Essential Oil of Thymus munbyanus subsp. coloratus from Algeria: Chemotypification and in vitro Biological Activities.

Thymus munbyanus subsp. coloratus (Lamiaceae) is a small shrub endemic to Algeria and Morocco where is found in lawns, rockeries and mountainous regions. From a phytochemical point of view this taxon has never been characterized. In this work we have analysed the chemical compositions of the essential oils obtained from inflorescences and vegetative parts by GC/MS. A new chemotype, i.e. borneol-chemotype, was characterized for the first time in the species. Furthermore, we assessed the biological activities of essential oils, namely the antioxidant, antimicrobial and cytotoxicity on tumor cells that were evaluated by the DPPH, ABTS, and FRAP, disc diffusion, and MTT methods, respectively. Biological assays highlighted a moderate inhibitory effect on Staphylococcus aureus, Escherichia coli and Candida albicans (inhibition zone diameter in the range 9 - 10 mm), and noteworthy cytotoxicity on A375 human melanoma cells (IC50 of 46.95 µg/ml).

Bioactive Secondary Metabolites from Schizogyne sericea (Asteraceae) Endemic to Canary Islands.

Schizogyne sericea (Asteraceae) is a halophytic shrub endemic to the Canary Islands and traditionally employed as analgesic, astringent, anti-inflammatory, and vulnerary. A comprehensive phytochemical investigation was conducted on the flowering aerial parts by analyzing both essential oil constituents and polar compounds. The essential oil was dominated by p-cymene, with the noteworthy occurrence of ß-pinene and thymol esters. From the EtOH extract, eight compounds were isolated and structurally elucidated. Essential oil, polar fractions, and isolates (2), (4), and (5) were separately in vitro assayed for antiproliferative activity on human tumor cell lines (A375, MDA-MB 231, and HCT116) by MTT assay, for antioxidant potential by DPPH, ABTS, and FRAP assays, and for antimicrobial activity by the agar disk diffusion method. Results revealed that essential oil and compounds 1 and 2 exert a strong inhibition on tumor cells, and in some cases, higher than that of cisplatin. Fractions containing thymol derivatives (1 and 2) and caffeoylquinic acid derivatives 4 and 5 displayed antioxidant activity comparable to that of Trolox, making S. sericea extract an interesting natural product with potential applications as preservative or in the treatment of diseases in which oxidative stress plays an important role.

Biological Activities of the Essential Oil from Erigeron floribundus.

Erigeron floribundus (Asteraceae) is an herbaceous plant widely used in Cameroonian traditional medicine to treat various diseases of microbial and non-microbial origin. In the present study, we evaluated the in vitro biological activities displayed by the essential oil obtained from the aerial parts of E. floribundus, namely the antioxidant, antimicrobial and antiproliferative activities. Moreover, we investigated the inhibitory effects of E. floribundus essential oil on nicotinate mononucleotide adenylyltransferase (NadD), a promising new target for developing novel antibiotics, and Trypanosoma brucei, the protozoan parasite responsible for Human African trypanosomiasis. The essential oil composition was dominated by spathulenol (12.2%), caryophyllene oxide (12.4%) and limonene (8.8%). The E. floribundus oil showed a good activity against Staphylococcus aureus (inhibition zone diameter, IZD of 14 mm, minimum inhibitory concentration, MIC of 512 µg/mL). Interestingly, it inhibited the NadD enzyme from S. aureus (IC50 of 98 µg/mL), with no effects on mammalian orthologue enzymes. In addition, T. brucei proliferation was inhibited with IC50 values of 33.5 µg/mL with the essential oil and 5.6 µg/mL with the active component limonene. The essential oil exhibited strong cytotoxicity on HCT 116 colon carcinoma cells with an IC50 value of 14.89 µg/mL, and remarkable ferric reducing antioxidant power (tocopherol-equivalent antioxidant capacity, TEAC = 411.9 µmol·TE/g).

Syntheses, structures, and antimicrobial activity of new remarkably light-stable and water-soluble tris(pyrazolyl)methanesulfonate silver(I) derivatives of N-methyl-1,3,5-triaza-7-phosphaadamantane salt - [mPTA]BF4.

