Cytotoxic compounds from the genus Centaurea.

This thesis, which is divided into four chapters, represents an account on the isolation, identification and the assessment of bioactivity of cytotoxic compounds from the genus Centaurea (Family: Asteraceae alto Compositae), a large genus of about 500 species. The first three chapters deal with an introduction of natural products and Centaurea species, followed by the isolation and characterisation of compounds from twelve Centaurea species. The last chapter describes the bioactivities of extracts and isolated compounds from these species. A total of 45 compounds were isolated from twelve Centaurea species, and only C. americana, C. cyanus, C. dealbata and C. macrocephala had previously been studied. Four of these are novel compounds. Four lignans arctiin, matairesinoside, matairesinol and lappaol A were isolated fromthe methanol extract of C. macrocephala seeds. Arctiin and matairesinoside were also isolated from the methanol extract of C. americana, C. bornmuel/eri, C. dealbata, C. huber-morathii, C. mucronifera, C. pamphylica, C. schischkinii and C. urvillei. The methanol extract of C. americana also afforded 20-hydroxyecdysone, 24-hydroxyecdysone, lappaol A, arctigenin and a novel compound, 3"-O-caffeoyl(9"'->3")-arctiin. The methanol extract of C. cyanus produced lariciresinol 4-0-B-D-glucoside, berchemol, moschamine and cis-moschamine. Arctigenin, astragalin, afzelin, matairesinol and a novel indole alkaloids, schischkiniin, were isolated from the methanol extract of C. schischkinii. Extract from C. bornmuelleri afforded arctigenin, astragalin, afzelin and matairesinol. The methanol extract of C. mon/ana yielded berchemol, berchemol 4'-O-B-D-glucoside, p-coumaroylquinic acid, cis-pcoumaroylquinic acid, pinoresinol, pinoresinol mono methyl ether, pinoresinol dimethyl ether, pinoresinol 4-0-B-D-glucoside, pinoresinol 4,4'di-0-B-D-glucoside, pinoresinol 4-0-apiose-(1->2)-B-D-glucoside, centcyamine, cis-centcyamine, N-(4-hydroxycinnamoyl)-5-hydroxytryptamine, cis-N-(4-hydroxycinnamoyl)-5-hydroxytryptamine, moschamine, cis-moschamine, tryptamine and two novel compounds, flavanone-apiose-glucuronic acid and montamine. C. gigantea afforded arctiopicrin, 8-0-(4-hydroxy-3-methylbutanoyl)-salonitenolide, chlorogenic acid, cirsiliol, isoquercetrin, orientin, isoorientin and 4"-hydroxybenzoyl-isoorientin. General toxicity, cytotoxicity and antioxidant activity of the extracts and isolated compounds were evaluated, respectively, by the brine shrimp lethality assay, MTT assay on human colon cancer cell line (CaCo-2) and DPPH assay. Among all the species, the methanol extract of C. bornmuelleri, C. gigantea, C. huber-morathii and C. montana were the most toxic extracts in brine shrimp lethality and MTT assay. Arctigenin (IC50=7.0 mM), matairesinol, montamine (IC50=43.9 mM) and lappol A, schischkiniin, arctiopicrin (IC50=8.5 mM) and 8-0-(4-hydroxy-3-methylbutanoyl)-salonitenolide (IC50=26.4 mM) showed higher cytotoxicity against MTT assay. Matairesinoside (IC50=2.2 x 10-3 mg/mL), matairesinol (IC50=2.0 x 10-3 mg/mL) and schischkiniin (lC50=3.8 x 10-3 mg/mL) exhibited significant free radical scavenging activities towards DPPH assay

Antecedents, Wide-Spread Consequences, and Strategic Implications of Organizational Corruption

Antecedents, Wide-spread Consequences, and Strategic Implications of Organizational Corruptio

Effect of thermal annealing and carbon implantation on the functional properties of nanocomposite TiSiN coatings on steel

