthesized, and bioassayed at different melanocortin receptors from frog skin (fMC1R) and mouse/rat (mMC1R, rMC3R, mMC4R, and mMC5R). These ligands were designed from somatostatin by a hybrid approach, which utilizes a modified cyclic structure (H-d-Phe-c[Cys---Cys]-Thr-NH(2)) related to somatostatin analogues (e.g. sandostatin) acting at somatostatin receptors, CTAP which binds specifically to micro opioid receptors, and the core pharmacophore of alpha-MSH (His-Phe-Arg-Trp). Ligands designed were H-d-Phe-c[XXX-YYY-ZZZ-Arg-Trp-AAA]-Thr-NH(2) [XXX and AAA = Cys, d-Cys, Hcy, Pen, d-Pen; YYY = His, His(1'-Me), His(3'-Me); ZZZ = Phe and side chain halogen substituted Phe, d-Phe, d-Nal(1'), and d-Nal(2')]. The compounds showed a wide range of bioactivities at the frog skin MC1R; e.g. H-d-Phe-c[Hcy-His-d-Phe-Arg-Trp-Cys]-Thr-NH(2) (6, EC(50) = 0.30 nM) and H-d-Phe-c[Cys-His-d-Phe-Arg-Trp-d-Cys]-Thr-NH(2) (8, EC(50) = 0.10 nM). In addition, when a lactam bridge was used as in H-d-Phe-c[Asp-His-d-Phe-Arg-Trp-Lys]-Thr-NH(2) (7, EC(50) = 0.10 nM), the analogue obtained is as potent as alpha-MSH in the frog skin MC1R assay. Interestingly, switching the bridge of 6 to give H-d-Phe-c[Cys-His-d-Phe-Arg-Trp-Hcy]-Thr-NH(2) (5, EC(50) = 1000 nM) led to a 3000-fold decrease in agonist activity. An increase in steric size in the side chain of d-Phe(7) reduced the bioactivity significantly. For example, H-d-Phe-c[Cys-His-d-Nal(1')-Arg-Trp-d-Cys]-Thr-NH(2) (24) is 2000-fold less active than 9. On the other hand, H-d-Phe-c[Cys-His-d-Phe(p-I)-Arg-Trp-d-Cys]-Thr-NH(2) (23) lost all agonist activity and became a weak antagonist (IC(50) = 1 x 10(-5) M). Furthermore, the modified CTAP analogues with a d-Trp at position 7 all showed weak antagonist activities (EC(50) = 10(-6) to 10(-7) M). Compounds bioassayed at mouse/rat MCRs displayed intriguing results. Most of them are potent at all four receptors tested (mMC1R, rMC3R, mMC4R, and mMC5R) with poor selectivities. However, two of the ligands, H-d-Phe-c[Cys-His-d-Phe-Arg-Trp-Pen]-Thr-NH(2) (9, EC(50) = 6.9 x 10(-9) M, 6.4 x 10(-8) M, 2.0 x 10(-8) M, and 1.4 x 10(-10) M at mMC1R, rMC3R, mMC4R, and mMC5R, respectively) and H-d-Phe-c[Cys-His(3'-Me)-d-Phe-Arg-Trp-Cys]-Thr-NH(2) (16, EC(50) = 3.5 x 10(-8) M, 3.1 x 10(-8) M, 8.8 x 10(-9) M, and 5.5 x 10(-10) M at mMC1R, rMC3R, mMC4R, and mMC5R, respectively) showed significant selectivities for the mMC5R. Worthy of mention is that neither of these two ligands is potent in the frog skin MC1R assay (EC(50) = 10(-7) M for 9 and EC(50) = 10(-5) M for 16). These results clearly demonstrated that binding behaviors in rodent MCRs are quite different from those in the classical frog skin (R pipiens) assay.

Animals↗
PubMed1994

Bioactivation of quinones by DT-diaphorase, molecular, biochemical, and chemical studies.

