Presence of Fatty Acid Synthase Inhibitors in the Rhizome of Alpinia officinarum Hance

The galangal (the rhizome of Alpinia officinarum, Hance) is popular in Asia as a traditional herbal medicine. The present study reports that the galangal extract (GE) can potently inhibit fatty-acid synthase (FAS, E.C.2.3.1.85). The inhibition consists of both reversible inhibition with an IC50 value of 1.73?μg?dried?GE/ml, and biphasic slow-binding inactivation. Subsequently the reversible inhibition and slow-binding inactivation to FAS were further studied. The inhibition of FAS by galangin, quercetin and kaempferol, which are the main flavonoids existing in the galangal, showed that quercetin and kaempferol had potent reversible inhibitory activity, but all three flavonoids had no obvious slow-binding inactivation. Analysis of the kinetic results led to the conclusion that the inhibitory mechanism of GE is totally different from that of some other previously reported inhibitors of FAS, such as cerulenin, EGCG (epigallocatechin gallate) and C75.     

Evaluation of the inhibitory activities of aceraceous plants on fatty acid synthase

Fatty acid synthase (FAS) is a very significant lipogenic enzyme participating in energy metabolism in vivo and has been reported as a potential new therapeutic target for cancer treatment. The extracts from sixteen Aceraceae were prepared to assay their inhibitory activities against duck liver FAS and their correlated antitumor bioactivity. Their inhibition of FAS was composed of a reversible fast-binding inhibition, by which 0.41 microg/mL of the A. campestre extract inhibits 50% FAS activity, and an irreversible slow-binding inhibition with inactivation rate constants, k(obs), ranging between 1.5 x 10(-3) and 10.6 x 10(-3) min(-1). Three Aceraceae extracts were selected from their smaller IC50 values to study different type of inhibitions against the three substrates in the FAS overall reaction. As compared with other reported FAS inhibitors including EGCG with regard to inhibition constant and IC50 value, the extracts appeared to be more efficient inhibitors, and exhibited a considerable inhibition against the growth of five types of cancer cells (China patent application number 200610088901.6), which may be related to the inhibition of lipogenesis in these cells.     

Influence of dietary flavonoids on the glycation of plasma proteins

It has been suggested that the increasing glycation in diabetes can influence the ability of plasma proteins to bind to small molecules. Herein, the influence of flavonoids on the glycation of plasma proteins was investigated. After being incubated with glucose at 37 °C, the levels of glycated albumin (HGA) were significantly improved in healthy human plasma proteins (HPP). The inhibitory effects of flavonoids against the formation of advanced glycation products (AGEs) in HPP were determined as: galangin > apigenin > kaempferol ≈ luteolin > myricetin > quercetin. After being combined with 20 μmol L?1 of quercetin for 11 days, the fresh plasma with δ-glucose caused 323.05-32.07% inhibition of HGA formation in type II diabetes plasma proteins (TPP). Luteolin showed weak inhibition of HGA formation in TPP. However, kaempferol, galangin and apigenin hardly inhibited the formation of HGA in TPP. These results showed that more hydroxyl groups on ring B of flavonoids will enhance the inhibitory effects on the HGA formation in TPP.     

The extract of leaves of Acer truncatum Bunge: A natural inhibitor of fatty acid synthase with antitumor activity

Fatty acid synthase (FAS) has been identified as a potential antitumor target. The extract from the leaves of Acer truncatum Bunge (Extr) was prepared to assay its inhibitory activity against FAS, which was isolated from duck liver, and the correlated antitumor bioactivity. Its inhibition of FAS is composed of reversible fast-binding inhibition, IC50 = 0.7 microg/ml, and irreversible slow-binding inhibition following saturation kinetics with a dissociation constant of 0.68 microg/ml and a limiting rate constant of 0.0288 min(-1). The Extr exhibited different type of inhibitions against the three substrates in the FAS overall reaction. Compared with EGCG in inhibition constant and IC50 value, the Extr appeared to be a more efficient inhibitor, and exhibited a considerable inhibition against the growth of four kinds of cancer cells (patent application number 200510068054.2). It was infered that the inhibitory activity is likely attributable to the co-operative effect of the components.     

