Emphasis Type="Italic"Abroma augusta/Emphasis

Authors: Subhajit Das Braja Gopal Bag Ranadhir Basu

Publish Date: 2014/11/28

Volume: 5, Issue: 7, Pages: 867-873

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Abstract

The bark extract of Abroma augusta Linn is rich in medicinally important phytochemicals including antioxidants and polyphenols First one step green synthesis of gold nanoparticles AuNPs has been described utilizing the bark extract of Abroma augusta L and chloroauric acid under very mild reaction conditions The phytochemicals present in the bark extract acted both as a reducing as well as a stabilizing agent and no additional stabilizing and capping agents were needed Detailed characterizations of the stabilized AuNPs were carried out by surface plasmon resonance spectroscopy high resolution transmission electron microscopy and Xray diffraction studies The catalytic activity of the freshly synthesized gold nanoparticles has been demonstrated for the sodium borohydride reduction of 4nitrophenol to 4aminophenol and the kinetics of the reduction reaction have been studied spectrophotometricallyGold nanoparticles AuNPs with unique optical electronic and magnetic properties have drawn tremendous research interests during the last two decades Alkilany et al 2013 Zhang et al 2012 because of their applications in diversified areas such as catalysis Wittstock and Baumer 2014 Liu et al 2014 drug delivery biodiagnostics Murphy et al 2008 medical imaging Huang et al 2009 plasmonics Pelton et al 2008 and chemical sensing AuNPs dispersed in water and stabilized with nontoxic biomolecules are required for many of such applications Among various methods reported for the synthesis of AuNPs the plant extractmediated reductive method involving the reduction of AuIII to Au0 by the phytochemicals has gained profound significance in recent years due to the renewable and nontoxic nature of the phytochemicals mild reaction conditions ecofriendly aqueous medium etc The method is advantageous over other synthetic methods because the phytochemicals present in the plant extract act both as a reducing agent as well as a stabilizer and no additional stabilizers or capping agents are needed The green synthesis of AuNPs from the extracts of Macrotyloma uniflorum Aromal et al 2012 Trigonella foenumgraecum Aromal and Philip 2012 Aloe vera Chandran et al 2006 Acacia nilotica leaf Majumdar et al 2013 Saraca indica bark Dash et al 2014 Punica granatum Dash and Bag 2014 Green coconut shell Paul et al 2014 etc has been reported Mittal et al 2013 Due to rapid emergence of newer applications of nanoparticles and nanomaterials there is an ever growing need for the development of newer methods for the synthesis of metal nanoparticles utilizing plant resources as renewablesAbroma augusta Linn is a small evergreen plant growing upto 3–4 m in height with velvety branches and found in tropical Asia South and Eastern Africa and Australia Usually found as a wild plant or as an ornamental plant in garden Abroma augusta L belongs to the family of Sterculiaceae and it is also an important Ayurvedic medicinal plant Various parts of the plant have been used for the treatment of diabetes rheumatic pain of joints uterine disorders headache with sinusitis nervous dysmenorrhoea amenorrhoea sterility menstrual disorder etc Gupta et al 2011 During our investigations on the utilization of triterpenoids C30s as renewable functional nanoentities Bag and Dash 2011 Bag and Paul 2012 Bag et al 2012 2013 Bag and Majumdar 2012 2014 it occurred to us that the medicinally important bark extract of Abroma augusta L rich in polyphenolic compounds can be utilized for the synthesis of AuNPs from HAuCl4 Mittal et al 2013 Herein we report the experimental evidence for the presence of antioxidants including polyphenols in the bark extract of Abroma augusta L and the use of the bark extract for a very mild environment friendly and efficient synthesis of AuNPs without any additional capping or stabilizing agents The stabilized colloidal AuNPs were characterized by high resolution transmission electron microscopy HRTEM selected area electron diffraction SAED surface plasmon resonance SPR spectroscopy and Xray diffraction studies Catalytic activity of the freshly synthesized colloidal AuNPs has been demonstrated for the sodium borohydride reduction of 4nitrophenol to 4aminophenol in water at room temperature as a model reaction and the kinetics of the reduction reaction have been investigated spectrophotometricallyThe bark of Abroma augusta L was collected from the local area of Midnapore West Bengal India and identified at the Department of Botany and Forestry Vidyasagar University Midnapore The bark was cut into small pieces dried in air and then powdered using a grinder Finely powdered Abroma augusta bark 20 g was suspended in ethanol 120 mL refluxed for 5 h and filtered Volatiles of the filtrate were removed under reduced pressure to afford a greenish black sticky solid 044 g The crude greenish black sticky solid was dissolved in ethanol 30 mL and filtered through a Celite bed The volatiles of the filtrate were removed under reduced pressure to afford a solid 033 g Purified Abroma augusta bark extract 002 g was suspended in a mixture of distilled water and ethanol 10 mL 41 and sonicated using an ultrasonicator bath for 45 min to obtain a semitransparent solution 2000 mg L−1The most extensively used stable DPPH radical was employed for the study of antioxidant property of bark extract of Abroma augusta Antioxidants present in the extract react with DPPH radical and convert it to 11diphenyl2picrylhydrazine The color change from violet to yellowish within 30 min upon addition of the bark extract to DPPH solution indicated the antioxidant property of the extract The reduction in the absorbance intensity at 517 nm was studied by UV–visible spectrophotometryThe presence of phenolic compounds in the bark extract of Abroma augusta was examined qualitatively by ferric chloride test The extract of the bark of Abroma augusta 1 mL was mixed with an aliquot of freshly prepared concentrated FeCl3 solution and the mixtures was shaken vigorously Appearance of greenish color almost instantly indicated the presence of phenolic compounds in the bark extract

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