Bioactivity of Green Synthesised Silver Nanoparticles

TABLE OF CONTENTS

1 CHAPTER 1 INTRODUCTION

2 CHAPTER 2 METHANOL EXTRACT AND SILVERNANOPARTICLES

3 CHAPTER 3 ACETONE EXTRACT AND SILVERNANOPARTICLES

4 CHAPTER 4 WATER EXTRACT AND SILVERNANOPARTICLES

5 CHAPTER 5 LITERATURE CITED

CHAPTER 1 INTRODUCTION

Research and analysis of nanoparticles (NPs) synthesis and their biological activities has been expanded significantly in the recent years. The agents used for nanoparticles (NPs) synthesis are of organic (mainly carbon) and inorganic (metal ions like silver and gold) origin (Singh et al., 2010). Among these, silver (Ag) is the most preferred NPs synthesis agent due to its reported use in medical field as best topical bactericides from ancient times (Lavanya et a l., 2013). The stable silver nanoparticles had been synthesized by using soluble starch as both the reducing and stabilizing agents (Shrivastava et al., 2012). So the concern of scientific community shifted towards ecofriendly, natural and cheaper method of NPs synthesis by using microorganisms and plant extracts (Mohanpuria et al., 2008). The use of plant materials for silver nanoparticles (AgNPs) is most popular due to its potential biological activities, easy availability and faster rate of synthesis there by cutting the cost of NP's synthesis (Huang et al., 2007 and Salam et al., 2012). The nanoparticles had been clinically used for infection, vaccines and renal diseases (Malhotra et al., 2010). The plant extract of petals of herbal species like Punica granatum, Datura metel (Chandran et al., 2011) and stem extracts of Svensonia hyderobaden sis (Linga et al., 2011) had been effectively used for AgNPs synthesis and investigated for their antimicrobial activities.

Nanoparticles could be synthesized by various approaches like photochemical reactions in reverse micelles (Taleb et al., 1997), thermal decomposition (Esumi et al., 1990), sonochemical (Zhu et al., 2000) and microwave assisted process (Santosh et al., 2002 and Prasher et al., 2009). Nanocrystalline silver particles have found tremendous applications in the field of high sensitivity biomolecular detection and diagnostics (Schultz et al., 2000), antimicrobials and therapeutics (Rai and Yadav., 2009 and Elechiguerra et al., 2005) and micro-electronics (Gittins et al., 2000).

Acacia auriculiformis A. Cunn. is an exotic species that can survive in degraded lands in Thai savanna (Badejo et al., 1998). Besides its high adaptability in degraded savanna areas , A. auriculiformis is known for its nitrogen fixation property (Sprent and Parsons, 2000) enriching macrofaunal composition (Mboukou-Kimbatsa et al., 1998), low allelopathic effects (Bernhard-Reversat et al., 1999) and ability to pump nutrients from the subsoil (Kang et al., 1993). On the other hand, introducing the tree species also introduces constraints like

(1) It is an exotic tree species and thus may result in biological deserts
(2) It may escape to adjacent areas, threatening native species.

Due to the above mentioned constraints, it is questionable whether introducing the exotic species is truly rehabilitative (Hartley et al., 2002). On the other side of the scenario, A. auriculiformis (also called as Black wattle and Australian Kikkar) is an important medicinal plant and widely distributed member of family Fabaceae and subfamily Mimosoideae. It had reported to be a rich source of polyphenols and tannins (Singh et al., 2001). It’s anti-helminthic, anti-filarial and microbicidal effects had been well demonstrated (Gosh et al., 1993 and Mandal et al., 2005). Extensive literature and research of the medicinal as well as biological properties of A. auriculiformis at cellular stage (Du et al., 2007 ), drug delivery (Jong et al., 2008) and diagnostics imaging cancer detection (kairemo et al., 2008) were available in the reports of many scientists. There are no reports available for silver nanoparticles (AgNPs) synthesis using bioactive extracts of important medicinal plant, A. auriculiformis. In the present study, the following objectives had to be explored after green synthesis of AgNPs using extract of A. auriculiformis.

- Characterization of AgNPs with ultra-violet visible spectroscopy (UV-Vis), Fourier Transform Infra-red spectroscopy (FTIR), Photoluminescence spectroscopy (PL) and X-Ray Diffraction spectroscopy (XRD).
- Comparison of antimicrobial activity of crude extract with AgNPs and commercial antibiotics used against Bacillus subtilis, Staphylococcus aureus and Escherchia coli.
- Antioxidant assays to check the efficiency of silver nanoparticles used in disease treatments and chemotherapy by investigating biochemical potential with:
- Total Phenol content estimation.
- Estimation of vitamin C.
- Hydrogen scavenging assay.
- 2, 2 diphenyldrazyl (DPPH) Assay.
- Ferric Thiocyanate method.
- Agarose gel electrophoresis of extract and AgNPs.

