Variation in polyphenolic profile and in vitro antioxidant activity of eastern teaberry (Gaultheria procumbens L.) leaves following foliar development

Abstract

Seasonal dynamics in the polyphenolic composition, antioxidant activity, and their relationships during plant development were evaluated for eastern teaberry (Gaultheria procumbens L.) leaves, a traditional herbal medicine of North American natives. With the complementary UHPLC-PDA-ESI-MS3, HPLC-PDA-fingerprint, Folin-Ciocalteau, and n-butanol/HCl assays of methanol-water (75:25, v/v) extracts, the dried leaf samples harvested monthly across the growing season under Polish climate conditions were found rich in structurally diverse polyphenols (149.2–210.7mg/g DW) including the dominating salicylates (64.6–107.5mg/g DW), proanthocyanidins (53.0–66.8mg/g DW), and flavonoids (17.3–25.3mg/g DW), and the accompanying chlorogenic acid isomers (2.4–4.4mg/g DW) and simple phenolic acids (0.9–1.1mg/g DW). Among 28 detected analytes, gaultherin (64.6–107.5mg/g DW), miquelianin (14.6–21.1mg/g DW), procyanidin A-type trimer (5.5–9.5mg/g DW), and (–)-epicatechin (5.8–7.8mg/g DW) were the most abundant. The phenolic levels and antioxidant activity parameters in the DPPH (EC50, 15.0–18.2μg DW/mL; 0.95–1.16mmol Trolox equivalents/g DW) and FRAP (2.3–3.4mmolFe 2+/g DW; 0.86–1.26mmol Trolox equivalents/g DW) assays showed parallel seasonal trends with maxima in September and October. As the subsequent correlation studies confirmed the determinative impact of polyphenols on the leaf antioxidant activity and its seasonal fluctuations, the Fall season could be recommended as optimal for harvesting the plant material for medicinal purposes and cost-effective production of natural health products.