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Volume 1, December 2016, pages 29-34

Antimicrobial activities of silver nanoparticles synthesized from peel of fruits and vegetables

Abhay Tripathi1*, Rupa Sirohi1

1*Department of Biotechnology, Meerut Institute of Engineering and Technology, Meerut, Uttar Pradesh, India
* Corresponding Author Email: abhaymiet05@gmail.com | Tel: +917417620463

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Abstract

Biological nanoparticles from peel of fruits of Mango (Mangifera indica), Papaya (Carica papaya) & Pomegranate (Punica granatum) and vegetables, Bottle gourd (Lagenaria siceraria), Cucumber (Cucumis sativus) & Potato (Solanum tuberosum) were synthesized. Synthesis of AgNPs was confirmed by UV-VIS absorption spectroscopy and plasmon peak maxima was observed at 425nm, 435nm, 450nm for fruits peel of mango, papaya and pomegranate respectively. On the other hand, at 455nm, 420nm, 430nm for vegetables peel of bottle gourd, cucumber and potato respectively. The antimicrobial activity was studied by agar well diffusion method  on Muller Hinton agar medium. The antimicrobial activities of AgNPs synthesized from fruits and vegetables peel concentration at  100µg/ml was checked against seven pathogens B. subtilis, B. pumilis, E. coli, K. pneumoniae, S. aureus, A. niger and C. tropicalis.AgNPs synthesized from fruits and vegetables exhibited significant antimicrobial activities against all pathogens involved in our study.

Keywords

Nanoparticles,  Antimicrobial activity, UV-Visible spectroscopy,  Fruit peel, Vegetable peel,  Pathogens

Introduction

Infectious diseases are leading cause of death worldwide due to multidrug resistant strains of bacteria, reduced susceptibility to antimicrobics and increase in untreatable microbial infections. Natural products provide unlimited opportunities for new drug leads because of their unmatched availability of chemical diversity. In the increasing threat of infectious diseases, the need of the hour is to find out natural agents with novel mechanism of action to counter the diseases. Fruit and vegetable peels are thrown into the environment as agro waste which can be utilized as a source of antimicrobics. Screening of plants with validated methods can lead to identify potentially useful molecules against infectious diseases.
Silver nanoparticles have been recently known to be a promising antimicrobial agent that acts on a broad range of target sites both extracellularly as well as intracellularly. Silver nanoparticles shows very strong bactericidal activity against gram positive as well as gram negative bacteria including multi resistant strains (Aviram et al. 2002). The development of consistent processes for the synthesis of silver nanomaterials is an important aspect   of current nanotechnology research. One of such promising process is green synthesis (Calzada et al. 2007). Crude extracts from fruits & vegetables peel act as a green reactant for Ag Nanoparticles synthesis (Shankar et    al. 2003).
In the, present investigation, we have reported the antimicrobial properties of peel of different fruits and vegetables and evaluated the role of silver nanoparticles synthesized from peels as an antimicrobial agent and whether they can  become an alternative source of natural antimicrobics.

Materials and Methods

2.1. Materials
Silver nitrate (AgNO3, 99.995%) was purchased from Merck India. Fruits and vegetables peels of Mango (Mangifera indica), Papaya (Carica papaya), Pomegranate (Punica granatum), Bottle gourd (Lagenaria siceraria), Cucumber (Cucumis sativus) & Potato (Solanum tuberosum) were collected from local market. It was washed  with deionized water and then dried in sunlight for 10-15 days. All glassware was washed and rinsed with deionized water, followed by subsequent drying.
2.2. Microorganisms used
Microorganisms were procured from the MTCC located at the Institute of Microbial Technology (IMTECH) Chandigarh, India as a lyophilized culture. Microorganisms used for this study were Bacillus  subtilis,  Bacillus  pumillis, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Aspergilus niger, Candida. tropicalis.
2.3. Preparation of peel extract
The dried fruits and vegetables peel were powdered and stored in containers  for  the  synthesis  of  silver  nanoparticles. 25 g of peels were boiled at 60oC in 100 ml deionized water for 30 min. After boiling, the color of        the   aqueous   solution  changed   from   colorless   to  light   and   dark   yellow  colors.  The  aqueous   extracts   were separated by filtration  with Whatmann No. 1 filter  paper (pore size 0.45 µm) and then centrifuged at 1000 rpm  for   10 min to remove heavy   biomaterials.
2.4. Synthesis of silver nanoparticles
Aqueous solution of 1mM silver nitrate (AgNO3) was prepared and used for the synthesis of silver nanoparticles. 10 ml of peel extracts of each sample was added into 90 ml of aqueous solution of 1 mM silver nitrate for reduction into Ag+ and kept for incubation period of 15 hr at room temperature. Here the filtrate acts as reducing and stabilizing agent for 1 mM of AgNO3. The formation of silver nanoparticles was confirmed by color change from yellow to grey in mango and pomegranate, light yellow to blackish brown in papaya fruits peel, yellow to blackish brown in potato and bottle gourd, light yellow to dark brown in cucumber vegetable peels.
2.5. UV-VIS spectroscopy
The Ag nanoparticles were characterized using UV-VIS Spectrophotometer V-530 JASCO. The scanning range for the samples was 300-800 nm. Double distilled water used as a blank reference.
2.6. Antimicrobial activity test
The antimicrobial activity testing was done using the Agar well diffusion method to detect the presence of  anti microbial activity of the plant extracts.  Muller Hinton agar was poured into petri dishes. After solidification test   strains were uniformly spread over the media.  The  test  sample  was  introduced  into  well  and  plates  were  incubated at 37°C for 48 hrs. All samples  were  tested  in  triplicates.  Bacterial  growth  was  determined  by  measuring the zone of inhibition in  mm.