Induction of cancer cell apoptosis by flavonoids is associated with their ability to inhibit fatty acid synthase activity

The consumption of food products containing high amounts of flavonoids has been reported to lower the risk of various cancers. The mechanisms underlying the cancer-protective effects of these naturally occurring polyphenolic compounds, however, remain elusive. Based on our previous finding that the cytotoxic effect of the flavanol epigallocatechin-3-gallate on prostate cancer cells correlates with its ability to inhibit fatty acid synthase (FAS, a key lipogenic enzyme overexpressed in many human cancers), we examined the anti-lipogenic effects of a panel of 18 naturally occurring polyphenolic compounds. In addition to epigallocatechin-3-gallate, five other flavonoids, more particularly luteolin, quercetin, kaempferol, apigenin, and taxifolin, also markedly inhibited cancer cell lipogenesis. Interestingly, in both prostate and breast cancer cells, a remarkable dose-response parallelism was observed between flavonoid-induced inhibition of fatty acid synthesis, inhibition of cell growth, and induction of apoptosis. In support for a role of fatty acid synthesis in these effects, the addition of exogenous palmitate, the end product of FAS, markedly suppressed the cytotoxic effects of flavonoids. Taken together, these findings indicate that the potential of flavonoids to induce apoptosis in cancer cells is strongly associated with their FAS inhibitory properties, thereby providing a new mechanism by which polyphenolic compounds may exert their cancer-preventive and antineoplastic effects.     

Elastase release by stimulated neutrophils inhibited by flavonoids: importance of the catechol group

Pathogenesis of chronic inflammatory diseases is associated with excessive elastase release through neutrophil degranulation. In the present study, inhibition of human neutrophil degranulation by four flavonoids (myricetin, quercetin, kaempferol, galangin) was evaluated by using released elastase as a biomarker. Inhibitory potency was observed in the following order: quercetin > myricetin > kaempferol = galangin. Quercetin, the most potent inhibitor of elastase release also had a weak inhibitory effect on the enzyme catalytic activity. Furthermore, the observed effects were highly dependent on the presence of a catechol group at the flavonoid B-ring. The results of the present study suggest that quercetin may be a promising therapeutic agent in the treatment of neutrophil-dependent inflammatory diseases.     

The extract of leaves of Acer truncatum Bunge: A natural inhibitor of fatty acid synthase with antitumor activity

Fatty acid synthase (FAS) has been identified as a potential antitumor target. The extract from the leaves of Acer truncatum Bunge (Extr) was prepared to assay its inhibitory activity against FAS, which was isolated from duck liver, and the correlated antitumor bioactivity. Its inhibition of FAS is composed of reversible fast-binding inhibition, IC₅₀ = 0.7 μg/ml, and irreversible slow-binding inhibition following saturation kinetics with a dissociation constant of 0.68 μg/ml and a limiting rate constant of 0.0288 min^{? 1}. The Extr exhibited different type of inhibitions against the three substrates in the FAS overall reaction. Compared with EGCG in inhibition constant and IC₅₀ value, the Extr appeared to be a more efficient inhibitor, and exhibited a considerable inhibition against the growth of four kinds of cancer cells (patent application number 200510068054.2). It was infered that the inhibitory activity is likely attributable to the co-operative effect of the components.     