The irrational use of chemicals for control of many microbial organisms resulted in development of resistant in these microorganisms. To check the practice of micro fauna control, the concern of scientific community shifted towards the phyto chemicals and green synthesis of silver nanoparticles for enhancement of their bioactivity. Many reports are available with the account of antimicrobial effects of plant extracts along with their silver nanoparticles (AgNPs). In the present chapter, literature reports available on the topic related to green synthesis of nanoparticles and their antimicrobial properties along with characterization of these AgNPs are summarized.

Acacia species

Acacia is the most significant genus of family Fabaceae, first of all described by Linnaeus in 1773 (Table 2.1). It is estimated that there are roughly 1380 species of Acacia worldwide, about two-third of them native to Australia and rest of spread around tropical and subtropical regions of the world (Seigler et al., 2003). The large number of exudate gums obtained from trees of Acacia and certain other families are hetero-polysaccharides and contain similarly bound sugars (D- galactose , L-arabinose and Deoxy-sugar) and uronic acid salts of Na, K, Ca and Mg.

Table 1.1. Taxonomic Position of Acacia auriculiformis

Abbildung in dieser Leseprobe nicht enthalten

Biogenic synthesis of silver nanoparticle

The biosynthesis of nanoparticles (NPs) had received considerable attention due to the growing need to develop environmentally benign technologies in material synthesis (Chatterjee et al., 2012). Synthesis of nanoparticles through biochemical routes, using plant extracts as reducing and capping agents, had received special attention among others, due to maintaining an aseptic environment during the process. Therefore, medicinal plants having well established therapeutic importance are being widely used for the size- and shape-controlled synthesis of silver nanoparticles (Amin et al., 2012). A green method of nanoparticles preparation should be evaluated from these aspects: the solvent, the reducing agent and the stabilized agent (Pandey et al., 2012).

The latest and the most preferred way for synthesis of nanoparticles is green synthesis as it offers one step and eco-friendly way of synthesis of nanoparticles (Kulkarni et al., 2011). The development of reliable green process for the synthesis of silver nanoparticles is an important aspect of current nanotechnology research, since silver has antimicrobial properties. Nanoparticles are used for the preparations of compounds like drugs, vitamins, steroids, proteins flavours, etc. In this project, we had presented a simple and environmental friendly route for the synthesis of silver nanoparticle from silver nitrate salt by utilizing the bark extract of A. auriculiformis and compared its properties with silver nanoparticle (AgNPs).

Green synthesis of Silver nanoparticles and their characterization

Sharma et al. (2007) had synthesized silver nanoparticles using glycine and citric acid as fuel by Solution Combustion Synthesis (SCS). The shape and size of nanoparticles were depending on different oxidant and fuel ratio. The size of nanoparticles were analyzed by X –ray diffraction (XRD) and Ultra violet visible (UV-Vis) absorption spectroscopy.

Baruwati et al. (2009) had promoted green synthesis of silver nanoparticles in water by using microwaves. The characterization was done by using Transmission Electron Microscopy (TEM), XRD and UV-visible spectroscopy. AgNPs served as benign antioxidant that serves as both a reducing and capping agent.

Sivaraman et al. (2009) had synthesized NPs in few seconds at room temperature. Polyphenolic compound and tannic acid derived from plants extracts were used as reducing agent. The size of nanoparticles were analyzed by TEM and UV-visible spectroscopy.

Thirumurugan et al. (2011) had synthesized silver nanoparticles using leaf extracts of Lantana camara. The characterization was done by UV-visible spectroscopy and Scanning Electron microscopy (SEM) to monitor the quantitative formation of silver nanoparticles. Nanoparticles used as spectrally- selective coatings for solar energy absorbance.

Bunghez et al. (2011) had promoted green synthesis of silver nanoparticles from Pelargonium pelatum leaf extract. The characterization was done by using SEM and Fourier Transform Infra- red spectroscopy (FTIR).

Kouvaris et al. (2011) had synthesized silver nanoparticles from leaf extract of Arbutus unedo which acted as a reductant stabilizer .The characterization was done by using FTIR and TEM.

Kulkarni et al. (2011) had synthesized AgNPs from ethanol and water extracts of Anthocerotae, Helianthus annus and Oryza sativa. The characterization was done by SEM and UV-visible spectroscopy.

Kumar and Yadav (2011) had synthesized AgNPs from ethanol and water extracts of Lonicera japonica. The morphology of AgNPs was characterized by FTIR and TEM.

Pandey et al. (2012) had investigated green synthesis of AgNPs by using polysaccharide Cyamopsis tetragonoloba (gaur). The synthesized NPs characterized by FTIR, SEM, TEM and XRD and used for medical diagnosis to detect ammonia level in human.

Kumar et al. (2012) had investigated green synthesis of AgNPs by using leaves of Musa Sapientum. The synthesized AgNPs was characterized by UV-visible spectroscopy and used for medical diagnosis to detect ammonia level in human.