Two new silver(I) complexes of formula [Ag(mPTA)4](Tpms)4(BF4) (1) and [Ag(Tpms)(mPTA)](BF4) (2) (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane cation, Tpms = tris(pyrazol-1-yl)methanesulfonate anion) have been synthesized and fully characterized by elemental analyses, (1)H and (31)P{(1)H} NMR, ESI-MS, and IR spectroscopic techniques. The single-crystal X-ray diffraction study of 1 discloses a noncoordinated nature of the Tpms species, existing as counterions around the highly charged metal center [Ag(mPTA)](5+), 1 being the first reported coordination compound bearing a κ(0)-Tpms. 1 features high solubility and stability in water (S25 °C ≈ 30 mg·mL(-1)). The two complexes interact with calf thymus DNA via intercalation mode, binding to the BSA with decrease of its tryptophan fluorescence with a static quenching mechanism. The two new silver complexes exhibit significant antibacterial and antifungal activities screened in vitro against the standard strains of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans.

In vitro biological activities of seed essential oils from the Cameroonian spices Afrostyrax lepidophyllus MILDBR. and Scorodophloeus zenkeri HARMS rich in sulfur-containing compounds.

The chemical composition of the essential oils obtained from the seeds of bush onion (Afrostyrax lepidophyllus) and tropical garlic tree (Scorodophloeus zenkeri), plants used as spices in the traditional African cuisine, was determined by GC-FID and GC/MS analyses. Moreover, in vitro biological properties of the oils, namely, the cytotoxic, antioxidant, and antimicrobial activities, were investigated by the MTT, the DPPH(.) and ABTS(.+) scavenging, and the agar disc-diffusion methods, respectively. Both oils were composed mainly by S-containing compounds, accounting for 91.0-96.1% of the total oil compositions, which provided them the typical garlic- and onion-like odors of spices. The predominant compound in both oils, 2,4,5,7-tetrathiaoctane (1; 51.5-52.9%), was isolated by preparative TLC and structurally elucidated by (1) H- and (13) C-NMR data. The oils exhibited a strong inhibitory effect on the growth of human cancer cells, namely, T98G (human glioblastoma multiforme cell line), MDA-MB 231 (human breast adenocarcinoma cell line), A375 (human malignant melanoma cell line), and HCT116 (human colon carcinoma cell line) cells, and a good DPPH(.) - and ABTS(.+) -scavenging activity, while the antimicrobial effects were negligible. The volatile compositions of A. lepidophyllus and S. zenkeri oils supported their use as odorous spices. The significant inhibition activities detected make these oils worthy of further investigation as promising chemopreventive agents to be exploited in the African pharmaceutical market.

Chemical composition and biological activities of the essential oil of Athanasia brownii Hochr. (Asteraceae) endemic to Madagascar.

The essential oil obtained from hydrodistillation of flowering aerial parts of Athanasia brownii (Asteraceae) was studied for its chemical composition by GC/FID and GC/MS, and for biological activity, namely, antioxidant, antimicrobial, and chemopreventive potential, by DPPH (=2,2-diphenyl-1-picrylhydrazyl), ABTS (=2,2'-azinobis[3-ethylbenzothioline-6-sulfonic acid), and FRAP (=ferric reducing antioxidant power), disk diffusion test, and MTT (=3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, respectively. The oil was characterized by a high content of oxygenated sesquiterpenes (71.2%), with selin-11-en-4α-ol (24.6%), caryophyllene oxide (8.7%), humulene epoxide II (5.1%), and (E)-nerolidol (4.9%) as the predominant compounds. The oil showed a moderate activity against streptococci as well as radical-scavenging potential, while the inhibitory effects against human cancer cells examined such as A375 (malignant melanoma) and HCT 116 (colon carcinoma) were significant, with IC50 values of 19.85 and 29.53 µg/ml, respectively.

Chemical composition and in vitro biological activities of the essential oil of Vepris macrophylla (BAKER) I.VERD. endemic to Madagascar.

Vepris macrophylla is an evergreen tree occurring in sub-humid forest of Madagascar and traditionally used in the Island to treat several complaints as well as to prepare aromatic teas and alcoholic drinks. In the present work, the essential oil distilled from the leaves was analyzed for the first time by gas chromatography (GC-FID) and gas chromatography/mass spectrometry (GC/MS). The major compounds were citral (56.3%), i.e., mixture of neral (23.1%) and geranial (33.2%), citronellol (14.5%), and myrcene (8.3%). The essential oil exhibited antimicrobial activity against S. aureus, P. aeruginosa, and C. albicans as determined by vapor-diffusion assay, supporting the traditional use of the plant for preparing steam bath for the treatment of infectious diseases. The essential oil was evaluated for cytotoxic activity on human tumor cell lines by MTT (=3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay, showing inhibitory effects comparable to those of cisplatin, notably on MDA-MB 231 (human breast adenocarcinoma) and HCT116 (human colon carcinoma) cell lines. Finally, the essential oil was also subjected to screening for its antioxidant activity and the free radical scavenging capacity.