Evaluation of the inhibitory activities of aceraceous plants on fatty acid synthase

Fatty acid synthase (FAS) is a very significant lipogenic enzyme participating in energy metabolism in vivo and has been reported as a potential new therapeutic target for cancer treatment. The extracts from sixteen Aceraceae were prepared to assay their inhibitory activities against duck liver FAS and their correlated antitumor bioactivity. Their inhibition of FAS was composed of a reversible fast-binding inhibition, by which 0.41 μg/mL of the A. campestre extract inhibits 50% FAS activity, and an irreversible slow-binding inhibition with inactivation rate constants, k_obs, ranging between 1.5 × 10^{? 3} and 10.6 × 10^{? 3} min^{? 1}. Three Aceraceae extracts were selected from their smaller IC₅₀ values to study different type of inhibitions against the three substrates in the FAS overall reaction. As compared with other reported FAS inhibitors including EGCG with regard to inhibition constant and IC₅₀ value, the extracts appeared to be more efficient inhibitors, and exhibited a considerable inhibition against the growth of five types of cancer cells (China patent application number 200610088901.6), which may be related to the inhibition of lipogenesis in these cells.     

Differential effects of flavonoids on bovine kidney low molecular mass protein tyrosine phosphatase

Among the structurally related flavonoids tested on the bovine kidney low molecular weight protein tyrosine phosphatase (LMrPTP) activity, quercetin activated by about 2.6-fold the p-nitrophenyl-phosphate (p-NPP)-directed reaction, in contrast to morin that acted as a competitive inhibitor, with Ki values of 87, 73 and 50 microM for p-NPP, FMN, and tyrosine-phosphate, respectively. Other related flavonoids, such as rutin, kaempferol, catechin, narigin, phloretin and taxifolin did not significantly affect the LMrPTP activity. The positions of the hydroxyl groups in the structures of the flavonoids were important for their distinct effects on LMrPTP activity. The hydroxyl groups at C3' and C4' and the presence of a double bond at C2 and C3 were essential for the activating effect of quercetin. The absence of the 3'-OH (kaempferol), absence of the double bond (taxifolin) and the presence of the sugar rutinose at the 3-OH (rutin) suppressed the effect of quercetin. The C2'- and C4'-hydroxyl groups, the presence of the double bond, and a C4-ketone group were important requirements for the inhibitory effects of morin.     

Suppression of fatty acid synthase, differentiation and lipid accumulation in adipocytes by curcumin

Curcumin is a well-known component of the cook seasoning and traditional herb turmeric (Curcuma longa), which has been reported to prevent obesity. However, the mechanism still remains to be determined. In this study, curcumin is found to be an effective inhibitor of fatty acid synthase (FAS), and its effects on adipocytes are further evaluated. Curcumin shows both fast-binding and slow-binding inhibitions to FAS. Curcumin inhibits FAS with an IC?? value of 26.8 μM, noncompetitively with respect to NADPH, and partially competitively against both substrates acetyl-CoA and malonyl-CoA. This suggests that the malonyl/acetyl transferase domain of FAS possibly is the main target of curcumin. The time-dependent inactivation shows that curcumin inactivates FAS with two-step irreversible inhibition, a specific reversible binding followed by an irreversible modification by curcumin. Like other classic FAS inhibitors, curcumin prevents the differentiation of 3T3-L1 cells, and thus represses lipid accumulation. In the meantime, curcumin decreases the expression of FAS, down-regulates the mRNA level of PPARγ and CD36 during adipocyte differentiation. Curcumin is reported here as a novel FAS inhibitor, and it suppresses adipocyte differentiation and lipid accumulation, which is associated with its inhibition of FAS. Hence, curcumin is considered to be having potential application in the prevention of obesity.     

Screening and Inhibition Mechanism of Xanthine Oxidase Inhibitors in Ethanolic Extracts of Chimonanthus salicifolius Hu Leaves

This study aimed to evaluate the inhibition of the ethanol elutions of Chimonanthus salicifolius Hu leaves (CsHL) against xanthine oxidase (XO). The results of XO inhibition assay and enzymatic superoxide free radical scavenging assay in vitro showed that 70 % ethanol eluate (EE) had the best inhibitory effect and followed by 40 % EE. High performance liquid chromatograph analysis showed that quercetin and kaempferol were the potential active components of XO inhibition. The inhibition mechanism of quercetin and kaempferol on XO was investigated by kinetic analysis and fluorescence quenching titration assay. The molecular simulation further revealed that quercetin and kaempferol bind to XO mainly by hydrogen bonding and van der Waals, blocking the entry of substrates and leading to the inhibition of XO. In conclusion, the CsHL have inhibitory effects on XO activity, which provides a theoretical basis for relieving or preventing hyperuricemia and gout as a natural food or medicinal plant in the future.     

