Chemical Properties
DPPH is a common abbreviation for the organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable free radical molecules. DPPH has two major applications, both in laboratory research: one is a monitor of chemical reactions involving radicals, most notably it is a common antioxidant assay, and another is a standard of the position and intensity of electron paramagnetic resonance signals.
Physical properties
DPPH has several crystalline forms which differ by the lattice symmetry and melting point. The commercial powder is a mixture of phases which melts at ~130 °C. DPPH-I (m.p. 106 °C) is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is triclinic.
Uses
2,2-Diphenyl-1-picrylhydrazyl is used as a sensitive colorimetric free radical scavenger. It serves as a general antioxidant detector. It is utilized to monitor chemical reactions involving radicals as well as a standard of the position and intensity of electron paramagnetic resonance signals. Further, it is employed in the quantitative determination of aliphatic and aromatic thiols by indirect spectroscopy and for photometric determination of tocopherol.
General Description
2,2-diphenyl-1-picrylhydrazyl is a free radical, which shows hydrogen acceptor ability towards antioxidants. It has a strong absorbance at 517 nm. When the radical is lost in exchange for a proton, the absorbance at 517 nm decreases proportionately, resulting in a color change from purple to yellow. Hence, it is commonly used in DPPH assay for measuring the antioxidant activity of different natural samples such as wine, fruits, herbal tea etc.
Safety
This picrylhydrazyl derivative, also known as DPPH free radical, presents as a black crystalline powder. Store in a refrigerator - this substance is heat sensitive. 1,1-Diphenyl-2-picrylhydrazyl Free Radical is incompatible with oxidizing agents, strong bases and halogens. This chemical is harmful if swallowed. It may cause allergy or asthma symptoms or breathing difficulties if inhaled and an allergic reaction on the skin.
References
[1] SIDDARTHA BALIYAN. Determination of Antioxidants by DPPH Radical Scavenging Activity and Quantitative Phytochemical Analysis of Ficus religiosa.[J]. Molecules, 2022. DOI:
10.3390/molecules27041326.
[2] G. CLARKE. High Correlation of 2,2-diphenyl-1-picrylhydrazyl (DPPH) Radical Scavenging, Ferric Reducing Activity Potential and Total Phenolics Content Indicates Redundancy in Use of All Three Assays to Screen for Antioxidant Activity of Extracts of Plants from the Malaysian Rainforest[C]//2 1. 2013: 1-10. DOI:
10.3390/antiox2010001.
[3] IKUO NAKANISHI Yoshimi S. Electrochemical redox behavior of 2,2-diphenyl-1-picrylhydrazyl radical solubilized by β-cyclodextrin in water[J]. Electrochemistry Communications, 2022, 134: Article 107190. DOI:
10.1016/j.elecom.2021.107190.
[4] JAMES BYH BEHRENDORFF. 2,2-Diphenyl-1-picrylhydrazyl as a screening tool for recombinant monoterpene biosynthesis.[J]. Microbial Cell Factories, 2013, 12: 76. DOI:
10.1186/1475-2859-12-76.
[5] J. XIE K. M S. Re-evaluation of the 2,2-Diphenyl-1-picrylhydrazyl Free Radical (DPPH) Assay for Antioxidant Activity[J]. Journal of Agricultural and Food Chemistry, 2014, 62 19: 4251-4260. DOI:
10.1021/jf500180u.
