Flavonoid and Lignan Glycosides from the Leaves of Melia Azedarach

Diverse Structures of Tea Polyphenols from Rougui Wuyi Rock Tea and Their Potential as Inhibitor of 3C-like Protease

Tea polyphenols, the primary bioactive constituents responsible for the various health benefits of tea, can be categorized into different subgroups according to their structural characteristics. However, the distinctions in antiviral activity among the diverse types of polyphenolic compounds remain unexplored. In the present study, fifty-eight tea polyphenols with varied structures, including eleven undescribed compounds, were isolated from Rougui Wuyi rock tea. Their molecular structures were elucidated using comprehensive analytical approaches of NMR, HRMS, CD spectroscopic data and acid hydrolysis. The isolated polyphenol analogs could be structurally classified into two main categories: flavan-3-ols, which include catechins, flavoalkaloids, procyanidins and theasinensins, and flavones, encompassing kaempferol, quercetin, myricetin, and their respective glycosides. The inhibitory activities of fifty-eight tea polyphenols against 3CLpro were assessed in vitro, and eighteen phenolic compounds exhibited inhibitory effects on 3CLpro, with IC50 values ranging from 9.8 μM to 61.1 μM. Among them, two types of tea polyphenols, catechin and flavoalkaloid derivatives, demonstrated superior inhibitory effects compared to other categories. The structure-activity relationship was further explored, and molecular docking analysis revealed that the differing inhibitory effects of catechin and flavoalkaloid derivatives were attributed to the variations in the number and positions of the hydrogen bond interactions with 3CLpro. This study provides a valuable understanding of tea polyphenols and supplies potential lead compounds for antiviral drugs.

Comprehensive Analysis of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. Leaves Based on UPLC-MS/MS: Separation and Rapid Qualitative and Quantitative Analysis

Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves (ESL) have long been people’s favorite as a natural edible green vegetable, in which phenols and saponins are the main characteristic and bioactive components. This study was first carried out to comprehensively analyze the phenols and saponins in ESL, including phytochemical, qualitative, quantitative, and bioactivity analysis. The results showed that 30 compounds, including 20 phenolic compounds and 7 saponins, were identified. Twelve of them were isolated from Eleutherococcus Maxim. for the first time. In the qualitative analysis, 30 phenolic compounds and 28 saponins were accurately detected. Their characteristic cleavage processes were described by UPLC-QTOF-MS/MS. Ten representative ingredients were quantitated in 29 different regions via a 4000 QTRAP triple quadrupole tandem mass spectrometer (UPLC-QTRAP-MS/MS), and it was found that S19 (69.89 ± 1.098 mg/g) and S1 (74.28 ± 0.733 mg/g) had the highest contents of total phenols and saponins, respectively. The newly developed analysis method for the quantitative determination was validated for linearity, precision, and limits of detection and quantification, which could be applied to the quality assessment of ESL. In vitro experiment, the α-glucosidase inhibitory effect of the phenolic fraction was higher than others, indicating that the phenolic content may be related to the hypoglycemic activity. It was also suggested that ESL could be developed as a natural potential effective drug or functional food.