Phenolic mapping and associated antioxidant activities through the annual growth cycle of sugar maple leaves

Concentrations of antioxidant components (analyzed by HPLC-UV) and antioxidant attributes (assayed by radical scavenging and non-radical redox potential methods) of sugar maple leaves (SML) from different harvesting times were investigated. Moreover, measurements of colorimetry, SEM, and FTIR spectroscopy-based characterization of leaves composition, throughout the growth cycle, were performed. Results showed that the antioxidant activities of SML are strongly correlated with phenolic contents and significantly (p < 0.05) varied with harvesting time where minimum amount of total phenolics (105.67 & PLUSMN; 13.16 mg GAE/g DM) and total flavonoids (3.27 & PLUSMN; 0.26 mg CTE/g DM) were found to be concentrated in Fall leaves. The absorption bands obtained from FTIR spectra revealed the presence of functional groups that have great significance towards the antioxidant activity of SML. Principal component analysis revealed that biosynthesis of maximum phenolic compounds in SML mostly occurs during the leaf expansion and growth phases. The obtained data provided a better understanding towards the effect of harvesting time on the phenolic mapping of SML in favor of its valorization into functional food ingredients.

Automated summary

Concentrations and attributes of antioxidant components in sugar maple leaves were studied based on HPLC-UV and radical scavenging/redox potential methods respectively. Colorimetry, SEM, and FTIR spectroscopy measurements were conducted to characterize the composition of leaves throughout the growth cycle. The results showed that the antioxidant activities of sugar maple leaves were strongly associated with phenolic contents and varied significantly with harvesting time. The FTIR spectra revealed the presence of functional groups that are important for the antioxidant activity. Principal component analysis indicated that the biosynthesis of phenolic compounds in sugar maple leaves mainly occurs during the leaf expansion and growth phases. These findings provide valuable insight into the effect of harvesting time on the phenolic composition of sugar maple leaves and their potential use as functional food ingredients.