Because of the elevated DT-diaphorase (DTD) activity in certain tumors such as human nonsmall cell lung cancer (NCSLC), DTD is a potential target on which to base the development of new antitumor compounds. Mitomycin C is the most effective single agent used for the therapy of NSCLC and is metabolized and bioactivated by DTD. Mitomycin C is a poor substrate for DTD, however, and its metabolism is pH-dependent. We have therefore focused on identifying more efficient substrates for DTD. We have developed a metabolic and cytotoxicity screen that identifies compounds which are efficiently bioactivated by DTD. This screen utilizes both aerobic and hypoxic conditions and cell lines with both elevated and deficient DTD activity as an index of selectivity. Using the screen described above, we have identified [3-hydroxy-5-aziridinyl-1-methyl-2-(1H-indole-4,7-indione)-prop-be ta-en- alpha-ol] (E09), 2,5-diaziridinyl-1,4-benzoquinone (MeDZQ), and streptonigrin as compounds that are most efficiently bioactivated by DTD and exert selective cytotoxicity. Although certain tumors such as NSCLC have elevated DTD activity, we have characterized a point mutation at position 609 in the DTD cDNA, which codes for a proline to serine change in the protein and leads to a loss of enzyme activity. We have characterized this mutation in both BE human colon carcinoma cells and H596 human NSCLC cells. This mutation and resulting lack of DTD activity complicates the use of agents designed to target DTD in tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

The effect of angiotensin-converting enzyme inhibition on endothelial function and oxidant stress.

Angiotensin-converting enzyme (ACE) inhibitors effectively interfere with the renin-angiotensin system and exert various beneficial actions on vascular structure and function beyond their blood pressure-lowering effects. Data from experimental studies showed that angiotensin-converting enzyme inhibitors can attenuate the development of atherosclerosis in a wide range of species. The postulated mechanisms of this atheroprotective effect are the antioxidant actions of angiotensin-converting enzyme inhibitors and their enhancement of the endothelial elaboration of bioactive nitric oxide. The aim of this study was to assess the comparative effects of three angiotensin-converting enzyme inhibitors on endothelial nitric oxide production and action, and on endothelial oxidative stress. Using bovine aortic endothelial cells in culture grown to confluence, we examined the effects of 1, 10, 30 and 60 microM of each of captopril, zofenopril and enalapril on nitrite/nitrate accumulation in the media, cyclic GMP accumulation in the cell lysate, and F(2)-isoprostanes in lipid extracts from the cells. Results showed that the sulfhydryl angiotensin-converting enzyme inhibitor zofenopril has unique properties compared with captopril and enalapril. This compound improves nitric oxide production and bioactivity, and does so in conjunction with decreased endothelial cell oxidant stress. The biochemical basis for this protective mechanism is not entirely clear; however, these actions suggest that zofenopril may reduce endothelial effects of risk factors for atherothrombotic disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2002

Microbial technologies for the discovery of novel bioactive metabolites.

Soil microbes represent an important source of biologically active compounds. These molecules present original and unexpected structure and are selective inhibitors of their molecular targets. At Biosearch Italia, discovery of new bioactive molecules is mostly carried out through the exploitation of a proprietary strain collection of over 50000 strains, mostly unusual genera of actinomycetes and uncommon filamentous fungi. A critical element in a drug discovery based on microbial extracts is the isolation of unexploited groups of microorganisms that are at the same time good producers of secondary metabolites. Molecular genetics can assist in these efforts. We will review the development and application of molecular methods for the detection of uncommon genera of actinomycetes in soil DNA and for the rapid dereplication of actinomycete isolates. The results indicate a substantial presence in many soils of the uncommon genera and a large diversity of isolated actinomycetes. However, while uncommon actinomycete strains may provide an increased chance of yielding novel structures, their genetics and physiology are poorly understood. To speed up their manipulation, we have developed vectors capable of stably maintaining large segments of actinomycete DNA in Escherichia coli and of integrating site specifically in the Streptomyces genome. These vectors are suitable for the reconstruction of gene clusters from smaller segment of cloned DNA, the preparation of large-insert libraries from unusual actinomycete strains and the construction of environmental libraries.

Actinobacteria↗
PubMed2004

Total synthesis and biological evaluation of a C(10)/C(12)-phenylene-bridged analog of epothilone D.

