The antioxidant activity, α-glucosidase and acetylcholinesterase inhibition activity, and chemical composition of Paeonia delavayi petal

Abstract Objectives This study aimed to evaluate the functional activity and phytochemical composition in the flower petals of Paeonia delavayi (P. delavayi) in different colors. Materials and Methods P. delavayi petal extracts were prepared by maceration in methanol, including purple petal extract (PPE), red petal extract (RPE), and yellow petal extract (YPE), and their antioxidant activity and α-glucosidase and acetylcholinesterase inhibition activities were evaluated. To correlate these measured activities to phytochemicals in the petals, an ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS)-based metabolomics method was applied to profile the compositions in the petals of different colors. Finally, the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways database was used to identify the related metabolic pathways that are responsible for the production of these polyphenolic phytochemicals in the petals. Results The results showed that PPE had the highest total phenolic content, total flavonoid content, and the strongest 2,2ʹ-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging ability, ferric reducing antioxidant power, and acetylcholinesterase inhibition ability in all three samples, while YPE showed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and α-glucosidase inhibition ability. A total of 232 metabolites were detected in the metabolomic analysis, 198 of which were flavonoids, chalcones, flavonols, and anthocyanins. Correlation analysis indicated that peonidin-3-O-arabinoside and cyanidin-3-O-arabinoside were the major contributors to the antioxidant activity. Principal component analysis showed a clear separation among these three petals. In addition, a total of 38, 98, and 96 differential metabolites were identified in PPE, RPE, and YPE, respectively. Pathway enrichment revealed 6 KEGG pathways that displayed significant enrichment differences, of which the anthocyanin biosynthesis, flavone and flavonol biosynthesis were the most enriched signaling pathways, revealing a potential reason for the differences in metabolic and functional levels among different colors of P. delavayi petal. Conclusions P. delavayi petals in different colors have different metabolite contents and functional activities, of which the anthocyanin, flavone, and flavonol metabolites are critical in its functional activities, suggesting the anthocyanin biosynthesis, flavone and flavonol biosynthesis pathways are the key pathways responsible for both petal color and bioactive phytochemicals in P. delavayi flowers.