Synthesis, antimicrobial and antiproliferative activity of novel silver(I) tris(pyrazolyl)methanesulfonate and 1,3,5-triaza-7-phosphadamantane complexes.

Five new silver(I) complexes of formulas [Ag(Tpms)] (1), [Ag(Tpms)(PPh(3))] (2), [Ag(Tpms)(PCy(3))] (3), [Ag(PTA)][BF(4)] (4), and [Ag(Tpms)(PTA)] (5) {Tpms = tris(pyrazol-1-yl)methanesulfonate, PPh(3) = triphenylphosphane, PCy(3) = tricyclohexylphosphane, PTA = 1,3,5-triaza-7-phosphaadamantane} have been synthesized and fully characterized by elemental analyses, (1)H, (13)C, and (31)P NMR, electrospray ionization mass spectrometry (ESI-MS), and IR spectroscopic techniques. The single crystal X-ray diffraction study of 3 shows the Tpms ligand acting in the N(3)-facially coordinating mode, while in 2 and 5 a N(2)O-coordination is found, with the SO(3) group bonded to silver and a pendant free pyrazolyl ring. Features of the tilting in the coordinated pyrazolyl rings in these cases suggest that this inequivalence is related with the cone angles of the phosphanes. A detailed study of antimycobacterial and antiproliferative properties of all compounds has been carried out. They were screened for their in vitro antimicrobial activities against the standard strains Enterococcus faecalis (ATCC 29922), Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (ATCC 49619), Streptococcus pyogenes (SF37), Streptococcus sanguinis (SK36), Streptococcus mutans (UA159), Escherichia coli (ATCC 25922), and the fungus Candida albicans (ATCC 24443). Complexes 1-5 have been found to display effective antimicrobial activity against the series of bacteria and fungi, and some of them are potential candidates for antiseptic or disinfectant drugs. Interaction of Ag complexes with deoxyribonucleic acid (DNA) has been studied by fluorescence spectroscopic techniques, using ethidium bromide (EB) as a fluorescence probe of DNA. The decrease in the fluorescence of DNA-EB system on addition of Ag complexes shows that the fluorescence quenching of DNA-EB complex occurs and compound 3 is particularly active. Complexes 1-5 exhibit pronounced antiproliferative activity against human malignant melanoma (A375) with an activity often higher than that of AgNO(3), which has been used as a control, following the same order of activity inhibition on DNA, i.e., 3 > 2 > 1 > 5 > AgNO(3)≫ 4.

Draft genome of an extremely drug-resistant st551 Staphylococcus pseudintermedius from an Italian dog with otitis externa.

OBJECTIVES: To determine the draft genome sequence and analyse the genetic features of a Staphylococcus pseudintermedius clinical isolate according to the main typing schemes available, with a special focus on antibiotic resistance. METHODS: The strain was isolated from a case of otitis externa in a dog. Its identity and pattern of antibiotic susceptibility were determined using an automated system. The genome was sequenced using an Illumina platform. MLST, SCCmec typing, resistome, and mobile genetic elements were derived by comparative analysis using available specific databases. RESULTS: S. pseudintermedius CAM1 isolate has a chromosome size of 2 652 610 bp. It showed a wide pattern of phenotypic resistance, comprising beta-lactams, macrolides and lincosamides, aminoglycosides, fluoroquinolones, tetracyclines, and trimethoprim-sulfamethoxazole. The genetic determinants of the underlying mechanisms were all found by in silico analysis of the genome. The mecA gene for methicillin resistance was harboured by the Vc type of the SCCmec. MLST of the strain was st551. CONCLUSION: By comparison with the MLST database of S. pseudintermedius and data from published molecular epidemiology studies, CAM1 is the first st551 strain recorded in Italy and, in the context of an already extremely wide antibiotic resistance pattern, it harbours also the tetK gene, the prevalence of which is rare in MDR S. pseudintermedius.

Lysogenic transfer of mef(A) and tet(O) genes carried by Phim46.1 among group A streptococci.

