Antioxidant Activity of Hispidin Oligomers from Medicinal Fungi: A DFT Study
El Hassane Anouar,
Syed Adnan Ali Shah,
Normahanim Binti Hassan,
Najoua El Moussaoui,
Rohaya Ahmad,
Mohd Zulkefeli,
Jean-Frédéric F. Weber
Affiliations
El Hassane Anouar
Atta-ur-Rahman Institute for Natural Products Discovery, Level 9, FF3, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia
Syed Adnan Ali Shah
Atta-ur-Rahman Institute for Natural Products Discovery, Level 9, FF3, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia
Normahanim Binti Hassan
Atta-ur-Rahman Institute for Natural Products Discovery, Level 9, FF3, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia
Najoua El Moussaoui
Department of Biology, Science Faculty, Abdelmalek Essaâdi University, Tetouan, 2121, Morocco
Rohaya Ahmad
Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia
Mohd Zulkefeli
Atta-ur-Rahman Institute for Natural Products Discovery, Level 9, FF3, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia
Jean-Frédéric F. Weber
Atta-ur-Rahman Institute for Natural Products Discovery, Level 9, FF3, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia
Hispidin oligomers are styrylpyrone pigments isolated from the medicinal fungi Inonotus xeranticus and Phellinus linteus. They exhibit diverse biological activities and strong free radical scavenging activity. To rationalize the antioxidant activity of a series of four hispidin oligomers and determine the favored mechanism involved in free radical scavenging, DFT calculations were carried out at the B3P86/6-31+G (d, p) level of theory in gas and solvent. The results showed that bond dissociation enthalpies of OH groups of hispidin oligomers (ArOH) and spin density delocalization of related radicals (ArO•) are the appropriate parameters to clarify the differences between the observed antioxidant activities for the four oligomers. The effect of the number of hydroxyl groups and presence of a catechol moiety conjugated to a double bond on the antioxidant activity were determined. Thermodynamic and kinetic studies showed that the PC-ET mechanism is the main mechanism involved in free radical scavenging. The spin density distribution over phenoxyl radicals allows a better understanding of the hispidin oligomers formation.