Yadav et al. (2013) had synthesized polyshaped NPs by using leaf extract of Lonicera japonica. The morphology of AgNPs was characterized by SEM, TEM and FTIR.

Antimicrobial activity of AgNPs against bacterial species

Karuppuswamy et al. (2002) had investigated that the ethanol extracts of Balanites aegyptica leaves and stem was useful reducing and capping agent for synthesis of silver nanoparticles which were tested against Bacillus subtili, Escherichia coli and Candida albicans, the higher zone of inhibition (ZOI) with NPs was recorded as compared to extract by taking Ampicillin as a reference antibiotic.

Pal et al. (2007) had reviewed the shaped based antibacterial activity of silver nanoparticles. Scientist explored that the nano scale size and presence of plane combine to promote and enhanced this biocidal property using Gram- negative bacteria, E. coli. The synthesized NPs were characterized by TEM and Energy Filtering TEM.

Kumar et al. (2009) had envisaged the green synthesis of NPs using Cinnamon zeylanicum. The size of AgNPs was determined with XRD, TEM, FTIR and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against E. coli which resulted in conc. based increase in zone of inhibition as compared to methanol extract by taking Erythromycin as a reference antibiotic. The AgNPs were reported to completely inhibit the growth of E. coli.

Prabhu et al. (2010) had synthesized silver nanoparticles from herbal species (Ocimum sanctum and Vitex negunda) and assessed their anti-microbial activity. The anti-bacterial activity of AgNPs was checked against various bacterial cultures viz; S. aureus, P. aeruginosa and Proteus vulgaris. The ZOI were more in O. sanctum as compared to V. negunda.

Govindaraju et al. (2010) had investigated the green synthesis of AgNPs by Solanum torvum and were analyzed by TEM, SEM and UV-visible spectroscopy. The antimicrobial activity was assessed against E. coli and S. aureus. The AgNPs resulted in higher ZOI against E. coli as compared to methanol extract.

Khandelwal et al. (2010) had synthesized the AgNPs from plant extract of Argimone mexicana and the morphology was characterized by XRD, FTIR, SEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was assessed against E. coli, B. subtilis and P. aeruginosa by taking Cholaramphenicol as a reference antibiotic, which resulted in conc. based increase in ZOI and highly toxic against these pathogens as compared to methanol extract.

Kaler et al. (2010 ) had synthesized silver nanoparticles by plants polysaccharides and Tollens. The characterization of AgNPs was done by UV-visible spectroscopy. The anti-bacterial activity was checked against E. coli, S. aureus and Bacillus species . The AgNPs enhanced zone of inhibition as compared to methanol extract.

Priya et al. (2011) had envisaged the synthesis the silver nanoparticles from Euphorbia hirta and Nerium indicum. The morphology of AgNPs was characterized by FTIR, SEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was tested against Gram-positive bacteria B. subtilis, S. aureus and Gram-negative bacteria E. coli, K. pneumoniae. The AgNPs had showed higher ZOI and had good potential of inhibiting the growth of bacteria as compared to methanol extract .

Ray et al. (2011) had envisaged the green synthesis of NPs from Tricholoma cras sium and the AgNPs were characterized by TEM and SEM. The antibacterial activity of AgNPs was checked against E. coli and plant pathogenic bacteria Agrobacterium tumifaciens by taking Chloramphenicol and Rifamycin as a reference antibiotic. The increased conc. of AgNPs had shown remarkable ZOI as compared to methanol extract. The AgNPs showed potent inhibitory effect on these pathogenic bacteria.

Banu et al. (2011) had synthesized the phyto silver nanoparticles from extract of Cleome viscosa. The AgNPs were characterized by FTIR, XRD, TEM and SEM analysis. The anti-microbial activity was assessed against E. coli, S. aureus and P. aeruginosa. The AgNPs resulted in inhibiting the growth of bacteria more effectively as compared to methanol extract.

Kannan and Subbalaxmi (2011) had envisaged the green synthesis of silver nanoparticles using bacterial extracts from Bacillus species and analyzed by them with UV-visible and Laser diffractometery. The bioactivity of AgNPs was checked against E. coli and Staphylococcus epidermidis which exhibited clearly enhanced inhibition zone than methanol extract.

Chauhan et al. (2011) had developed a green synthesis method for nanoparticles using Pomegranates seeds. The morphology of nanoparticles was characterized by XRD and TEM. The anti-bacterial assays of silver nanoparticles were checked against human pathogen E .coli by food poisoning and disc diffusion method. The synthesized nanoparticles showed remarkable zone of inhibition for pathogens when compared with methanol extract by taking Streptomycin as a reference antibiotic.