We report the ex vivo lysogenic transfer of erythromycin and tetracycline resistance genes among group A streptococci (GAS). Of 42 susceptible strains, 69% acquired erythromycin/tetracycline resistance when infected with purified supernatants from strain m46 culture containing the phage Φm46.1. A significant emm-type-dependent barrier to lysogenic transfer was not observed. The emm12 strains were the only strains susceptible to the lytic action of the bacteriophage preparation.

Coffee silverskin extracts: Quantification of 30 bioactive compounds by a new HPLC-MS/MS method and evaluation of their antioxidant and antibacterial activities.

The research of value-added applications for coffee silverskin (CSS) requires studies to investigate potential bioactive compounds and biological activities in CSS extracts. In this study, different ultrasound-assisted extraction (UAE) methods have been tested to extract bioactive compounds from CSS. The obtained extracts, were characterized using a new HPLC-MS/MS method to detect and quantify 30 bioactive compounds of 2 classes: alkaloids and polyphenols (including phenolic acids, flavonoids, and secoiridoids). CSS extracts obtained with ethanol/water (70:30) as extraction solvent showed the highest levels (p ≤ 0.05) of bioactive compounds (4.01 ± 0.34% w/w). High content of caffeine was observed with levels varying from 1.00% to 3.59% of dry weight of extract (dw). 18 phenolic compounds were detected in CSS extracts with caffeoylquinic acids (3-CQA, 5-CQA and 3,5-diCQA) as the most abundant polyphenols (3115.6 µg g to -5444.0 µg g-1). This study is also one of the first to characterize in-depth flavonoids in CSS revealing the levels of different flavonoids compounds such as rutin (1.63-8.70 µg g-1), quercetin (1.53-2.46 µg g-1), kaempferol (0.76-1.66 µg g-1) and quercitrin (0.15-0.51 µg g-1). Neuroprotective activity of silverskin extracts against H2O2-induced damage was evaluated for the first time suggesting for methanol and ethanol/water (70:30) extracts a potential role as protective agents against neurodegeneration due to their ability to counteract oxidative stress and maintain cell viability. Silverskin extracts were not inhibiting the growth of anyone of the bacterial species included in this study but data obtained by water extract might deserve a deeper future investigation on biofilm-related activities, such as quorum sensing or virulence factors' expression. From their composition and their evidenced biological activities, CSS extracts could represent valuable ingredients in nutraceutical formulations.

The volatile oils from the oleo-gum-resins of Ferula assa-foetida and Ferula gummosa: A comprehensive investigation of their insecticidal activity and eco-toxicological effects.

Since time immemorial, the oleo-gum-resins of Ferula assa-foetida and F. gummosa are used in the traditional medical systems as well as in foodstuffs, perfumery and cosmetics. In the present study, we explored the insecticidal efficacy of the essential oils obtained from these oleo-gum-resins to widen their fields of industrial applications. The two essential oils were mainly composed of sulfides [sec-butyl (Z)-propenyl disulfide, sec-butyl (E)-propenyl disulfide, sec-butyl (Z)-propenyl trisulfide and sec-butyl (E)-propenyl trisulfide)] and monoterpenes (α-pinene, ß-pinene and ß-phellandrene), respectively, as determined by GC-MS analysis. The two essential oils were assayed for toxicity on a panel of insects, represented by species of public health relevance (Culex quinquefasciatus and Musca domestica), agricultural (Spodoptera littoralis) and stored-product pests (Prostephanus truncatus and Trogoderma granarium). The ecotoxicological effects of the essential oils were assessed on the aquatic microcrustacean Daphnia magna and the earthworm Eisenia fetida, as well as on human cells. Overall, the two essential oils were effective against important insect pests and vectors. On the other hand, they resulted cytotoxic to fibroblasts and non-target aquatic microcrustaceans. Thus, further insights are needed to determine the full spectrum of their eco-toxicological effects.

Exploring new applications of tulip tree (Liriodendron tulipifera L.): leaf essential oil as apoptotic agent for human glioblastoma.

