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Subject: Animal Biochemistry × Start date: 2013 × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    GREEN SYNTHESIS & CHARACTERISATION OF SILVER NANOPARTICLES AND ASSESSMENT OF ITS ANTIOXIDANT & ANTIMICROBIAL ACTIVITY
    (College of Veterinary Science, Assam Agricultural University Khanapara, Guwahati-781022, 2017-07) Deka, Naba Jyoti; Nath, Rita
    The present study was undertaken to green synthesis of silver nanoparticles using leaves of Neem (Azadirachta indica) and Tulsi (Ocimum tenuiflorum) and to evaluate their antimicrobial & in-vitro antioxidant activities. The plants Neem (Azadirachta indica) and Black Tulsi (Ocimum tenuiflorum) were procured from different nearby places of Guwahati, Kamrup (metro) district, Assam. The dried leaves were pulverized and methanolic and aqueous extracts were prepared. The preliminary qualitative hytochemical analysis of Neem (Azadirachta indica) and Tulsi (Ocimum tenuiflorum) leaves showed the presence of steroid, phenol, tannin, saponin, flavonoid, alkaloid and triterpenes. The mean ± SE of total phenol of Neem and Tulsi were 0.019 ± 0.001 and 0.022 ±0.002 (mg/ml) respectively with no significant difference (P>0.05) between the two plants. The tannin content of Neem and Tulsi were 0.61 ± 0.010 and 0.580 ± 0.000 (mg/ml), flavonoid content were 0.34 ± 0.010 and 0.240 ± 0.010 (%) alkaloid content were 2.67 ± 0.010 and 2.030 ± 0.020 (%) and saponin content were 0.52 ± 0.01 and 0.410 ± 0.01 (%) respectively. Neem showed a significantly (P<0.05) higher concentration of flavonoid, alkaloid and saponin. Though tannin content was higher in Neem than Tulsi but it was found non-significant (P>0.05). The formation of silver nanoparticles were confirmed by the colour change followed by UV-Vis spectrophotometer analysis. The zeta potential measurement of the nanoparticles using Neem and Tulsi leaf extract were found to be -48.9 mV and -18.4 mV respectively. The synthesized nanoparticle were found to be almost spherical in shape in SEM images in both cases. The synthesized nanoparticles showed sensitive response against both gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia coli) which indicates that it has antimicrobial activity. The antioxidant activity of the methanolic extract, aqueous extract and silver nanoparticles from both Neem and Tulsi were evaluated by using four different standard methods. In DPPH antioxidant assay, the aggregate percent inhibition of aqueous, methanolic and silver nanoparticle of Neem leaf extract was 80.57±0.74, 63.55±0.34 and 85.16±1.44 while that of Tulsi was 68.28±0.59, 67.42±0.26 and 77.12±0.58 respectively. In nitric oxide radical assay ,The percent inhibition of nitric oxide of AgNPs of Neem extract at 50, 80 and 110 ug/ml were 73.29±0.22, 74.32±0.13 and 75.46±0.22 and of Tulsi were 12.61±0.15, 14.67±0.07 and 16.37±0.05 respectively . The aggregate value of super oxide radical scavenging activity of methanolic extract of Neem and Tulsi at different concentration were from 58.04±1.74 and 54.60±1.15 respectively and that of aqueous extract were 72.08±2.04 and 68.98±1.29 respectively .Again, in reductive ability evaluation, both aqueous and methanolic extracts of Neem and Tulsi showed higher reducing power than the standard Butylated hydroxytoluenme .Though silver nanoparticles of both the plants showed reducing power but it was found to be weaker than the standard . It may be concluded that AgNPs derived from Azadirachta indica (Neem) is richer in phytochemicals, antioxidant property and antibacterial activity than AgNPs derived from Ocimum tenuiflorum and can be further exploited for their medicinal and industrial properties.