Effects of Growing Location and Harvest Time on the Phytochemical Composition and Bioactivities of Firmiana simplex Leaves.

Abstract

Firmiana simplex leaves are traditionally used in Chinese medicine for dispelling wind-dampness, detoxifying, and lowering blood pressure, yet their chemical basis remains unclear. This study investigated how growing location (waterside, riverside, riverside field) and harvest time (June, July) affect the leaf's chemical composition and bioactivities using optimized 70% ethanol extraction. Leaves from riverside field harvested in July (S3) exhibited the highest total polyphenols (10.74 mg/g), polysaccharides (52.54 mg/g), and protein (5.23 mg/g), as well as strong antioxidant activity and moderate α-glucosidase inhibitory activity (half-maximal inhibitory concentrations, IC50 = 0.21 g/mL). Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) identified 122 compounds, including 42 flavonoids, 25 organic acids, and 13 terpenoids. Three compounds (two glycosides and one flavonoid) are tentatively assigned as potential new natural products based on the MS/MS spectral matching. Key compounds such as quercetin, rutin, chlorogenic acid, and ursolic acid have been documented to exert anti-inflammatory, antihypertensive, and detoxifying effects, suggesting potential correlations with the traditional medicinal applications of this plant. The July harvest from riverside fields represents the best-performing condition among the growing locations and harvest times evaluated in the present study, providing a scientific basis for its ethnopharmacological use.

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