Liriodendron tulipifera L. (Magnoliaceae), also known as "tulip tree," is a hardwood plant native to North America, cultivated all over the world and used on an industrial level, especially for its fine wood and to make honey. It has also been traditionally exploited for its antimalarial properties. However, our knowledge about the bioactivity of its essential oil remains patchy. In this research, we focused on the biological evaluation of the volatile fractions obtained from different parts of the plant which are normally discharged by industry, including leaves, flowers, and fruits. For the purpose, the essential oils were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). Then, they were evaluated as radical scavenging, antioxidant, antimicrobial, and antiproliferative agents by using DPPH, ABTS, FRAP, disk diffusion, and MTT methods, respectively. The significant toxicity exhibited on human tumor cells, namely A375 malignant melanoma, HCT116 colon carcinoma, MDA-MB 231 breast adenocarcinoma, and T98G glioblastoma multiforme cell lines, prompted us to study the mechanism of action by acridine orange/ethidium bromide double staining and caspase 3 assays. Our findings shed light on the potential applications of tulip tree derivatives as anticancer drugs.

Antidiabetic "gliptins" affect biofilm formation by Streptococcus mutans.

Streptococcus mutans, a dental caries causing odontopathogen, produces X-prolyl dipeptidyl peptidase (Sm-XPDAP, encoded by pepX), a serine protease known to have a nutritional role. Considering the potential of proteases as therapeutic targets in pathogens, this study was primarily aimed at investigating the role of Sm-XPDAP in contributing to virulence-related traits. Dipeptidyl peptidase (DPP IV), an XPDAP analogous enzyme found in mammalian tissues,is a well known therapeutic target in Type II diabetes. Based on the hypothesis that gliptins, commonly used as anti-human-DPP IV drugs, may affect bacterial growth upon inhibition of Sm-XPDAP, we have determined their ex vivo antimicrobial and anti-biofilm activity towards S. mutans. All three DPP IV drugs tested reduced biofilm formation as determined by crystal violet staining. To link the observed biofilm inhibition to the human-DPP IV analogue present in S. mutans UA159, a pepX isogenic mutant was generated. In addition to reduced biofilm formation, CLSM studies of the biofilm formed by the pepX isogenic mutant showed these were comparable to those formed in the presence of saxagliptin, suggesting a probable role of this enzyme in biofilm formation by S. mutans UA159. The effects of both pepX deletion and DPP IV drugs on the proteome were studied using LC-MS/MS. Overall, this study highlights the potential of Sm-XPDAP as a novel anti-biofilm target and suggests a template molecule to synthesize lead compounds effective against this enzyme.

High prevalence of clonally diverse spa type t026 Staphylococcus aureus contaminating rural eggshells.

PURPOSE: The presence of Staphylococcus aureus in poultry and poultry products, including eggs, increases its potential to enter the food chain, resulting in foodborne diseases. In this context, eggshell colonization by staphylococci may represent a risk factor. This study aimed to investigate the contamination of rural eggshell by S. aureus and to characterize the key features of the isolated strains. METHODOLOGY: Antibiotic resistance was assessed by disc diffusion. Resistant isolates were analysed by PCR for the identification of associated genetic determinants of resistance. PCR was also used to screen for the presence of genes coding for toxins, namely, sea, sec, sei, sem, seo and tst. The genetic characterization was extended by means of agr locus typing and spa typing. RESULTS: 34 S. aureus were isolated. Macrolide- and tetracycline-resistant strains were prevalent. All strains were susceptible to oxacillin, cefoxitin and trimethoprim-sulfamethoxazole. PCR screening for genes encoding enterotoxins detected several virulence patterns, which, together with spa-typing and agr-locus typing, allowed cluster analysis and the description of novel clones. CONCLUSION: Continuous monitoring of staphylococci is needed also in rural or natural settings. Increasing the number of samples and expanding the geographical region will be needed to further extend the significance of the study.

Antioxidant and antibiofilm activities of secondary metabolites from Ziziphus jujuba leaves used for infusion preparation.

Ziziphus jujuba Mill., jujube, leaf infusions are popular bedtime beverages as they improve sleep by soothing the nerves. With the aim of providing further insights into the polyphenol content of jujube leaf infusion and their antioxidant activities, a 2,2-diphenyl-1-picrylhydrazyl (DPPH)-guided purification of the aqueous extract of Z. jujuba Mill. leaves was conducted. Three major antioxidant polyphenols (i.e. quercitrin, catechin and gallocatechin) of the leaves were identified. In addition, a significant antibiofilm bioactivity against Streptococcus mutans, a causative agent of human dental caries, was detected for the aqueous leaf extract and its bio-guided separation resulted in the identification of the lupane triterpenoid alphitolic acid as the main antibiofilm metabolite. The results herein presented further promote the consumption of jujube leaf infusion as a healthy antioxidant bedtime beverage, and associate it to an unreported anti-caries activity.