Benjamin and Bharathwag (2011) had used Allium cepa (Onion) extracts for the synthesis of silver nanoparticles. The synthesized nanoparticles were characterized with UV-visible spectroscopy. The nanoparticles showed significant anti-bacterial activity against E. coli and also showed anti-oxidant activity. The NPs were also showed anti carcinogenic activity.

Anand et al. (2011) investigated green synthesis of AgNPs by using Avicennia marine, mangrove plant and were characterized by FTIR. The antibacterial activity of AgNPs was performed by using E. coli and S. aureus. The synthesized NPs were resulted as potential antibacterial agents and enhanced the antibacterial growth.

Chaghaby et al. (2011) had synthesized NPs from Pistacia lentisus, an evergreen shrub of Anocardiaceae family and NPs were analyzed by XRD, TEM and UV-visible spectroscopy. The antibacterial activity was checked against bacterial species S. aureus and Strepyococcus faecalis. The AgNPs exhibited higher ZOI in bacterial strains as compared to methanol extract.

Bonde et al. (2011) had investigated green synthesis of AgNPs from Foeniculum vulgare (saunf). AgNPs were analyzed by NTA (Nano tracking and analysis) and UV-visible spectroscopy. The antibacterial activity of AgNPs was tested by combining NPs with vancomycin against E. coli and S. aureus. The AgNPs exhibited higher and clear zone of inhibition in E. coli.

Srivastava et al. (2011) had synthesized the AgNPs from methanol and ethanolic extract of Fissidens minutus (Bryophytes) and characterized by SEM and EDS. The AgNPs had increased inhibiting potential and the antibacterial activity against E. coli, B. subtilis, P. aeruginosa and K. pneumoniae. The AgNPs exhibited higher ZOI as compared to methanol extract.

Savithramma et al. (2011) had envisaged the green synthesis of AgNPs from stem extract of Boswellia ovalifoliolata (medicinal plant). The morphology of AgNPs was characterized by SEM, EDX and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against bacterial species P. aeruginosa, P. vulgaris, K. pneumoniae and E. coli. The AgNPs exhibited higher ZOI as compared methanol extract by taking Erythromycin as an antibiotic.

Mahitha et al. (2011) had synthesized the AgNPs from plant extract of Bacopa monniera and the morphology was characterized by XRD, TEM and EDX. The antibacterial activity of AgNPs was assessed against E. coli, B. subtilis, S. aureus and K. pneumoniae which resulted in conc. based increase in ZOI as compared to methanol extract.

Koperuncholan et al. (2011) had envisaged the synthesis the silver nanoparticles from Myristica dactyloides. The morphology of AgNPs was characterized by FTIR, XRD and UV-visible spectroscopy. The antibacterial activity of NPs was tested against Gram-positive bacteria, B. subtilis, S.aureus and Gram-negative bacteria, E. coli, K. pneumoniae. The AgNPs had showed higher ZOI and had good potential of inhibiting the growth of bacteria as compared to methanol extract.

Narashimha et al. (2011) had envisaged the green synthesis of NPs from Agaricus bispons. The size of AgNPs was analyzed by FTIR, TEM and X-ray diffraction. The antibacterial activity of AgNPs was checked against S. aureus, E. coli and P. aeruginosa which resulted in conc. based increase in ZOI as compared to methanol extract by taking Ampicillin as reference antibiotic.

Huang et al. (2011) had envisaged the green synthesis of NPs from Cacumen patyclodi and the AgNPs were characterized by XRD, TEM, Selected-area diffraction (SAED) and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against S. aureus and E. coli. The increased conc. of AgNPs had shown remarkable ZOI as compared to methanol extract. The AgNPs completely inhibited E. coli and had insignificant effect on S. aureus.

Gnanadesigan et al. (2011) had envisaged the green synthesis of NPs from leaves and bark of Avicennia marina (mangrove plant). The morphology of NPs was characterized by FTIR and XRD. The bioactivity of AgNPs was checked against E. coli, P. aeruginosa, S. aureus and B. subtilis. E. coli had exhibited higher ZOI when compared to methanol extract by taking Erythromycin as a reference antibiotic.

Kariuki and Njoroge (2011) tested extracts of A. nilotica against three test organism; S. aureus, S. pneumoniae and E. coli for their antimicrobial properties using the disk diffusion method.

Mahmood et al. (2012) investigated antimicrobial activities of crude methanolic extract of leaves of A. nilotica using agar well diffusion method against one Gram positive bacteria B. subtilis and three Gram negative bacteria, P. aeruginosa, E. coli and K. pneumoniae. These results showed that plant extract have potential against bacteria.

Jena et al. (2012) had reported green synthesis of AgNPs by using algae Chlorococcum humicola. The synthesized AgNPs were characterized by TEM, SEM, XRD and FTIR. The antimicrobial activity was performed by using E. coli and AgNPs resulted in inhibited growth of bacteria more effectively as compared to methanol extract.

