TRITERPENOID SAPONINS: A REVIEW ON BIOSYNTHESIS, APPLICATIONS AND MECHANISM OF THEIR ACTION

Saponins are the potential bioactive compounds secreted by plants, endophytic fungi and marine organisms. Saponins are the glycosides containing non sugar portion, aglycone (sapogenin) attached to sugar moiety by glycosidic linkage. Depending on the chemical nature of aglycone, saponins are of triterpenoid and steroid saponins. The present review gives an overview of the biosynthesis pathway of triterpenoid saponins and mechanism of the biosynthesis. The review discusses the biomedical and pharmaceutical importance of triterpenoid saponins as they possess different activities including antimicrobial, haemolytic, hypolipidemic, immunomodulating and cytotoxic activities. The review also focuses on the mechanism of their action towards various activities.Â

RAPID SYNTHESIS OF SILVER NANOPARTICLES USING AQUEOUS LEAF EXTRACT OF ACHYRANTHES ASPERA AND STUDY OF THEIR ANTIMICROBIAL AND FREE RADICAL SCAVENGING ACTIVITIES

Objective: To study the biosynthesis of silver nanoparticles (AgNPs) using the aqueous leaf extract of Achyranthes aspera and check the antimicrobial and free radical scavenging activity of the biosynthesized AgNPsMethods: 20 ml of aqueous leaf extract of A. aspera was added to 80 ml of 2 mM silver nitrate and the reaction solution was heated at 55-60 °C for 20 min and incubated. Biosynthesized AgNPs were characterized by different spectroscopic measurements including UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction pattern (XRD), Transmission electron microscopy (TEM) and Dynamic light scattering (DLS). Antimicrobial activity of AgNPs was checked against Staphylococcus aureus, Bacillus subtilis (Gram+ve bacteria), Klebsiella pneumonia, Pseudomonas aeruginosa (Gram-ve bacteria), Aspergillus niger, Candida albicans and Candida nonalbicans (Human pathogenic fungi) by employing disc diffusion method. The free radical scavenging activity of AgNPs was checked against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Hydrogen peroxide (H2O2) radicals. Results: After 1 h of incubation, the light yellow color of the reaction solution was turned to dark brown. UV-Vis spectra showed the absorption peak at 445 nm and confirmed the synthesis of AgNPs. FTIR spectra revealed the functional groups plausibly involved in the biosynthesis and stabilization of AgNPs. XRD pattern revealed that the synthesized AgNPs were crystalline in nature with face-centered cubic (FCC) phase. TEM revealed that the synthesized AgNPs were spherical in shape with 20-40 nm in size. DLS analysis revealed that the average size of AgNPs was 24.5 nm. Biosynthesized AgNPs were highly stable due to their high negative zeta potential value of-28.1 mV. AgNPs showed effective antimicrobial activity against S. aureus (16.4 mm), B. subtilis (14.5 mm), K. pneumonia (13.2 mm), P. aeruginosa (12.4 mm), A. niger (12.2 mm), C. albicans (11.5 mm) and C. nonalbicans (11.8 mm). AgNPs showed effective free radical scavenging activity with IC50 values of 77.73 and 90.53 µg/ml respectively against DPPH and H2O2 radicals.Conclusion: Successful and rapid synthesis of AgNPs was achieved using aqueous leaf extract of A. aspera. Biosynthesized AgNPs were proved to be excellent antimicrobial agents and free radical scavengers.Keywords: Achyranthes aspera, Silver nanoparticles, TEM, DLS, Antimicrobial and Radical scavenging activit

BIOFABRICATION OF SILVER NANOPARTICLES USING AQUEOUS LEAF EXTRACT OF MELIA DUBIA, CHARACTERIZATION AND ANTIFUNGAL ACTIVITY

Objective: To investigate the bio-fabrication of silver nanoparticles (AgNPs) using aqueous leaf extract of Melia dubia (ALM) and test the antifungal activity of AgNPs against pathogenic fungi Aspergillus niger and Candida tropicalis. Methods: 10 ml of aqueous leaf extract of Melia dubia was added to 90 ml of 1 mM silver nitrate and incubated for 8h at room temperature. After incubation, the color change was observed from light yellow to dark brown. The synthesized AgNPs were characterized using UV-Vis spectroscopy, Fourier Transform Infra red spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron microscopy (SEM), X-ray diffraction analysis (XRD) and Atomic Force Microscopy (AFM). Antifungal activity against Aspergillus niger and Candida tropicalis was carried out by employing the disc diffusion method. Results: UV-Vis spectra confirmed the synthesis of AgNPs by showing characteristic peak between 380-450 nm*. FTIR spectra showed the functional groups possibly involved in the synthesis of AgNPs. EDX confirms the presence of elemental silver at 3 Kev. SEM and AFM showed the synthesized AgNPs were spherical in shape with size ranging between 20-40 nm*. XRD analysis revealed the crystalline nature of AgNPs with face centred cubic (FCC) lattice. AgNPs was found to be very effective against the tested pathogenic fungi A. niger and C. tropicalis and formed the inhibition zones 13.0 and 14.5 mm respectively. Conclusion: It is concluded that the bio-fabrication of AgNPs using aqueous leaf extract of Melia dubia was robust and rapid. The AgNPs were stable and proved to be excellent antifungal agents

ENDOPHYTIC FUNGAL ASSISTED SYNTHESIS OF SILVER NANOPARTICLES, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY

Objective: The objective was to investigate the biosynthesis of silver nanoparticles (SNPs) using extracellular fungal filtrate of Aspergillus niger andcheck their antimicrobial activity against Staphylococcus aureus and Escherichia coli.Methods: 10 ml of extracellular fungal filtrate of A. niger was added to 50 ml of 1 mM silver nitrate and incubated at room temperature for 24 hrs.SNPs were characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transforms infrared spectroscopy (FTIR), transmission electronmicroscopy (TEM), atomic force microscopy (AFM), and X-ray diffraction analysis (XRD). Antimicrobial activity was checked against S. aureus andE. coli by employing disc diffusion method.Results: The color change of the solution from light yellow to dark brown indicated the formation of SNPs. The formation of SNPs was furtherconfirmed by UV-Vis spectroscopy, which showed the characteristic peak between 400 and 460 nm. TEM and AFM analysis showed that the size ofSNPs were between 10 and 50 nm with roughly spherical in shape. XRD analysis confirmed the crystalline nature of SNPs synthesized by showing theBraggs peaks which could be indexed to (111) and (220) of face cubic crystal phase of silver. FTIR showed the peaks at 1026, 1215, 1348, 1632, and2928/cm, which were responsible for the different functional groups possibly involved in the synthesis and stabilization of SNPs. The SNPs formedthe inhibition zones of 14.0 and 12.5 mm against S. aureus and E. coli, respectively.Conclusion: It is concluded that the biosynthesis of SNPs using extracellular fungal filtrate of A. niger was simple, eco-friendly, and robust. The SNPssynthesized were well-dispersed, crystalline in nature and also proved to be excellent antimicrobial agents.Keywords: Silver nanoparticles, Aspergillus niger, Transmission electron microscopy, X-ray diffraction, Antimicrobial activity