Synthesis, characterization, antioxidant and antimicrobial activity of silver nanoparticles from ethnomedicinal yellow mangosteen leaf extract
摘要
In this study, antimicrobial and antioxidant activities of silver nanoparticles (AgNPs) synthesised from methanolic leaf extract of Garcinia xanthochymus (GX) were evaluated. Optimum parameters for bio-genic synthesis includes 4 mM AgNO3, 4:1 ratio of AgNO3 to G. xanthochymus leaf extract, pH 9, and incubation time of 4 h. Green synthesised AgNPs were characterised using UV–vis absorption spectroscopy, fourier transform infra-red (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and dynamic light scattering (DLS) particle size. The shapes of extract-mediated AgNPs were mainly spherical, with an average size range of 34.27, 24.83 and 37.57 nm in SEM, TEM and DLS analysis, respectively. FTIR measurements indicated peaks corresponding to different functional groups such as hydroxyl groups, carboxylic and aromatic groups, etc., which were involved in the synthesis and stabilisation of AgNPs. Due to bioactive compounds on their surface, green synthesised silver nanoparticles exhibit potent antioxidant and antimicrobial properties. Important bioactive compounds were analysed through GC–MS. The antimicrobial activity of synthesised nanoparticles was assessed against Pseudomonas aeruginosa, Staphylococcus aureus, Aspergillus niger, and Candida albicans. The antioxidant power of synthesised AgNPs was estimated using free radical scavenging activity by (1, 1-Diphenyl-2- picrylhydrazyl) DPPH method. Silver nanoparticles have strong antibacterial activity with a zone of inhibition of 20 mm against S. aureus and antifungal activity with higher zone of inhibition against C. albicans (21 mm). The antioxidant activity of biosynthesized AgNPs increased from 19.3% to 76% with an increase in GX-AgNP concentration. The results confirm that GX-AgNPs have effective antimicrobial and antioxidant activity and enlighten the importance of green synthesised AgNPs. This is the first attempt on evaluation of antimicrobial as well as antioxidant activity of silver nanoparticles from G. xanthochymus methanolic leaf extract.