1-1-diphenyl-2-picrylhydrazyl and cadmium-telluride

This study was undertaken to evaluate the antioxidant potential of an aqueous extract from Merremia emarginata leaves because this plant has a very high flavonoid and phenol content. The in vitro antioxidant activity was measured by diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid (ABTS), superoxide anion scavenging assay and lipid peroxidation activity; the total reducing capability of the plant extract indicates that this plant is a source for natural antioxidants. Furthermore, we investigated thio glycolic acid-capped cadmium telluride quantum dots (TGA-CdTe QDs) as fluorescent probes to study the antioxidant activity of the M. emarginata extract through fluorescence quenching. The antimicrobial activity was also investigated using a disc diffusion method and fluorescence microscopy. The TGA-CdTe QDs and M. emarginata complex could provide antimicrobial activity through a reactive oxygen species pathway and/or microbial endocytosis through an electrostatic attraction. Based on our findings, we suggest that the QDs act as potential probes for the in vitro antioxidant and antimicrobial activities. In addition, their cooperative effect with the plant extract indicates that QDs could be used as nanocarriers to enhance the antimicrobial capability. Further in vivo studies on the photolabelling of antioxidants with QDs will provide insights into the mechanistic pathways of secondary metabolites against various degenerative diseases.

Topics: Anti-Bacterial Agents; Antioxidants; Benzothiazoles; Biphenyl Compounds; Cadmium Compounds; Convolvulaceae; Diffusion; Escherichia coli; Flavonoids; Indicators and Reagents; Lipid Peroxidation; Microbial Sensitivity Tests; Nanoparticles; Phenols; Picrates; Plant Extracts; Plant Leaves; Quantum Dots; Spectrometry, Fluorescence; Sulfonic Acids; Superoxides; Tellurium; Thioglycolates

The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH(·) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV-vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH(·) radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH(·) may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH(·) is proposed.

Topics: Biphenyl Compounds; Cadmium Compounds; Fluorescence; Fluorometry; Free Radicals; Kinetics; Picrates; Quantum Dots; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Tellurium