This PhD research contributes to the part of advanced materials technology. The machining industry currently faces tremendous pressures with the need for durable cutting tools suitable for eco-friendly high speed machining operations becoming acute. In this thesis innovative design and synthesis strategies are explored to tailor the properties of nanocomposite coatings. Advanced characterisation techniques are applied to identify the mechanisms that control the mechanical, tribological, and corrosion behaviours of these coatings. Cutting tools protected by these coatings are anticipated to exhibit a unique combination of superior toughness and greater resistance to wear and corrosion, providing significant economic and environmental benefits. The thin ceramic coatings are commonly applied to various kinds of steel cutting and machining tools to enhance their mechanical and tribological properties. The most common ceramic coating is TiN. But the major issues that hamper the application of TiN are high friction co-efficient (typically~0.5), lower hardness, lower thermal stability (~5000 C) and lower corrosion resistance. To address some of these problems, TiSiN nanocomposite coatings are developed, which have super-hardness, better thermal stability (~10000C) and better corrosion resistance. But the as-deposited TiSiN coating still has high co-efficient of friction (~0.4) and high residual stress (~7-9 GPa) which consequently affect the adhesion and toughness of the coating. This project aims to address these problems by (a) the application of carbon implantation to modify the structure and chemistry of the surface layer of the nanocomposite coatings with reduced friction and residual stress; and (b) thermal annealing of the nanocomposite coating to reduce the residual stress with enhanced fracture toughness, better corrosion resistance and more thermal stability. In addition, the role of microstructure, residual stress and defects of these hard coating in corrosive environment will be studied. For this research, a combination of microstructural and mechanical properties characterization, corrosion analysis, tribological test and finite element modelling facilities will be used. The study includes focused ion beam (FIB) milling and transmission electron microscopy (TEM), Synchrotron X-Ray Diffraction (XRD), X-ray Photo Spectroscopy (XPS), Energy dispersive X-Ray (EDX), nanoindentation, nano-scratching, potentio-dynamic polarization cell and Atomic force microscopy(AFM)

Network tomography application in mobile ad-hoc networks.

The memorability of mobile ad-hoc network (MANET) is the precondition of its management, performance optimization and network resources re-allocations. The traditional network interior measurement technique performs measurement on the nodes or links directly, and obtains the node or link performance through analyzing the measurement sample, which usually is used in the wired networks measurement based on the solid infrastructure. However, MANET is an infrastructure-free, multihop, and self-organized temporary network, comprised of a group of mobile nodes with wireless communication devices. Not only does its topology structure vary with time, but also the communication protocol used in its network layer or data link layer is diverse and non-standard. Specially, with the limitation of node energy and wireless bandwidth, the traditional interior network measurement technique is not suited for the measurement requirement of MANET. In order to solve the problem of interior links performance (such as packet loss rate and delay) measurement in MANET, this dissertation has adopted an external measurement based on network tomography (NT). Being a new measurement technology, NT collects the sample of path performance based on end-to-end measurement to infer the probability distribution of the network logical links performance parameters by using mathematical statistics theory, which neither need any cooperation from internal network, nor dependence from communication protocols, and has the merit of being deployed exibly. Thus from our literature review it can be concluded that Network Tomography technique is adaptable for ad-hoc network measurement. We have the following contribution in the eld of ad-hoc network performance: PLE Algorithm: We developed the PLE algorithm based on EM model, which statistically infer the link performance. Stitching Algorithm: Stitching algorithm is based on the isomorphic properties of a directed graph. The proposed algorithm concatenates the links, which are common over various steady state period and carry forward the ones, which are not. Hence in the process it gives the network performance analysis of the entire network over the observation period. EM routing: EM routing is based on the statistical inference calculated by our PLE algorithm. EM routing provides multiple performance metric such as link delay and hops of all the possible path in various time period in a wireless mesh network

Mathematical model for a heat pump dryer for aromatic plant

A mathematical model was developed to evaluate the performance of heat pump dryer for drying of aromatic plants. The model consists of three sub-models; namely, drying model, heat pump model, and performance model. Drying model was developed based on mass balance, heat balance, heat transfer and drying rate equations. Heat pump sub-model consists of some theoretical and empirical equations for estimating the parameters of evaporator, compressor, condenser and expansion valve. The performance sub-model was the equations for prediction of drying efficiency, COP (coefficient of performance), MER (moisture evaporating rate) and SMER (specific moisture evaporating rate). The model was validated with the experimental data. The experiments was conducted in a fixed bed drying of valerian roots (Valeriana officinalis L.) in cooperation with a agricultural company (Agrargenossenschaft Nöbdenitz e.G., Thüringen) in Thüringen, Germany. Data logger was used to record the temperature, relative humidity, humidity ratio and enthalpy of air at different positions of the dryer equipped with different types of sensors. The average drying air temperature was 36.84°C and relative humidity was about 20%. About 89 hours were required to reduce the moisture content of valerian roots from 89 to 9% (wb). The simulated results (temperature, relative humidity and moisture content) agreed well with the experimental results. The average COP, MER and SMER and drying efficiency were 5.45, 140.03 kg/h, 0.038 kg/kWh, and 78.23%, respectively. This model may be used for design data for heat pump dryer for drying of aromatic plants as well as other heat sensitive crops

