Summary
DA‐P, fraction of peptides with a molecular weight <1 kDa isolated from Dendrobium aphyllum, was analysed in three types of cell lines to verify its bioactivity and absorptivity. The cellular antioxidant activity of DA‐P in HepG2 cells was used and results revealed an EC50 of 2.88 ± 0.143 mg mL−1 and a CAA unit of 63.46 ± 2.11 μm QE/100 g peptides. DA‐P treatment enhanced the secretion of cytokines in RAW 264.7 cells. After demonstrating the presence of tight junctions in Caco‐2 monolayers, the absorption was 25.57% ± 0.016% and 19.7% ± 0.012% from different sides. The relatively high absorption indicated that the antioxidant‐relevant immune functions of DA‐P had a greater possibility to be absorbed by Caco‐2 cells. Free amino acids and LC‐MS/MS analysis indicated the degradation and expulsion of components after the absorption of DA‐P, and Ser‐Ser‐Arg was able to come across the monolayers.
Two kinds of flavone extracts were extracted and purified from Labisia pumila (LP). High-performance liquid chromatography (HPLC) analysis was used to determinate the flavones in the extracts, and catechin, glycitin, rutin, naringin, and myricetin were identified in the LP leaf extract (LPL-F) while genistin, naringin, and myricetin were found in the stem extract (LPS-F). Specific flavonol compounds mediated the satisfactory scavenging abilities. The flavone leaf extracts performed better than the stem extracts in chemical antioxidative activities but worse in cellular antioxidative capabilities. The chemical and cellular antioxidative activities were not obviously changed by gastrointestinal digestion but slightly changed at the last 2 hours of intestinal digestion because prolonged exposure to alkaline conditions could destroy the structure of flavonoids. Changes in MDA and GSH content, and enzyme activities of SOD and GSHPx in human erythrocytes during GI digestion indicated the possible intracellular antioxidant-detoxifying mechanisms were through attenuating AAPH-induced oxidative stress by inhibiting ROS generation, in which stem extracts performed the better.
Summary
The structures of two extracts of flavone , obtained from the stem (L40) and leaf (S40) of Labisia pumila (LP), were identified through UHPLC‐MS/MS analysis. An 2,2′‐azobis[2‐methylpropionamidine] dihydrochloride (AAPH)‐induced hemolysis model was used and the results indicate the protective effects of flavone extracts on erythrocytes against AAPH‐induced oxidative stress, in which L40 treatment performed the better. Quantitative analysis of variations in antioxidative‐associated enzyme and non‐enzyme systems within the erythrocytes were conducted and led to the identification of protective pathways in which flavone extracts could pass through the cell membrane and act as AAPH‐free radical scavengers. Absorptivity of flavone extracts was characterised using a Caco‐2 monolayer model, in which the apparent permeability coefficient indicated that both types of flavone extracts were readily absorbed compounds, while L40 showed better intestinal absorptivity. Therefore, we conclude that flavonoid extracts from the leaf of LP show remarkable potential functional effects on human health.
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