Results and Discussions

3.1. Synthesis of AgNPs
The synthesis of  silver nanoparticles through fruits and vegetables peel  extracts were carried out by mixing the      plant extracts of fruits and vegetables peel with 1mM silver nitrate solution a change in the color from yellow to      grey in mango and pomegranate, light yellow to blackish brown in papaya fruits peel, yellow to blackish brown in potato  and  bottle  gourd,  light  yellow  to  dark  brown  in  cucumber  vegetable  peels  were  observed  (Figure 1&2). Similar results were also reported by  many researchers  (Tyagi  et  al.  2012).  The  changed  color  confirms  that  it was due to the reduction of Ag+ which indicates the formation of Ag NPs.
3.2. UV–VIS spectral analysis
In our results peak specific for the synthesis of silver nanoparticles was obtained at 420-455 nm by UV Visible spectroscope in the form of a sharp peak (Figure 3), which was specific for the synthesis of AgNPs. The absorption peak maximum is attributed to the scattering by silver metal (Kapoor 1998). The appearance of grey, blackish brown and dark brown color indicates the formation of silver nanoparticles in the reaction mixture. However, silver nanoparticles exhibit striking color (yellow to brown) due to the excitation of surface plasmon vibration in the particles. The presence of single sharp peaks on average 425nm in all samples indicating that the silver nanoparticles are spherical in shape.
3.3. Antimicrobial activity
The antimicrobial activities  were observed for both the samples of fruits and vegetables. Antimicrobial activities of   the synthesized AgNPs were determined, using the well diffusion method (Elumalai et al. 2010).  The  plates  containing the test organism and AgNPs were incubated at 370C for 24 - 48 h.  The  plates  were  examined  for evidence of zones of inhibition, the diameters of such zones of inhibitions were measured using a meter ruler and the mean value for each organism was recorded and expressed in millimeter. The antimicrobial activity of AgNPs synthesis from fruits and vegetables peel concentration  100µg/ml  were  checked  against  seven  pathogens  B.  subtilis, B. pumilis, E. coli, K. pneumonia, S. aureus, A. niger and C. tropicalis. The  zone  of  inhibition  (mm diameter) were observed in fruits peel with the range from 4.0 to 6.0 for mango, 4.0 to 8.5 for papaya, 5.5 to 8.5         for pomegranate, and in vegetables peel 6.5 to 9.5 for bottle gourd, 6.0 to 10.0 for cucumber, 7.0 to 9.5 for potatoagainst pathogens B. subtilis, B. pumilus, E. coli, K. pneumonia, S. aureus, A. niger and C. tropicalis respectively (Table 1 & Figure 5, 6). On the other hand, the antimicrobial activity comparison (in %) between fruits peel vs vegetables peel the maximum zone of inhibition 18% of B. pumilis were found in fruits peel (papaya  and  pomegranate) and minimum 9% of S. aureus in  papaya. While,  16-18%  of  B.  subtilis  were found in  vegetables  peel (bottle guard, cucumber and  potato) and minimum  11% of  S. aureus  in cucumber (Figure    4).
These fruits and vegetables are used in modern herbal medicine and they also help  in  overcoming  depression, protecting against heart ailments, providing relief from stomach disorder, reducing risk of developing cancer, providing youthful and glowing skins,in reducing symptoms of anemia. These fruits peels contain compounds that especially help to support and modulate hormones and hormonal balance .Fruits and vegitables peel is primarily composed of alkaloids, ascorbic acids and polyphenols. The active constituent that appears to be responsible for its multiple health benefits is ellagic acids. Ellagic acid is a naturally occurring compound found in several fruits and nuts. The ellagic acid effectively protects cells from damaging free radicals (Ahmad et al. 2012). The mechanism of the bactericidal effect of silver nanoparticles is not very well- known. It is believed that cellular proteins become inactive after treatment with silver nanoparticles (Fresta et al. 1995). It is also believed that silver nanoparticles after penetration into the bacteria have inactivated their enzymes, generating hydrogen peroxide and caused bacterial cell death (Hamouda et al. 1999). All in all,  silver nanoparticles isolated from fruits and vegetables peels are good antibacterial agent.

Acknowledgement

Authors are thankful to the Department of Biotechnology, MIET, Meerut for providing infrastructure and financial support for the  project.

Reference

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