Differential effects of flavonoids on bovine kidney low molecular mass protein tyrosine phosphatase

Among the structurally related flavonoids tested on the bovine kidney low molecular weight protein tyrosine phosphatase (LMrPTP) activity, quercetin activated by about 2.6-fold the p-nitrophenyl-phosphate (p-NPP)-directed reaction, in contrast to morin that acted as a competitive inhibitor, with Ki values of 87, 73 and 50 μM for p-NPP, FMN, and tyrosine-phosphate, respectively. Other related flavonoids, such as rutin, kaempferol, catechin, narigin, phloretin and taxifolin did not significantly affect the LMrPTP activity.

The positions of the hydroxyl groups in the structures of the flavonoids were important for their distinct effects on LMrPTP activity. The hydroxyl groups at C3′ and C4′ and the presence of a double bond at C2 and C3 were essential for the activating effect of quercetin. The absence of the 3′-OH (kaempferol), absence of the double bond (taxifolin) and the presence of the sugar rutinose at the 3-OH (rutin) suppressed the effect of quercetin. The C2′- and C4′-hydroxyl groups, the presence of the double bond, and a C4-ketone group were important requirements for the inhibitory effects of morin.     

Antifungal effects of the flavonoids kaempferol and quercetin: a possible alternative for the control of fungal biofilms

This study aimed to determine the minimum inhibitory concentration (MIC) of kaempferol and quercetin against planktonic and biofilm forms of the Candida parapsilosis complex. Initially, nine C. parapsilosis sensu stricto, nine C. orthopsilosis and nine C. metapsilosis strains were used. Planktonic susceptibility to kaempferol and quercetin was assessed. Growing and mature biofilms were then exposed to the flavonoids at MIC or 10xMIC, respectively, and theywere also analyzed by confocal laser scanning microscopy. The MIC ranges were 32-128 µg ml^?1 for kaempferol and 0.5-16 µg ml^?1 for quercetin. Kaempferol and quercetin decreased (P?<?0.05) the metabolic activity and biomass of growing biofilms of the C. parapsilosis complex. As for mature biofilms, the metabolic effects of the flavonoids varied, according to the cryptic species, but kaempferol caused an overall reduction in biofilm biomass. Microscopic analyses showed restructuring of biofilms after flavonoid exposure. These results highlight the potential use of these compounds as sustainable resources for the control of fungal biofilms.     

Acylated flavonol tri- and tetraglycosides in the flavonoid metabolome of Cladrastis kentukea (Leguminosae)

The foliar metabolome of Cladrastis kentukea (Leguminosae) contains a complex mixture of flavonoids including acylated derivatives of the 3-O-rhamnosyl(1→2)[rhamnosyl(1→6)]-galactosides of kaempferol and quercetin and their 7-O-rhamnosides, together with an array of non-acylated kaempferol and quercetin di-, tri- and tetraglycosides. Thirteen of the acylated flavonoids, 12 of which had not been reported previously, were characterised by spectroscopic and chemical methods. Eight of these were the four isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-β-d-galactopyranoside) and their 7-O-α-l-rhamnopyranosides, and three were isomers of quercetin 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-β-d-galactopyranoside) - the remaining 4Z isomer was identified by LC-UV-MS analysis of a crude extract. The final two acylated flavonoids characterised by NMR were the 3E and 4E isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E-feruloyl-β-d-galactopyranoside)-7-O-α-l-rhamnopyranoside while the 3Z and 4Z isomers were again detected by LC-UV-MS. Using the observed fragmentation behaviour of the isolated compounds following a variety of MS experiments, a further 18 acylated flavonoids were given tentative structures by LC-MS analysis of a crude extract. Acylated flavonoids were absent from the flowers of C. kentukea, which contained an array of non-acylated kaempferol and quercetin glycosides. Immature fruits contained kaempferol 3-O-α-rhamnopyranosyl(1→2)[α-rhamnopyranosyl(1→6)]-β-galactopyranoside and its 7-O-α-rhamnopyranoside as the major flavonoids with acylated flavonoids, different from those in the leaves, only present as minor constituents. The presence of acylated flavonoids distinguishes the foliar flavonoid metabolome of C. kentukea from that of a closely related legume, Styphnolobium japonicum, which contains a similar range of non-acylated flavonoids.     