Nagaventaka et al. (2012) had synthesized silver nanoparticles from Polylthia longifolia, an evergreen tree and analyzed AgNPs by UV-visible and TEM. The antimicrobial activity was checked against S. aureus, E. coli and Bacillus cereus. AgNPs showed remarkable growth inhibition as compared to methanol extract by taking chloramphenicol as a reference antibiotic.

Nagat et al. (2012) had envisaged synthesis of silver nanoparticles from Cajanus cajan (pigeon pea) leaf extract and AgNPs were characterized with UV-visible spectroscopy, FTIR, SEM and High resolution TEM. The antibacterial assays were done against E. coli and S. aureus. The synthesized nanoparticles showed higher ZOI against both Gram positive and Gram negative bacteria.

Nethradevi et al. (2012) had investigated green synthesis of nanoparticles by Datura metel flower. The size of synthesized nanoparticle was determined by SEM, FTIR and UV-visible spectroscopy. Anti-microbial assays were performed for pathogenic micro-organisms, Micrococcus luteus, S. aureus, E. coli and K. pneumoniae. The synthesized nanoparticles exhibited remarkable ZOI against E .coli as compared to methanol extract and Streptomycin.

Nagaraj et al. (2012) had investigated the green synthesis of NPs from Caesalpina pulcherrima (peacock flower). The size of AgNPs was analyzed by TEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against Streptobacillus species and E. coli which resulted in conc. based increase in ZOI as compared to methanol extract by taking Ampicillin as reference antibiotic.

Maheswari et al. (2012) had envisaged the synthesis the silver nanoparticles from Dioscore oppositifolia. The morphology of AgNPs was characterized by FTIR, TEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was tested against B. cereus, S. typhi, E. coli, P. aeruginosa and E. faecalis. The AgNPs had showed higher ZOI and had good potential of inhibiting the growth of bacteria as compared to methanol extract.

Karthiga et al. (2012) had investigated the green synthesis of NPs from Garcinia mangostana and the size of AgNPs was analyzed by XRD, FTIR and UV-visible spectroscopy. The antibacterial activity of AgNPs were checked against B. subtilis and E. coli which resulted in conc. based increase in ZOI as compared to methanol extract by taking Ampicillin as reference antibiotic.

Raj et al. (2012) synthesized nanoparticles by using the leaf extract of Aristolochia bracteata. The morphology of nanoparticles was analyzed by FTIR, XRD and UV-visible spectroscopy methods. The anti-bacterial activity was checked against S. aureus, Micrococcus luteus and K. pneuoniae. The Bracteata species showed good anti-bacterial action against Gram positive species than gram negative species. The silver nanoparticles combined with Tetracycline and showed good anti-bacterial effect against Vibrio cholereo.

Sarkar et al. (2012) had synthesized silver nanoparticles from leaves of Cedrus deodar. The nanoparticles size was analyzed by UV-visible spectroscopy and TEM. The antimicrobial assay was done against Aeromonas hydrophila (Gram negative), a plant pathogen.

Solgi and Taghizadeh (2012) had envisaged the green synthesis of silver nanoparticles from two medicinal plants Punica granatum and petals extract of Rosa damasana. The qualitative nature of AgNPs was analyzed by SEM, XRD, FTIR and UV-visible spectroscopy. The anti-bacterial activity was tested against S. aureus, M. luteus and K. pneuoniae. The AgNPs exhibited good antibacterial action both against Gram positive species and Gram negative species as compared to methanol extracts.

Rao and Savithramma (2012) had synthesized silver nanoparticles using stem extract of Svensonia hyderabadensis. The characterization of AgNPs was done by UV-visible spectroscopy. The synthesized nanoparticles were tested against E. coli and Bacillus. AgNPs showed remarkable ZOI against bacterial species.

Alagumuthu and Kirubha (2012) investigated green synthesis of AgNPs by using Cissus quadrangularis plant extract and qualitative nature of AgNPs was characterized by FTIR, SEM and UV-visible spectroscopy. The antimicrobial activity was tested against E. coli, B. subtilis, S. aureus and P. aeruginosa. The synthesized NPs were found highly toxic against different multidrug resistant human pathogen and exhibited higher ZOI in E. coli when compared to methanol extract.

Awwad et al. (2012) envisaged the green synthesis of nanoparticles by using Mulberry leaves extract and the morphology of AgNPs was characterized by SEM, XRD and UV-visible spectroscopy. The antimicrobial activity was checked against S. aureus and Shigella species. The synthesized NPs exhibited higher zone of inhibition than pure plant extract.

Bonde et al. (2012) had synthesized AgNPs from leaf extract of Murraya koenigii (Indian curry leaf). The characterization of AgNPs was done by FTIR and UV-visible spectroscopy. The antimicrobial activity of AgNPs showed remarkable zone of inhibition against E. coli, S. aureus and P. aeruginosa, when used in combination with antibiotics like Tetracycline and Gentamicin.