The total synthesis of compound 8, a conformationally constrained analog of epothilone D (2), has been achieved through a convergent strategy based on three key fragments comprising C(1)-C(6) (26), C(7)-C(12) (16), and C(13)-O(16) (19) of the macrocyclic framework. Construction of the C(12)-C(13) bond involved Pd(0)-mediated B-alkyl Suzuki coupling between aryl bromide 16 and olefin 19, and proceeded in excellent yield, while formation of the C(6)-C(7) bond through aldol reaction was somewhat less efficient. Surprisingly, macrolactonization was rather low-yielding and gave protected 8 only in 39% yield. Although 8 had been suggested by pharmacophore modeling to adopt a conformation similar to the bioactive conformation of epothilone B, the compound was devoid of any significant antiproliferative activity.

Drug Evaluation, Preclinical↗
PubMed1993

Rationale for the use of aliphatic N-oxides of cytotoxic anthraquinones as prodrug DNA binding agents: a new class of bioreductive agent.

NAD(P)H dependent cytochrome P450's and other haemoproteins under hypoxia, mediate two-electron reduction of a wide range of structurally dissimilar N-oxides to their respective tertiary amines. Metabolic reduction can be utilised, in acute and chronic hypoxia, to convert N-oxides of DNA affinic agents to potent and persistent cytotoxins. In this respect a knowledge of N-oxide bioreduction and the importance of the cationic nature of agents that bind to DNA by intercalation can be combined to rationalise N-oxides as prodrugs of DNA binding agents. The concept is illustrated using the alkylaminoanthraquinones which are a group of cytotoxic agents with DNA binding affinity that is dependent on the cationic nature of these compounds. The actions of the alkylaminoanthraquinones involve drug intercalation into DNA (and double stranded RNA) and inhibition of both DNA and RNA polymerases and topoisomerase Type I and II. A di-N-oxide analogue of mitoxantrone, 1,4-bis([2-(dimethylamino-N-oxide)ethyl]amino)5,8-dihydroxyanthracene -9,10- dione (AQ4N) has been shown to possess no intrinsic binding affinity for DNA and has low toxicity. Yet in the absence of air AQ4N can be reduced in vitro to a DNA affinic agent with up to 1000-fold increase in cytotoxic potency. Importantly the reduction product, AQ4, is stable under oxic conditions. Studies in vivo indicate that antitumour activity of AQ4N is manifest under conditions that promote transient hypoxia and/or diminish the oxic tumour fraction. The advantage of utilising the reductive environment of hypoxic tumours to reduce N-oxides is that, unlike conventional bioreductive agents, the resulting products will remain active even if the hypoxia that led to bioactivation is transient or the active compounds, once formed, diffuse away from the hypoxic tumour regions. Furthermore, the DNA affinic nature of the active compounds should ensure their localisation in tumour tissue.

Animals↗
PubMed1996

Protective effects of garlic and related organosulfur compounds on acetaminophen-induced hepatotoxicity in mice.

In previous studies, we have demonstrated that diallyl sulfide, a flavor component of garlic, protects against chemically induced hepatotoxicity. The present study examined the activities of fresh garlic homogenates (FGH) and related organosulfur compounds in the protection against acetaminophen (APAP)-induced hepatotoxicity and the possible mechanisms involved in this protection. When FGH (5 g/kg) was administered to Swiss-Webster mice 2 hr prior to, or immediately after, an APAP treatment (0.2 g/kg), APAP-induced hepatotoxicity was essentially prevented as indicated by serum levels of alanine aminotransferase and lactate dehydrogenase and by liver histopathology. Partial protection was observed with a lower dose of FGH (0.5 g/kg). FGH also prevented APAP-induced hepatic glutathione depletion in a dose-dependent manner. FGH significantly inhibited the formation of APAP-oxidized metabolites, as indicated by decreased plasma levels of oxidized APAP metabolites. The amount of APAP excreted as oxidized metabolites in the 24 hr urine samples was also significantly lower in the mice pretreated with FGH. FGH supernatant inhibited cytochrome P450-dependent APAP oxidation in microsomal incubations. The results suggest that the protection against APAP-induced hepatotoxicity by FGH is mainly due to its inhibition of P450-mediated APAP bioactivation. Several garlic-derived organosulfur compounds and structurally related compounds were examined for their abilities to protect against APAP-induced hepatotoxicity. An S-allyl structure appears to be a common feature for most sulfides to inhibit P450 2E1-dependent activity and to display good protective activities.

