Characterization of Polyphenolic Compounds and Antioxidant Activities of Tagetes Flowers With Varying Treatments Using LC-ESI-QToF-MS/MS

Abstract

Tagetes erecta is a valuable medicinal plant, with its flowers being edible and recognized for numerous health benefits attributed to its bioactive polyphenolic compounds. Despite the increasing interest in polyphenols from medicinal plants, limited studies have explored the impact of processing and extraction methods on the bioactive compounds of Tagetes flowers, especially those often discarded after a single use. This study investigated and compared the efficacy of extraction methods on polyphenolic compounds by varying methods of drying and extraction. The total phenolics and their antioxidant activities were measured using free radical scavenging, reducing power, and ferrous ion-chelating assays. LC-ESI-QTOF-MS/MS and high-performance liquid chromatography (HPLC) coupled with a diode array detector (DAD) were used for the identification and quantification of individual phenolic compounds. The higher total phenolic content and flavonoid content were observed in freeze-dried samples of marigold upon ultrasound extraction using ethanol (74.57 mg GAE/g). Antioxidant potential in various assays: DPPH (18.49 mg AAE/g), ABTS (32.14 mg AAE/g), RPA (66.39 mg TE/g), TAC (70.25 mg AAE/g) were also observed highest (70% ethanol), while FRAP (59.76 mg AAE/g), FICA (2.17 mg EE/g), and OH⁻ (267 mg TE/g) in (70% acetone) ultrasonicated extracts of freeze-dried samples. FT-IR of various freeze-dried (FD) extract samples were compared with the raw powder of Tagetes, which exhibited similar functional groups, confirming that ultrasonication had no adverse effect on the functional bioactive compounds. Liquid chromatography with mass spectrometry (LCMS/MS) analysis tentatively identified 33 polyphenolic compounds, including phenolic acids (13), carotenoids (3), flavonoids (14), and other polyphenols in conventional and ultrasound extract samples. High-performance liquid chromatography (HPLC-DAD) quantification of freeze-dried samples showed phenolic acids to be higher for samples [MFEU (85.28 mg/g) > MFAU (70.71 mg/g)] extracted through ultrasound-assisted extraction. These findings indicate that the application of ultrasound-assisted extraction (UAE), in combination with suitable drying methods and solvent systems, can substantially enhance the recovery of functional compounds from Tagetes flowers, its potential utilization in nutraceuticals and functional food products, while also contributing to the reduction of plant-based waste.