Acteoside and salidroside are major phenylethanoid glycosides (PhGs) in Osmanthus fragrans Lour. flowers with extensive pharmacological activities and poor oral bioavailability. The absorption mechanisms of these two compounds remain unclear. This study aimed to investigate the bioaccessibility of these compounds using an in vitro gastrointestinal digestion model and to examine the absorption and transport mechanisms of PhGs using the Caco-2 cell model. The in vitro digestion model revealed that the bioaccessibility of salidroside (98.7 ± 1.35%) was higher than that of acteoside (50.1 ± 3.04%), and the superior bioaccessibility of salidroside can be attributed to its stability. The absorption percentages of total phenylethanoid glycoside, salidroside, and acteoside were 1.42-1.54%, 2.10-2.68%, and 0.461-0.698% in the Caco-2 model, respectively. Salidroside permeated Caco-2 cell monolayers through passive diffusion. At the concentration of 200 μg/mL, the apparent permeability ( P) of salidroside in the basolateral (BL)-to-apical (AP) direction was 23.7 ± 1.33 × 10 cm/s, which was 1.09-fold of that in the AP-to-BL direction (21.7 ± 1.38 × 10 cm/s). Acteoside was poorly absorbed with low P (AP to BL) (4.75 ± 0.251 × 10 cm/s), and its permeation mechanism was passive diffusion with active efflux mediated by P-glycoprotein (P-gp). This study clarified the bioaccessibility, absorption, and transport mechanisms of PhGs. It also demonstrated that the low bioavailability of acteoside might be attributed to its poor bioaccessibility, low absorption, and P-gp efflux transporter.

Phytosterols are well-known for their cholesterol-lowering effects, and the structures and forms of phytosterols affect their bioactivity. We aimed to illustrate the phytosterol profiles in common foods and estimate their natural intake in five geographical regions and among different age groups in China. In total, 12 phytosterols in free and esterified forms of 119 foods from five regions across China were examined using gas chromatography-mass spectrometry. Then, the dietary intake of phytosterols was calculated combined with the dietary foods intake data of Chinese people. The total phytosterol content was highest in vegetable oils (150.4-1230.9 mg/100 g), followed by legumes (129.6-275.6 mg/100 g), nuts (18.9-255.2 mg/100 g), and cereals (11.9-93.8 mg/100 g). Vegetables and fruits contained lower contents of total phytosterols. Phytosterols were mainly esterified in most common foods except in nuts. The predominant phytosterols were β-sitosterol, campesterol, and stigmasterol, all of which belonged to plant sterols and 4-desmethylsterols. Total phytosterol intake varied across different regions, ranging between 257.7 and 473.7 mg/standard-person (sp)/day, with the highest intake in Beijing, followed by Hangzhou, Wuhan, Chongqing, and Guangzhou. However, phytosterol proportion was similar across regions, with β-sitosterol accounting for 46.5-50.3% of the natural intake. Phytosterol intake was mainly constituted by plant sterols and 4-desmethylsterols in esterified form (61.9-74.6%). At the age of 2-70 years, phytosterol intake ranged from 154.3 mg/day to 348.0 mg/day in the national scale.

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Various phytochemicals have been reported to protect against oxidative stress. However, the mechanism underlying has not been systematically evaluated, which limited their application in disease treatment. Nuclear factor erythroid 2−related factor 2 (Nrf2), a central transcription factor in oxidative stress response related to numerous diseases, is activated after dissociating from the cytoskeleton−anchored Kelch−like ECH−associated protein 1 (Keap1). The Keap1-Nrf2 protein-protein interaction has become an important drug target. This study was designed to clarify whether antioxidantive phytochemicals inhibit the Keap1-Nrf2 protein-protein interaction and activate the Nrf2-ARE signaling pathway efficiently. Molecular docking and 3D−QSAR were applied to evaluate the interaction effects between 178 antioxidant phytochemicals and the Nrf2 binding site in Keap1.The Nrf2 activation effect was tested on a H 2 O 2 −induced oxidative−injured cell model. Results showed that the 178 phytochemicals could be divided into high−, medium−, and low−total−score groups depending on their binding affinity with Keap1, and the high−total−score group consisted of 24 compounds with abundant oxygen or glycosides. Meanwhile, these compounds could bind with key amino acids in the structure of the Keap1−Nrf2 interface. Compounds from high−total−score group show effective activation effects on Nrf2. In conclusion, phytochemicals showed high binding affinity with Keap1 are promising new Nrf2 activators.

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