Effects of compounds found in Nidus Vespae on the growth and cariogenic virulence factors of Streptococcus mutans

Nidus Vespae (honeycomb) is a kind of traditional Chinese medicine that has been demonstrated to inhibit the growth and acid-production of oral cariogenic bacteria. Subsequent studies showed that the chloroform/methanol (Chl/MeOH) chemical extraction of Nidus Vespae was the most effective inhibitor of growth and acidogenicity of Streptococcus mutans. In this study, we isolated the chemical compounds of the Nidus Vespae Chl/MeOH extraction, tested their antimicrobial activity against six cariogenic bacteria and further evaluated the acid inhibition properties, anti-F-ATPase activity and anti-LDH activity against S. mutans. The isolated flavonoids, quercetin and kaempferol, inhibited the growth of bacteria (S. mutans, Streptococcus sobrinus, Streptococcus sanguis, Actinomyces viscosus, Actinomyces naeslundii and Lactobacillus rhamnosus) with minimum inhibitory concentrations (MICs) ranging from 1 to 4 mg/ml and minimum bactericidal concentrations (MBCs) from 4 to 16 mg/ml. In addition, quercetin and kaempferol at sub-MIC levels significantly inhibited acidogenicity and acidurity of S. mutans cells. Treated with the test agents, the F-ATPase activity was reduced by 47.37% with 1mg/ml quercetin and by 49.66% with 0.5mg/ml kaempferol. The results showed that quercetin and kaempferol contained in Chl/MeOH extraction presented remarkably biological activity, suggesting that Nidus Vespae might be useful as a potential preventive and therapeutic agent in dental caries.     

Mechanism of oxidative DNA damage induced by quercetin in the presence of Cu(II)

Quercetin, one of flavonoids, has been reported to be carcinogenic. There have been no report concerning carcinogenicity of kaempferol and luteolin which have structure similar to quercetin. DNA damage was examined by using DNA fragments obtained from the human p53 tumor suppressor gene. Quercetin induced extensive DNA damage via reacting with Cu(II), but kaempferol and luteolin induced little DNA damage even in the presence of Cu(II). Excessive quercetin inhibited copper-dependent DNA damage induced by quercetin. Bathocuproine, a Cu(I)-specific chelator, catalase and methional inhibited the DNA damage by quercetin, whereas free hydroxyl radical scavengers did not. Site specificity of the DNA damage was thymine and cytosine residues. The site specificity and the inhibitory effects suggested that DNA-copper-oxygen complex rather than free hydroxyl radical induced the DNA damage. Formation of 8-oxodG by quercetin increased extensively in the presence of Cu(II), whereas 8-oxodG formation by kaempferol or luteolin increased only slightly. This study suggests a good relationship between carcinogenicity and oxidative DNA damage of three flavonoids. The mechanism of DNA damage by quercetin was discussed in relation to the safety in cancer chemoprevention by flavonoids.     

