Rationale on the High Radical Scavenging Capacity of Betalains

• Main Authors: Karina K. Nakashima (Author), Erick L. Bastos (Author)
• Format: Book
• Published: MDPI AG, 2019-07-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 2076-3921; 10.3390/antiox8070222
• Keywords: betalain; antioxidant; radical scavenger; natural pigments; redox mediator; Therapeutics. Pharmacology; RM1-950
• Source: Antioxidants, Vol 8, Iss 7, p 222 (2019)

Betalains are water-soluble natural pigments of increasing importance as antioxidants for pharmaceutical use. Although non-phenolic betalains have lower capacity to scavenge radicals compared to their phenolic analogues, both classes perform well as antioxidants and anti-inflammatory agents <i>in vivo</i>. Here we show that <i>meta</i>-hydroxyphenyl betalain (<i>m</i>-OH-pBeet) and phenylbetalain (pBeet) show higher radical scavenging capacity compared to their <i>N</i>-methyl iminium analogues, in which proton-coupled electron transfer (PCET) from the imine nitrogen atom is precluded. The 1,7-diazaheptamethinium system was found to be essential for the high radical scavenging capacity of betalains and concerted PCET is the most thermodynamically favorable pathway for their one-electron oxidation. The results provide useful insights for the design of nature-derived redox mediators based on the betalain scaffold.