Gavhane et al. (2012) reported green synthesis of AgNPs by using Neem and Triphala leaves. The synthesized AgNPs was characterized by TEM and NTA (nanoparticle tracking analyser measurement). The AgNPs showed remarkable ZOI against E. coli, S. typhi, K. pnumenoiae and Candida albicans as compared to methanol extract.

Shekhawat et al. (2012) had envisaged the green synthesis of AgNPs from leaf extract of Turnera ulmifolia. The AgNPs were characterized by UV-visible spectroscopy. The antimicrobial activity was performed against S. aureus, E. coli, P. aeroginosa and E. faecalis. The AgNPs showed higher ZOI against E. coli and P. areuginosa.

Amin et al. (2012) had reported the synthesis of nanoparticles from methanol extract of Solanum xanthocerpum berry. The morphology of AgNPs was characterized by TEM and UV-visible spectroscopy. The AgNPs were tested against Helicobacter pylori and higher zone of inhibition was observed as compared to methanol extract by taking a reference antibiotic Amixillin.

Kudle et al. (2012) had investigated Cuminum cyminum species for synthesis of silver nanoparticles by using microwave irradiation method and characterized the synthesized nanoparticles by FTIR , UV-visible spectroscopy, SEM, TEM and XRD. Anti-bacterial assays were checked against pathogenic microorganisms, P. putida, E. coli, B. subtilis and S.aureus by taking Ampicillin as a reference antibiotic. The results concluded that AgNPs showed remarkable ZOI than methanol extract.

Awwad et al. (2012) investigated biosynthesis of nanoparticles from Olea europaea leaf extract and the qualitative characterization was done by XRD, SEM, FTIR, SPR (surface plasmon resonance) and UV-visible spectroscopy. The antimicrobial activity of AgNPs was checked against S. aureus, Shigella and Listeria monocytogenes. The remarkable zone of inhibition of AgNPs was found in L. monocytogenes as compared to pure methanol extract.

Krishnamoorthy et al. (2012) had synthesized silver nanoparticles from leaves of Phyllanthusniruri and characterized AgNPs with TEM, FTIR and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against S. aureus, B. subtilis and S. typhi. The S. typhi exhibited remarkable ZOI as compare to methanol extract.

Chaudhari e t al. (2012) had reported the synthesis of NPs using supernatant of Lactobacillus strain streaked by Vizylac capsule. The characterization was done by TEM, EDX (Energy dispersive X-ray) and NTD (Nano particle analyzer). The antimicrobial activity was checked against bacterial species K. pneumoniae and S. typhi by taking Ampicillin as control. The AgNPs exhibited higher ZOI as compared to methanol extract .

Ghosh et al. (2012) had synthesized NPs from Dioscorea bulbifera (rich in flavonoids, ascorbic and citric acid). Bulbifera species had synergistic potential for enhancement of antibacterial activity. The characterization was done by TEM, HR-TEM (Higher resolution) and XRD. The AgNPs exhibited higher cytotoxicity against E. coli and K. pneumoniae and less activity shown for S. aureus when compared to methanol extract by taking a reference antibiotic Gentamicin.

Geoprincy et al. (2012) had synthesized AgNPs from Aavi leaf. The size of AgNPs was characterized by UV and EDAX. The antimicrobial activity of AgNPs was checked against bacterial species S . aureus, M. luteus, E. coli and S. typhi, which resulted in conc. based increase in ZOI as compared to methanol extract by taking Erythromycin as a reference antibiotic.

Ojha et al. (2012) had synthesized AgNPs from plant extract of Syzygium aromaticum (family Lauraceae) and the morphology of NPs was characterized by using SEM, TEM and UV-visible spectroscopy. The antibacterial activity was checked against bacterial species S. aureus, E. coli and S. typhi. The AgNPs exhibited higher ZOI as compared to methanol extract.

Malabadi et al. (2012a) had envisaged the green synthesis of NPs from Clitoria ternatea and the size of AgNPs was analyzed by using SEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against S. aureus, E. coli and K. pneumoniae and exhibited remarkable ZOI as compared to methanol extract.

Malabadi et al. (2012b) had envisaged the green synthesis of NPs from Catharoanthus roseus. The size of AgNPs was characterized by using SEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against S. aureus, E. coli and B. subtilis, which resulted in conc. based increase in zone of inhibition as compared to methanol extract.

Kora et al. (2012) had envisaged the green synthesis of NPs from gum (ghatti) Anogeissus latifolia. The size of AgNPs was characterized by using TEM, UV-visible spectroscopy, FTIR and X-ray diffraction. The antibacterial activity of AgNPs was checked against S. aureus, E. coli, P. aeruginosa and AgNPs exhibited remarkable ZOI as compared to methanol extract by taking reference antibiotic Tetracycline.

