Alcohol has been demonstrated to disrupt intestinal barrier integrity. Some flavonoid compounds that exert antioxidant activity have a protective effect on intestinal barrier function. As an important medicinal and edible plant, sea buckthorn (Hippophae) seeds are rich in flavonoids, but their protective effect on the intestinal barrier has not been reported. In our research, 76 kinds of flavonoids were identified in Hippophae rhamnoides ssp. sinensis seed residue flavonoids (HRSF) by ultra-performance liquid chromatography–tandem mass spectrometry. Kaempferol-3-O-rutinoside, isorhamnetin-3-O-rutinoside, kaempferol-3-O-robinoside-7-O-rhamnoside, isorhamnetin-3-O-2G-rhamnosylrutinoside, quercetin-3-O-rutinoside, (−)-epigallocatechin, and B type of procyanidin were the most abundant substances, accounting for 15.276%, 15.128%, 18.328%, 10.904%, 4.596%, 5.082%, and 10.079% of all identified flavonoids, respectively. Meanwhile, pre-treatment with HRSF was able to prevent alcohol-induced disruption of intestinal barrier integrity through elevating the transepithelial monolayer resistance value, inhibiting the flux of fluorescein isothiocyanate-dextran, and upregulating the mRNA and protein level of TJs (occludin and ZO-1). Furthermore, it was also able to reverse alcohol-induced oxidative stress through suppressing the accumulation of reactive oxygen species and malondialdehyde, improving the glutathione level and superoxide dismutase activity. Finally, the results showed that HRSF pre-treatment effectively elevated the erythroid-related factor 2 mRNA and protein level compared with the alcohol-alone treatment group. Our research was the first to demonstrate that HRSF could prevent alcohol-induced intestinal barrier dysfunction through regulating the Nrf2-mediated pathway in order to attenuate oxidative stress and enhance TJ expression.

The Qinghai–Tibet Plateau is the main production area of Hippophae rhamnoides ssp. sinensis (Rha) and H. tibetana (Tib), but studies on the types and contents of soluble sugars, organic acids, free phenolics, bound phenolics, vitamin C (V_C), tocopherol (V_E) and carotenoids of the two sea buckthorn berries from this region have not been reported. In this paper, we found that the soluble sugars in Rha and Tib were mainly glucose and fructose; Rha exhibited a higher content of total sugar and fructose compared to Tib. The organic acids were mainly quinic acid and malic acid; Rha exhibited a higher content of total acids and quinic acid, but lower tartaric acid and citric acid compared to Tib. Rha also possessed a higher total (free and bound) phenolic as well as total (free and bound) flavonoid content than those in Tib; twelve phenolic compounds were analyzed, among which flavonols were dominant. Catechin, isorhamnetin and quercetin were the main phenolic substances. V_C and V_E (γ-tocopherol (γ-V_E) and δ-tocopherol (δ-V_E)) were higher in Rha than Tib. The total carotenoid, lutein, β-carotene and lycopene content of Tib was remarkably higher than that in Rha. Moreover, both Rha and Tib showed good in vitro and cellular antioxidant activities, and Rha had a stronger antioxidant activity. Taken together, Rha had a higher antioxidant activity, which may be due to its higher content of phenolics, flavonoids, V_C and V_E.

Oxidative stress is known to disrupt intestinal barrier integrity, whereas certain polysaccharides have demonstrated protective effects on intestinal function. This study aimed to isolate a polysaccharide from processed Hippophae rhamnoides subsp. sinensis pomace (remaining after oil and juice extraction) and evaluate its protective effect against H₂O₂-induced intestinal barrier dysfunction in Caco-2 cell monolayers. A polysaccharide fraction, designated SPP-0.2b, with a weight-average molecular weight (Mw) of 42.405 kDa, was successfully isolated by hot water extraction and purified using DEAE-52 cellulose and Sephadex G-100 gel chromatography. Monosaccharide composition analysis revealed that SPP-0.2b was mainly composed of rhamnose, arabinose, galactose, mannose, and galacturonic acid. Compared with the H₂O₂-treated group, SPP-0.2b (500 μg/mL) increased the transepithelial electrical resistance (TEER) by 76.67% and reduced basolateral FITC-dextran fluorescence intensity by 34.63% in Caco-2 monolayers. In addition, SPP-0.2b significantly increased the protein expression levels of Occludin and Zonula Occludens-1 by 79.49% and 66.75%, respectively. SPP-0.2b also reduced intracellular reactive oxygen species and malondialdehyde levels while enhancing the activities of superoxide dismutase and glutathione peroxidase. Collectively, these findings suggest that the protective effect of SPP-0.2b against H₂O₂-induced intestinal barrier dysfunction is associated with the maintenance of tight junction proteins and attenuation of oxidative stress. This study provides experimental evidence supporting the further investigation of SPP-0.2b as a potential functional food ingredient for intestinal health.