Antimicrobial and antioxidant activity of the essential oil from the Carpathian Thymus alternans Klokov.

The genus Thymus includes several species that are used as flavouring, food preservative as well as in cosmetics. Their secondary metabolites have been extensively studied for pharmacological effects. Nonetheless, some species are neglected and deserve to be explored for chemical composition and biological activities. This is the case with Thymus alternans, a Carpathian bush used as a food additive and for the preparation of a traditional herbal medicine. In this work, we have analysed the chemical composition of T. alternans essential oil by GC and GC-MS and evaluated its antimicrobial and antioxidant activity by disc diffusion, DPPH, ABTS and FRAP methods, respectively. Results showed that T. alternans belongs to the nerolidol chemotype, being rich of this sesquiterpene alcohol (15.8%) which might contribute to the antimicrobial (particularly effective on C. albicans growth) and antioxidant (weak inhibition on ABTS radical and reducing power) activities observed.

Rosmarinus eriocalyx: An alternative to Rosmarinus officinalis as a source of antioxidant compounds.

Rosmarinus eriocalyx is an aromatic evergreen bush endemic to Algeria where it is used as a condiment to flavour soups and meat and as a traditional remedy. In the present work we have analyzed for the first time the phenolic composition of polar extracts obtained from stems, leaves and flowers of R. eriocalyx by HPLC, and determined the antioxidant and antimicrobial effects by DPPH, ABTS, FRAP, ORAC and agar disc diffusion methods, respectively. Results showed that ethanolic extracts of leaves and flowers are a rich source of phenolic compounds, mainly rosmarinic acid, carnosic acid and carnosol that are the main responsible for the noteworthy antioxidant activity observed in the assays. This study showed that R. eriocalyx might be a spice to be included in the European food additive list and used as a preservative agent besides R. officinalis.

Phenolic acids, antioxidant and antiproliferative activities of Naviglio® extracts from Schizogyne sericea (Asteraceae).

Schizogyne sericea, well-known as 'salado', is a halophytic shrub widespread on coastal rocks of Tenerife (Canary Islands). This plant is used traditionally as analgesic, astringent, anti-inflammatory and vulnerary agent. In the present work, we have analysed the aqueous and ethanolic extracts of S. sericea for the content of phenolic acids by HPLC-DAD. The dynamic solid-liquid Naviglio® extractor was used to extract the flowering aerial parts. Aqueous extracts showed higher levels of phenolics than ethanolic extracts. S. sericea extracts were rich in chlorogenic and isochlorogenic acids. The Naviglio® extracts obtained were assayed for in vitro biological activities, namely antioxidant, antimicrobial and cytotoxicity on tumour cells by DPPH, ABTS, FRAP, agar disc-diffusion and MTT methods, respectively. Results showed that aqueous extracts, being richer in phenolic acids, are endowed with relevant radical scavenging activity (TEAC values in the range 208-960 µmol TE/g) while ethanolic extracts exhibited noteworthy antiproliferative effects on tumour cells.

Molecular cloning and biochemical characterization of Xaa-Pro dipeptidyl-peptidase from Streptococcus mutans and its inhibition by anti-human DPP IV drugs.

Streptococcus mutans harbours an intracellular, human DPP IV-analogous enzyme Xaa-Pro dipeptidyl-peptidase (EC 3.4.14.11). According to previous reports, an extracellular isozyme in S. gordonii and S. suis has been associated with virulence. Speculating that even an intracellular form may aid in virulence of S. mutans, we have tried to purify, characterize and evaluate enzyme inhibition by specific inhibitors. The native enzyme was partially purified by ion-exchange and gel filtration chromatography. Owing to low yield, the enzyme was overexpressed in Lactococcus lactis and purified by affinity chromatography. The recombinant enzyme (rSm-XPDAP) had a specific activity of 1070 U mg(-1), while the Vmax and Km were 7 µM min(-1) and 89 ± 7 µM (n = 3), respectively. The serine protease inhibitor phenylmethylsulphonyl fluoride and a DPP IV-specific inhibitor diprotin A proved to be active against rSm-XPDAP. As a novel approach, the evaluation of the effect of anti-human DPP IV (AHD) drugs on rSm-XPDAP activity found saxagliptin to be effective to some extent (Ki = 129 ± 16 µM), which may lead to the synthesis and development of a new class of antimicrobial agents.