Derivati feniloctene kiseline s antioksidativnim učinkom iz sjemenki biljke Ilex aquifolium

Reversed-phase preparative HPLC analysis of the methanol extract of the seeds of Ilex aquifolium afforded two antioxidant phenylacetic acid derivatives, 2,4-dihydroxyphenylacetic acid (1) and 2,4-dihydroxyphenylacetic acid methyl ester (2). The structures were determined by spectroscopic methods. In the DPPH assay for antioxidant activity, the IC50 values of 1 and 2 were 1.50 x 10-3 and 2.55 x 10-3 mg mL-1, respectively, compared to 2.88 x 10-5 mg mL-1 of quercetin, a natural antioxidant.Reverzno-faznom preparativnom HPLC analizom metanolnog ekstrakta sjemenki biljke Ilex aquifolium izolirana su dva derivata feniloctene kiseline s antioksidativnim učinkom, 2,4-dihidroksifeniloctena kisleina (1) i metilni ester 2,4-dihidroksifeniloctene kiseline (2). Njihove strukture određene su spektroskopskim metodama. U DPPH testu na antioksidativno djelovanje, IC50 vrijednosti spojeva 1 i 2 bile su 1.50 x 10-3 i 2.55 x 10-3 mg mL-1, dok je IC50 prirodnog antioksidansa kvercitina bila 2.88 x 10-5 mg mL-1

Awareness and likelihood of accepting COVID-19 vaccines among the university students of Bangladesh

Massive vaccination is very important to end the coronavirus disease 2019 (COVID-19) pandemic. This study determined the willingness to receive a COVID-19 vaccine by the university students of Bangladesh and identified their apprehension about the effectiveness and safety of COVID-19 vaccines. Students were invited to complete an online cross-sectional survey (April 3 to June 10, 2021) to explore the intention to receive a COVID-19 vaccine and other factors regarding the responsiveness of the COVID-19 vaccine. Among the 191 respondent students, 52.9% willingly agreed to receive a vaccine, where the remaining was either not decided yet (27.7%) or was not intended to get vaccinated (15.7%). The odd of getting a vaccine were only 1.15. About 83.2% of students were conscious about the severity of COVID-19 and many students responded that they are well-versed about vaccine activity (67.5%) and risk factors (66%). Among the approved vaccines, most students preferred the Oxford-AstraZeneca COVID-19 vaccine ChAdOx1 (38.7%) and Pfizer-BioNTech COVID-19 vaccine BNT162b2 (34%). As some of the students still have lesser intent to accept vaccines, public health officials need to be more proactive to focus on vaccine safety and benefits to enhance vaccine coverage among university students of Bangladesh

Bioactivity of the extracts and isolation of lignans and a sesquiterpene from the aerial parts of Centaurea pamphylica (Asteraceae).

Centaurea pamphylica Boiss. & Heldr. (Family: Asteraceae), commonly known as 'pamphylia daisy', is a Turkish endemic species of the genus Centaurea that comprises ca. 500 species, many of which have been used as traditional medicines. The n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the aerial parts of C. pamphylica were assessed for antioxidant activity and general toxicity using, respectively, the 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the brine shrimp lethality assays. The reversed-phase preparative HPLC and PTLC were used to isolate compounds from the extracts. The structures of these compounds [1-4] were elucidated by spectroscopic means, and also by direct comparison with the respective published data. Both the DCM and the MeOH extract showed significant levels of antioxidant activities with the RC50 values of 72.6 x 10-2 and 47.3 × 10-2 mg/mL, respectively. The MeOH extract exhibited low levels of toxicity towards brine shrimps (LD50 = 125.0 × 10-2 mg/mL). Three major bioactive components of the MeOH extract were matairesinoside [1], arctiin [2] and matairesinol [3]. An eudesmane-type sesquiterpene, pterodontriol [4], was also isolated from the DCM extract. Since reactive oxygen species are important contributors to various ailments, the antioxidant properties of the extracts as well as the isolated compounds may be of medicinal significance. This is the first report on the occurrence of 1-4 in C. pamphylica, and 4 in the genus Centaurea