Structure-activity relationship of polyphenols that inhibit fatty acid synthase

Many flavone derivatives inhibit FAS, and their A and B rings play an important role, but is the C ring necessary for the inhibition of FAS? Here, using nordihydroguaiaretic acid (NDGA), with two phenyl rings connected by a four-carbon chain, as a representative, the structural basis for the inhibition of animal fatty acid synthase (FAS) by polyphenols was investigated. NDGA potently inhibits the overall reaction of FAS (IC(50) = 9.3 +/- 0.1 muM). The kinetic study indicated that NDGA inhibits FAS competitively with respect to acetyl-CoA, noncompetitively with respect to malonyl-CoA, and in a mixed manner with respect to NADPH. The inhibitory mechanism is the same as that of FAS flavonoid inhibitors. This suggests that the C ring of flavonoids is not essential for their FAS inhibitory effect. This conclusion was further confirmed by the results obtained for different polyphenols. A structure-activity relationship study indicated that a biphenyl core exists in all FAS polyphenol inhibitors. Thus, we propose a common model possibly shared by all FAS polyphenol inhibitors. The model includes two almost planar aromatic rings with their respective hydroxyl groups, and a proper ester linkage between the two rings that possibly causes the inhibition of FAS by irreversibly inhibiting the beta-ketoacyl reductase domain.     

Constituents in Easter lily flowers with medicinal activity

Easter lily (Lilium longiflorum) flowers have been used in traditional medicine for alleviating many ailments. However, the chemical basis of its bioactivity has not been investigated. We have determined bioactive components in Easter lily flowers using lipid peroxidation and cyclooxygenase enzyme inhibitory assays and found to be kaempferol (1), kaempferol glycosides (2, 3, 4, 8, 9 and 10), quercetin glycosides (5, 6 and 7), a regaloside (11), a chalcone (12) and a fatty acid fraction (13). The structures of compounds were determined by NMR, IR, UV/VIS and mass spectroscopic studies. Compound 1 showed the highest COX-1 inhibition (94.1%) followed by 3, 8 and 12 with 38.7, 30.8 and 32.4%, respectively. Only compound 1 inhibited COX-2 enzyme by 36.9% at 80 ppm. In lipid peroxidation inhibitory assay, kaempferol showed 37 and 100 % inhibitions at 1 and 10 ppm, respectively. At 10 ppm, more than 20% inhibition was observed for compounds 4, 7, 10, 11 and 12 and 53% for compound 3. The compounds reported in here are isolated for the first time from Easter lily flowers including novel compounds 10, 11 and 12. Our results suggest that kaempferol and quercetin flavonoids contributed to the anecdotal medicinal properties of Easter lily flowers.     

Inhibition of Xanthine Oxidase by Flavonoids

The influence of nineteen flavonoids on cow’s milk xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.2.3.2) was investigated. The enzyme activity was estimated by measuring the increase in absorbance at 290 nm due to uricate formation as well as by a colorimetric method assaying hydrogen peroxide generated from uricate by uricase. Among the flavonoids tested, myricetin, kaempferol, quercetin, fisetin, quercitrin, and morin inhibited the enzyme strongly at 50 μm; the concentrations which gave 50% inhibition (ID₅₀) were 2, 2, 3, 7, 15, and 19μm, respectively. The inhibition mode of the former three compounds was of mixed type and the kinetic parameters were determined. Chrysin and naringenin were moderately inhibitory, while other flavonoids showed weak to no inhibition.     

Flavonoids, but not protein kinase C inhibitors, prevent stress protein synthesis during erythrophagocytosis.

Erythrophagocytosis induces in monocytes-macrophages the synthesis of stress proteins including the classical heat shock proteins (HSPs) and heme oxygenase (HO). To evaluate the role of oxygen radicals in this induction, we used the antioxidant flavonoids quercetin and kaempferol. These compounds inhibited HSP and HO synthesis, the latter being more sensitive. Quercetin and kaempferol also are inhibitors of protein kinase C (PKC). In order to determine whether inhibition of stress protein synthesis by flavonoids was mediated by their antioxidant properties or by PKC inhibition, we also tested more specific PKC antagonists, staurosporine and H-7. Staurosporine (SS) and H-7 decreased the synthesis of HSP70 and HSP83 but had no effect on HO. These data suggest that (1) erythrophagocytosis-related oxygen radicals are involved in the induction of the stress response in phagocytic cells, (2) the induction of HSPs and HO is differentially regulated, and (3) the effects of flavonoids on HO are linked to their scavenging activity rather than to PKC modulation.