Prakash et al. (2012) had envisaged the green synthesis of NPs from Vinca roseus and the qualitative nature of AgNPs was analyzed by using XRD, SEM and UV-visible spectroscopy. The antibacterial activity of AgNPs was checked against S. aureus, E. coli, P. aeruginosa and B. subtilis, which resulted in conc. based increase in zone of inhibition as compared to methanol extract.

Sable et al. (2012) had synthesized AgNPs from leaf extract of Foeniculum vulgare. The morphology of AgNPs was characterized by using particle size measurement and UV-visible spectroscopy. The antibacterial activity AgNPs was checked against bacterial species S. aureus and E. coli, which exhibited clear and higher ZOI as compared to methanol extract.

Geethalakshmi and Sarada (2012) had envisaged the green synthesis of NPs from plant extract of Trianthema decandra. The size of AgNPs was determined by using UV-visible spectroscopy, FTIR and FE-SEM (Field emission scanning electron microscopy). The antibacterial activity and ZOI was effectively increased against S. aureus, E. coli, P. aeruginosa and S. faecalis as compared to methanol extract.

Jagtap et al. (2012) had synthesized AgNPs from leaf extract of Annoma squamosal at room temperature. The morphology of AgNPs was characterized by using Particle size measurement, UV-visible spectroscopy, FTIR and FEG-SEM (Field emission scanning electron microscopy). The antibacterial activity of AgNPs was checked against S. aureus, E. coli and K. pneumoniae which showed remarkable ZOI for E. coli as compared with methanol extract by taking Vancomycin as a reference antibiotic.

Rajesh et al. (2012) had reported the green synthesis of AgNPs from a ethyl acetate extract of marine algae Ulva fasciata (Delile). The morphology of NPs was analyzed by EDAX and FTIR. The nanoparticles were tested against bacterial species effectively and inhibit the growth and reproduction of Xanthomonas compestrris bacteria more effectively as compared to crude methanol extract.

Devi and Bhima (2012) had synthesized AgNPs from the sea weed Ulva lactuca. The characterization was analyzed by EDAX, XRD, TEM and FTIR. The synthesized nanoparticles were tested for its efficiency as a potent cytotoxic agent against human cancer cell lines.

Saxena et al. (2012) had envisaged the green synthesis of NPs from plant extract of Ficus benghalensis. The size of AgNPs was characterized by UV-visible spectroscopy, Dynamic light scattering and Atomic force microscope. The antibacterial activity of AgNPs was effectively enhanced the ZOI in E. coli by colony forming unit (CFU).

Dhanalakshmi et al. (2012) had envisaged the green synthesis of NPs from plant extract of Tridax procumbens and the qualitative nature of AgNPs was characterized by UV-visible spectroscopy and SEM. The antibacterial activity of AgNPs was checked against Salmonella typhi, E. coli and Shigella species which resulted in conc. based increase in ZOI as compared to methanol extract by taking Tetracycline as a reference antibiotic.

Baishya et al. (2012) had envisaged the green synthesis of NPs from Brophyllum pinnatum and qualitative nature of AgNPs was characterized by XRD, TEM, FTIR, SEM and UV-visible spectroscopy. The bioactivity of AgNPs was checked against S. aureus and E. coli. The increased conc. of NPs had shown remarkable zone of inhibition as compared to methanol extract. The AgNPs completely inhibited growth of E. coli and had insignificant effect on S. aureus.

Daniel et al. (2012) had envisaged the green synthesis of NPs from Eichornia crassipes (aquatic weed). The size of AgNPs was analyzed by using TEM, FTIR and Atomic force Microscopy and antibacterial activity of NPs was checked against B. subtilis and K. pneumoniae. The AgNPs had shown higher ZOI by taking a reference antibiotic Streptomycin whereas methanol extract showed no antibacterial activity.

Gnanajobita et al. (2013) had reported green synthesis of AgNPs by using flower extract of Millingtonia hortensis. The synthesized AgNPs were characterized by SEM and FTIR. The antimicrobial activity of AgNPs was observed by using cultures of B. subtilis and K. planticola. The AgNPs exhibited remarkable ZOI and used to develop nano-medicine against different human pathogen.

Kudle et al. (2013) had investigated green synthesis of AgNPs using Stigmaphyllon littorale leaves. The characterization of AgNPs was done by TEM, SEM, FTIR and UV- spectroscopy. The antimicrobial activity was performed against P. putida, E. coli, B. subtilis and M. luteus. AgNPs showed remarkable zone of inhibition as compared to methanol extract.

Lavanya et al. (2013) had studied green synthesis of AgNPs using leaf extract of Paederia foetida and morphology of AgNPs was analyzed by XRD, FTIR, SEM and UV-visible spectroscopy. The antimicrobial activity was checked against S. aureus, Klebsiella sp., P. aeruginosa and E. coli. The klebsiella sp. and P. aeruginosa showed higher zone of inhibition as compared to methanol extracts.

