Versatile oligomers and polymers from flavonoids – a new approach to synthesis

Abstract

Catechin, a flavanol, and quercetin, a flavonol, are two flavonoids that have demonstrated a number of potential health effects, including antioxidant, anti-inflammatory, anti-cancer, antihypertensive and antimicrobial effects. In this article, we describe a new facile procedure for preparing oligomers and polymers from catechin and quercetin, utilising only solvent and hydrochloric acid, which can be tuned to yield water soluble catechin oligomers (polycat) up to 3300 g mol⁻¹, water soluble quercetin oligomers (polyqcn) of 3100 g mol⁻¹ and higher molecular weight catechin polymers up to 15 000 g mol⁻¹. The polymers were characterised by size exclusion chromatography (SEC), UV-Vis spectroscopy and ¹H, ¹H–¹³C HSQC and ¹H–¹³C HMBC NMR spectroscopy. Evidence is presented for the polymerisation to occur through a step-growth mechanism. All polymers exhibited considerable free-radical scavenging capacity, indicating their potential for various therapeutic applications ranging from drug delivery for the lower molecular weight water soluble oligomers to tissue engineering, anti-oxidant coatings and eco-friendly material engineering applications for the higher molecular weight water insoluble polymers.