Acetaminophen↗
PubMed2004

Detection of glutathione conjugates derived from 4-ipomeanol metabolism in bile of rats by liquid chromatography-tandem mass spectrometry.

Earlier studies postulated that bioactivation of 4-ipomeanol by cytochrome P450 enzymes may occur through oxidation of its furan ring, following a mechanism similar to the bioactivation of other furan-containing compounds. This would lead to the formation of furan epoxides and alpha,beta-unsaturated di-aldehyde-reactive metabolites that can conjugate with glutathione. These metabolites are thought to be responsible for the cytotoxic and anticancer properties of 4-ipomeanol. We hypothesized that if 4-ipomeanol is metabolized following this pathway, its glutathione conjugates would be isobaric (molecular ion mass = 492 Da) and would be excreted in bile. To investigate this hypothesis, we analyzed by liquid chromatography-tandem mass spectrometry the bile of rats administered d0/d6 4-ipomeanol (1:1 ratio) intravenously. Hexadeuterated 4-ipomeanol had all deuterium atoms incorporated on its aliphatic chain. Multiple reaction monitoring scans of bile for the mass transition: MH+/(MH - 129)+, which is characteristic of glutathione conjugates, detected four glutathione conjugates. The observation of the isotope cluster (M + 1)+ (d0)/(MH + 6)+ (d6) in a 1:1 molar ratio confirmed that these conjugates were derived from 4-ipomeanol. Retention of the six deuterium atoms in the glutathione conjugates detected, (MH + 6)+, indicates that the bioactivation of 4-ipomeanol took place on the furan ring moiety. Rat hepatic microsomal incubations provided additional evidence. From this study, the mass of the reactive metabolites of 4-ipomeanol can be inferred. The inferred mass (186 Da) matches the mass postulated. A pathway of 4-ipomeanol bioactivation is proposed here. This work represents one step forward to understanding the mechanism of bioactivation of 4-ipomeanol.

Animals↗
PubMed2001

Bioavailability of flavan-3-ols and procyanidins: gastrointestinal tract influences and their relevance to bioactive forms in vivo.

There is considerable interest in the bioavailability of flavan-3-ols such as tea catechins and cocoa-derived procyanidin components of the diet and their bioactivity in vivo. Their hydrogen-donating abilities and their propensity for nitration make these compounds powerful scavengers of reactive oxygen and nitrogen species. In addition, recent evidence has suggested that these compounds may interact with redox-sensitive cell signaling pathways. However, their bioactivity in vivo will be dependent on the absorption and metabolism of these compounds after ingestion and the reducing properties of resulting metabolites. Many cell, animal, and human studies have shown that flavanol monomers, such as epicatechin, are extensively metabolised to O-methylated forms and/or conjugated to glucuronides and sulphates during absorption into the circulation. The cleavage of higher procyanidin oligomers to mixtures of monomer and dimer in the stomach may act to enhance the potential for their absorption in the small intestine as higher oligomers have very limited absorption. Studies suggest that the major bioactive forms of flavanol monomers and procyanidins in vivo are likely to be metabolites and/or conjugates of epicatechin. One such metabolite, 3'-O-methylepicatechin, has been shown to exert protective effects against oxidative stress-induced cell death. Future studies will continue to concentrate on the exact mechanism of action of the bioactive forms of flavan-3-ols in vivo.

Animals↗
PubMed2005

In vivo bioassay-guided fractionation of marine sediment extracts from the Southern California Bight, USA, for estrogenic activity.

