Optimum polyphenol and triterpene contents of Hedera helix (L.) and Scrophularia nodosa (L.): The role of powder particle size

The total polyphenolic and flavonoid contents, as well as the antioxidant free radical scavenging activity (DPPH test) of different sieved powders of Hedera helix (L.) and Scrophularia nodosa (L.), were assessed. Polyphenolic compound content varied significantly between different particle sizes (20-50; 50-100; 100-180; 180-315; > 500 μm). The intermediate classes (between 100 μm and 315 μm) exhibited the highest total polyphenol content with 28.3 mg gallic acid eq./g dry matter (DM), total flavonoid content (8.6 mg catechin eq./g DM) and antioxidant activity (23.5 Trolox eq. mg/g DM). The lowest values were observed for the unsieved powder of Hedera helix (L.), and > 500 μm classes of Scrophularia nodosa (L.). Liquid chromatography coupled with UV detector and mass spectrometry (LC-PDA-ESI/MS) allowed identifying and quantifying polyphenols, flavonoids, iridoids, and triterpene saponins. These latter were exclusively identified by mass spectrometry; unusable signals being recorded by UV measurements. Results showed that most of the compounds presented maximal concentrations in intermediate particle sizes (100 μm-315 μm).