Roy et al. (2013) had studied green synthesis of AgNPs from fruit extract of Vitis vinifera (grape ) and were characterized by TEM, Dynamic light scattering (DLS) and Energy dispersive X-ray spectroscopy) EDX. The antimicrobial activity was performed against E. coli and B. subtilis. The clear and remarkably increased ZOI was showed with AgNPs as compared to methanol extract.

Pratima et al. (2013) had reported biosynthesis of AgNPs using cabbage broth. The synthesized NPs were characterized by XRD and UV-visible spectroscopy. The antimicrobial activity tested against B. subtilis, E. coli, Klebsiella sp and S. aureus. The AgNPs showed remarkable ZOI as compared to methanol extract.

Gopinath et al. (2013) had envisaged the green synthesis of NPs from legume Cissus quadrangulari. The size of AgNPs was determined by using XRD, EDAX, HR-TEM and FTIR. The antibacterial activity of AgNPs was checked against Gram negative bacteria E. coli and Gram positive bacteria S. aureus. The AgNPs had showed higher ZOI in both type of bacteria as compared to methanol extracts.

Komal and Arya (2013) had studied green synthesis of AgNPs using aqueous leaf extract of Carica papaya. The characterization was done by TEM and UV-visible spectroscopy. The bioactivity of AgNPs was checked against Enterococcus, P. aeruginosa, K. pneumoniae and E. coli. The AgNPs showed higher zone of inhibition as compared to methanol extract.

Sivaranjani et al. (2013) had synthesized of NPs from medicinal plant Ocium basillicum. The morphology of NPs was characterized by SEM, FTIR, XRD and UV-visible spectroscopy. The bioactivity activity of AgNPs was checked against E. coli, P. aeruginosa and B. subtilis. P. aeruginosa had exhibited higher ZOI whereas E. coli and B. subtilis showed negative inhibition when compared to methanol extract by taking Erythromycin as a reference antibiotic.

Antioxidant activities of NPs and extracts

Naik et al. (2003) examined Momardica charantia Linn, Glycyrrhiza glabra, Acacia catechu and Terminalia chebula as antioxidants. The results were found to be in agreement with the lipid peroxidation data showed maximum value of ascorbate equivalent.

Kaur et al. (2002a and 2002b) provided a correlation of the antimutagenic and chemopreventive activity of the barks of two commonly observed plants viz; A. auriculiformis and Acacia nilotica using the Ames antimutagenicity assay and the mouse mammary gland organ culture (MMOC) model. These results exhibited good correlation between the antimutagenesis assay and the MMOC model, suggesting that these plants may contain active chemopreventive agents. The activity of A. nilotica extract may be partially due to the presence of gallic acid and other polyphenols.

Singh et al. (2007a; 2007b and 2007c) had evaluated the antioxidant potential of ethyl acetate extract of A. auriculiformis. The inhibitory potential was compared with known antioxidants like ascorbic acid, calculated attenuation of free radicals by acetone extract and evaluated the DPPH and Free Radical Scavenging Assays of acetone extract of A. auriculiformis and antioxidant potential of methanol extracts of A. auriculiformis. The inhibitory potential was compared with known antioxidants like ascorbic acid.

Ali et al. (2008) reviewed Indian medicinal herbs Amaranthus paniculatus, Aerva lanata, Coccinia indica and Coriandrum sativum indicating that plants could be source of dietary antioxidant supplies.

Bakar et al. (2009) evaluated antioxidant activity of different parts of Mangifera pajang and Artocarpus odoratissimus. The results showed that kernel and peel from pajang contained a broad range of polyphenol phytochemicals which might be responsible for the cytotoxicity activity against selected cancer cell line.

Chan et al. (2009) assessed antioxidant properties of leaves and tea of ginger species. All methods of thermal drying (microwave, oven, and sun-drying) resulted in drastic declines in total phenolic content (TPC), ascorbic acid equivalent antioxidant capacity (AEAC), and ferric-reducing power (FRP), with minimal effects on ferrous ion-chelating ability and lipid peroxidation inhibition activity.

Lin et al. (2009) assessed antioxidant property of buckwheat enhanced wheat bread. The results showed that it had good antioxidant activity, reducing power and 1,1-diphenyl-2- picrylhydrazyl radical scavenging ability..

Zhang et al. (2009) studied antioxidant phenolic compounds from Juglans regia L. The results of this study suggested that the antioxidant activities of these phenolic compounds may be influenced by the number of hydroxyls in their aromatic rings.

Velvan et al. (2012) had synthesized silver nanoparticles using Cassia auriculata flower and AgNPs were analyzed by SEM and UV-visible spectroscopy. The synthesized nanoparticles had some effective anti-oxidant activity against various in vitro anti-oxidant systems. The anti-oxidant activity was determined by performing assays like Free radical scavenging assay and Iron reducing power assay

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