The exposure and uptake of environmental estrogenic compounds have been reported in previous studies of demersal flatfish species in the central Southern California Bight (SCB), USA. The objective of this study was to evaluate the estrogenic or feminizing activity of marine sediments from the SCB by using in vivo vitellogenin (VTG) assays in male or juvenile fish. In 2003, sediments were collected near wastewater outfalls serving the counties of Los Angeles (LACSD) and Orange (OCSD), and the city of San Diego (SD), California, USA. Cultured male California halibut (CH; Paralichthys californicus) were either directly exposed to sediments for 7 d or treated with two intraperitoneal injections of sediment extract over 7 d. The 17beta-estradiol (E2) equivalent values ranged from 1 to 90 microg/kg with LACSD > SD > OCSD. Measurable concentrations of E2 were observed in all sediment extracts and ranged from 0.16 to 0.45 ng/g. Estrone (El) was only observed in sediments near the LACSD outfall (0.6 ng/g). Alkylphenols and alkylphenol ethoxylates were observed in all sediment samples, but were highest near the OCSD outfall, where concentrations of nonylphenol were 3,200 ng/g. Fractionation studies of the LACSD sediment extract collected in 2004 failed to demonstrate relationships between VTG expression and 62 analytes, including E2, which was observed in the whole extract (2.9 ng/g). Oxybenzone (1.6 ng/g) was identified in bioactive fractions as well as unknown compounds of relatively high polarity. These results indicate that estrogen receptor-based assays may underestimate environmental estrogenic activity and estrogenic compounds other than classic natural and xenoestrogens may contribute to estrogenic activity of sediments from the SCB.

Animals↗
PubMed1999

Purification of cytosolic beta-glucosidase from pig liver and its reactivity towards flavonoid glycosides.

Flavonoid glycosides are common dietary components which may have health-promoting activities. The metabolism of these compounds is thought to influence their bioactivity and uptake from the small intestine. It has been suggested that the enzyme cytosolic beta-glucosidase could deglycosylate certain flavonoid glycosides. To test this hypothesis, the enzyme was purified to homogeneity from pig liver for the first time. It was found to have a molecular weight (55 kDa) and specific activity (with p-nitrophenol glucoside) consistent with other mammalian cytosolic beta-glucosidases. The pure enzyme was indeed found to deglycosylate various flavonoid glycosides. Genistein 7-glucoside, daidzein 7-glucoside, apigenin 7-glucoside and naringenin 7-glucoside all acted as substrates, but we were unable to detect activity with naringenin 7-rhamnoglucoside. Quercetin 4'-glucoside was a substrate, but neither quercetin 3, 4'-diglucoside, quercetin 3-glucoside nor quercetin 3-rhamnoglucoside were deglycosylated. Estimates of K(m) ranged from 25 to 90 microM while those for V(max) were about 10% of that found with the standard artificial substrate p-nitrophenol glucoside. The non-substrate quercetin 3-glucoside was found to partially inhibit deglycosylation of quercetin 4'-glucoside, but it had no effect upon activity with p-nitrophenol glucoside. This study confirms that mammalian cytosolic beta-glucosidase can deglycosylate some, but not all, common dietary flavonoid glycosides. This enzyme may, therefore, be important in the metabolism of these compounds.

Animals↗
PubMed1994

Effects of deuterium labeling on azido amino acid mutagenicity in Salmonella typhimurium.

The mutagenic effects of azide (N3-) anion in bacterial test systems require the formation of the novel mutagenic metabolite, 3-azido-L-alanine (AZAL). Although the mechanism of AZAL-induced mutagenicity is unknown, subsequent bioactivation of this metabolite appears likely. Earlier studies have shown that other azide-containing amino acids are mutagenic as well. In fact, the mutagenic potency of the synthetic AZAL homologue, L-2-amino-4-azidobutanoic acid (HomoAZAL), was several times that of AZAL. To gain insight into the biochemical processing and mutagenicity of azido amino acids in Salmonella typhimurium, several specifically deuterium-labeled azido amino acids have been prepared and tested for mutagenic potency. In addition, the effect of (aminooxy)acetic acid (AOA) (a potent inhibitor of pyridoxal-dependent processes) on AZAL-induced mutagenesis was examined. The results showed that 2-deuterium substitution of AZAL resulted in a slight increase in mutagenic potency, while AOA treatment resulted in no change in AZAL potency. Taken together these findings did not support the involvement of pyridoxal-dependent processes in AZAL bioactivation. In contrast, deuterium substitution adjacent to the azide group in HomoAZAL and 5-azido-L-norvaline (N3-Norval) resulted in a large decrease in mutagenic potency when compared to the non-deuterium labeled compounds. These observations are consistent with a bioactivation mechanism involving rate-limiting C-H bond cleavage in the formation of the ultimate mutagen. Moreover, this effect of deuterium labeling points to processing of the azide-containing side chain as a key feature in the mutagenic activation mechanism.

