Bioavailability Assessment of Yarrow Phenolic Compounds Using an In Vitro Digestion/Caco-2 Cell Model: Anti-Inflammatory Activity of Basolateral Fraction

Effect of gastrointestinal digestion on the stability, antioxidant activity, and Caco-2 cellular transport of pigmented grain polyphenols

Grain polyphenols are known to possess several health properties. However, their digestive stability and intestinal absorption have not been fully elucidated. This study investigated the fate of pigmented grain polyphenols in the digestive system. Purple rice, purple barley, purple wheat, and blue wheat extracts were subjected to simulated gastric and intestinal phase digestion, followed by Caco-2 cellular transport. Phenolic profiling and antioxidant activity were determined using benchtop assays and an ultra-high-performance liquid chromatography-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid free radical) (UHPLC-ABTS•+) system. The results demonstrated a decrease in the total phenolic content of extracts after digestion, with purple rice extract retaining the highest phenolic content (79%) and ABTS•+antioxidant activity (31%). Antioxidant activity was retained the most during the gastric phase; however, dominant antioxidant compounds were not detected after intestinal digestion. Significant variations in phenolic composition and radical scavenging activity were detected after digestion. Protocatechuic acid, vanillic acid, apigenin, and chrysoeriol were all transported across the intestinal barrier. The findings of this study provide novel insights into the in vitro stability and antioxidant activity of cereal grain polyphenols after simulated digestion.

Hypoglycemic effect and intestinal transport of phenolics-rich extract from digested mulberry leaves in Caco-2/insulin-resistant HepG2 co-culture model

Phenolics of mulberry (Morus alba L.) leaves (MLs) have potential anti-diabetic effects, but they may be chemically modified during gastrointestinal digestion so affect their biological activity. In this study, an in vitro digestion model coupled with Caco-2 monolayer and Caco-2/insulin-resistant HepG2 coculture model were used to study the transport and hypoglycemic effects of phenolics in raw MLs (U-MLs) and solid-fermented MLs (F-MLs). The results of LC-MS/MS analysis showed that the Papp (apparent permeability coefficient, 10-6cm/s) of phenolics in digested MLs ranged from 0.002 ± 0.00 (quercetin 3-O-glucoside) to 60.19 ± 0.67 (ferulic acid), indicating higher phenolic acids absorbability and poor flavonoids absorbability. The Papp values of phenolic extracts of F-MLs in Caco-2 monolayer were significantly higher (p > 0.05) than that of U-MLs. Digested phenolic extracts inhibited the activities of sucrase (60.13 ± 2.03 %) and maltase (82.35 ± 0.78 %) and decreased 9.28 ± 0.84 % of glucose uptake in Caco-2 monolayer. Furthermore, a decrease in the mRNA expression of glucose transporters SGLT1 (0.64 ± 0.18), GLUT2 (0.14 ± 0.02) and the sucrase-isomaltase (0.59 ± 0.00) was observed. In Caco-2/insulin-resistant HepG2 co-culture model, phenolic extracts regulated glucose metabolism by up-regulating the mRNA expressions of IRS1 (9.32-fold), Akt (17.07-fold) and GYS2 (1.5-fold), and down-regulating the GSK-3β (0.22-fold), PEPCK (0.49-fold) and FOXO1 (0.10-fold) mRNA levels. Both U-MLs and F-MLs could improve glucose metabolism, and the partial least squares (PLS) analysis showed that luteoforol and p-coumaric acid were the primary phenolics that strongly correlated with the hypoglycemic ability of MLs. Results suggested that phenolics of MLs can be used as dietary supplements to regulate glucose metabolism.

Gochnatia glutinosa (D.Don) D.Don ex Hook. & Arn.: A plant with medicinal value against inflammatory disorders and infections

Gochnatia glutinosa is a shrub that grown in the Argentinean semiarid region (Monte region) used in the ancestral medicine as an antiseptic and anti-inflammatory agent. This study was aimed to examine the morpho-anatomical characteristics of G. glutinosa aerial parts, identify the chemical composition of traditionally used preparations to assess its pharmacobotanical characterization and evaluate its activity as antiseptic and anti-inflammatory to give scientific support to its traditional uses. G. glutinosa morpho-anatomical description was performed following standard histological techniques. Tincture and infusion of its aerial parts were prepared and were subjected to phytochemical analysis. Xanthine oxidase (XOD) and lipoxygenase (LOX) inhibition experiments, as well as ABTS^•+, superoxide radical, and hydrogen peroxide scavenging activity, were carried out. The growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA) strains was also determined. The morpho-anatomical traits of G. glutinosa leaves and stems were reported for the first time. The medicinal preparations exhibited a large amount of phenolic chemicals mainly flavonoids such as rhamnetin, arcapillin, rhamnacin, hesperetin, isorhamnetin, centaureidin, europetin 7-O-mehylmyricetin, cirsiliol, sakuranetin, genkwanin and eupatorine and also phenolic acids and diterpenoid derivatives. Both preparations had free radical scavenging activity and were able to reduce both XOD and LOX activity, indicating their anti-inflammatory properties. Besides, tincture was effective against all MRSA strains (MIC values ranging from 60 to 240 g DW/mL). The results obtained in this work scientifically support the medicinal popular use of G. glutinosa as an antiseptic and anti-inflammatory. The identification of bioactive compounds and their morpho-anatomical description contribute to the quality control of this medicinal plant from Argentine Calchaquí Valley.

Subcritical Water Extraction as an Effective Technique for the Isolation of Phenolic Compounds of Achillea Species

The genus Achillea has significant medical potential due to the presence of highly bioactive compounds in its chemical composition. To take advantage of plants’ biomedical potential, it is of great importance to use a proper extraction process. This study aimed to determine and compare the preliminary chemical composition of five different Achillea species extracted with two conventional (infusion and maceration) and two non-conventional (ultrasound-assisted extraction (UAE) and Subcritical water extraction (SWE)) techniques. The extracts were prepared using the previously described procedures for infusion, maceration, UAE and SWE extraction. For all extracts, the extraction yield (dry extract (DE)) was determined. The analyzed extracts were preliminarily chemically characterized spectrophotometrically in terms of total phenolic content (TPC) and total flavonoid content (TFC). The obtained results showed that non-conventional techniques delivered higher values of TPC and TFC than conventional. There is a statistically significant increase in DE and TPC content when applying SWE for all observed Achillea species. The highest DE value, 48.80 ± 1.76%, was observed for A. asplenifolia. The highest TPC values were observed after applying SWE: 93.63 ± 1.01 mg GAE/g DE for A. millefolium, and 90.12 ± 0.87 mg GAE/g DE for A. crithmifolia. The results for TFC revealed a statistically significant difference in values, with A. nobilis subsp. nelreichii as the sample with the highest content of TFC (11.11 ± 0.22 mg QE/g DE) when using UAE. Consequently, it could be concluded that SWE is a superior non-conventional extraction technique, and A. nobilis subsp. nerleichii presents as the most promising plant.