Alanine↗
PubMed2005

Antioxidant properties of palm fruit extracts.

Phenolic compounds have been shown to exhibit bioactive properties, and in particular antioxidant effects. A phenolic-rich fraction has been isolated from the aqueous by-product obtained during the milling of oil palm fruits. The objectives of the study were to determine the phenolic content of the crude and ethanolic extracts of oil palm fruits and to evaluate the antioxidant properties of these extracts. The total phenolics content of the crude and ethanol extracts as determined by the Folin-Ciocalteu method were found to be 40.3 +/- 0.5 and 49.6 +/- 0.6 mg GAE/g extract (dry basis), respectively. The radical scavenging activity of the extracts determined using 2,2 diphenyl-1-picrylhydrazyl radical (DPPH.) indicated that both crude and ethanol extracts exhibit hydrogen-donating capacity, and have antiradical power (ARP) comparable to ascorbic acid. The DPPH radical scavenging activity of the extracts were less than that of gallic acid, but the time-course variations of the scavenging curves suggest that the extracts acted by a mechanism similar to that of gallic acid. The electron-donating potentials of the extracts were inferred from the hydrogen peroxide scavenging and reducing power assays. The reducing power of crude and ethanol extracts at 1 mM GAE were found to be comparable to that of 0.3 mM gallic acid. The extracts indicated complete scavenging of hydrogen peroxide at concentrations above 0.4 mM GAE. These findings suggest that the crude and ethanol extracts are able to scavenge free radicals, by either hydrogen or electron donating mechanisms, and can therefore act as primary antioxidants.

Antioxidants↗
PubMed2005

Multi-component HPLC fingerprinting of Radix Salviae Miltiorrhizae and its LC-MS-MS identification.

The multi-component fingerprinting method of Radix Salviae Miltiorrhizae (Root of Salvia miltiorrhiza BGE.), an important and popular medicinal herb in traditional Chinese medicine, was studied using reverse-phase HPLC and LC-MS-MS. Extract containing both the water-soluble phenolic compounds and nonpolar diterpenoid compounds known to be the herb's main bioactive components was prepared by a two-step extractive procedure. An HPLC fingerprinting method which can simultaneously separate these two types of compounds was established with gradient elution mode and photodiode array detection at 280 nm. Eighteen peaks in this HPLC fingerprint were structurally identified by employing LC-MS-MS techniques. The electrospray ionization (ESI) MS-MS spectra of most salvianolic acids displayed a characteristic behavior of loss of danshensu and caffeic acid moieties, while those of tanshinones showed a particular behavior of loss of H2O which is quite different from the fragmentation pattern in electron ionization mass spectrometry (EI-MS). The HPLC fingerprints of 7 batches of crude drugs showed similar separation pattern and provided much chemical information of the pharmacologically-active compounds in the crude drugs, which is useful for the authentication and quality evaluation of this medicinal herb.

Chromatography, High Pressure Liquid↗
PubMed1998

Variation of oxide films on titanium induced by osteoblast-like cell culture and the influence of an H2O2 pretreatment.

Variations of titanium oxide films induced by osteoblast-like cells in a rat calvaria culture system and the influence of an H2O2 pretreatment have been investigated by using X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. For abraded titanium, the results revealed that phosphate and calcium ions may incorporate into the surface oxide film during the cell culture, forming a precipitate with a Ca/P ratio near that of hydroxyapatite. Oxidized carbon also was found in the surface layer, most likely precipitated hydroxylcarbonated apatite (HCA). The H2O2 pretreatment of titanium in a phosphate-buffered saline solution results in a 10-fold thickened porous oxide film and large amounts of surface hydroxyl groups as well as a certain amount of phosphate ions inside the oxide film. During the cell culture, the H2O2-treated titanium surface favors the ion incorporation and precipitation of the HCA-like compound, which probably is inlaid into the oxide film. Osteoblast-like cells on the H2O2-treated titanium showed a more active morphology during the initial stage compared with cells on abraded titanium. Moreover, bone-like nodule formation and mineralization appear to be related to the precipitation of the HCA-like compound on the surface. The results are discussed with respect to corrosion resistance, ion incorporation and precipitation of the HCA-like compound on the surface, osseointegration, and bioactivity of titanium implants.

Animals↗