Hypocholesterolaemic mechanism of bitter melon aqueous extracts via inhibition of pancreatic cholesterol esterase and reduction of cholesterol micellar solubility

Triterpenoids from Protorhus longifolia Exhibit Hypocholesterolemic Potential via Regulation of Cholesterol Biosynthesis and Stimulation of Low-Density Lipoprotein Uptake in HepG2 Cells

The increasing incidence of hypercholesterolemia-related diseases even in the presence of the currently available cholesterol-lowering drugs indicates a need to discover new therapeutic drugs. This study aimed to investigate the hypocholesterolemic potential of two triterpenoids isolated from Protorhus longifolia stem bark. In silico techniques and in vitro enzyme assays were used to evaluate the potential inhibition of cholesterol esterase and HMG-CoA reductase by the triterpenoids (ARM-2 and RA-5). The toxicity, modulation of low-density lipoprotein (LDL) uptake, and associated gene expression were determined in HepG2 hepatocytes. In silico molecular docking revealed that ARM-2 compared with RA-5 has a relatively stronger binding affinity for both enzymes. Both triterpenoids further demonstrated promising in silico drug-likeness properties and favorable ADMET profiles characterized by high intestinal absorption and lack of CYP450 enzyme inhibition. The compounds further showed, to varying degrees of efficacy, inhibition of cholesterol micellization as well as both cholesterol esterase and HMG-CoA reductase activities with IC50 values ranging from 16.4 to 41.1 μM. Moreover, enhanced hepatic cellular LDL uptake and the associated upregulation of the LDL-R and SREBP-2 gene expression were observed in the triterpenoid-treated HepG2 cells. It is evident that the triterpenoids, especially ARM-2, possess hypocholesterolemic properties, and these molecules can serve as leads or structural templates for the development of new hypocholesterolemic drugs.

Identification and characterization of cholesterol esterase and lipase inhibitory peptides from amaranth protein hydrolysates

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Gastric, microbial and plant-based enzymes were used to produce Amaranth protein hydrolysates (APHs).

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APHs displayed enhanced cholesterol esterase (CEase) and pancreatic lipase (PL) inhibitory activities.

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Bromelain generated hydrolysates showed the highest CEase and PL inhibitory activity.

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FPFPPTLGY, FGAPR, and FPFVPAPT were predicted as potential PL inhibitors and FPFVPAPT as CEase inhibitor.

Human diet is undergoing a shift towards plant-based diet as a sustainable source of protein compared to animal-derived protein. In this study, cholesterol esterase (CEase) and pancreatic lipase (PL) inhibitory activities of amaranth protein hydrolysates (APHs) were studied. Bromelain, chymotrypsin, and actinase E were used for generating APHs at 2, 4 & 6 h of hydrolysis. Higher PL inhibiting potential were observed in bromelain-derived APHs (IC₅₀ = 0.38–0.66 mg/mL) in comparison to intact amaranth proteins (IC₅₀ = 3.93 mg/mL). Bromelain-4 h hydrolysates (AB4) demonstrated significant inhibitory potential for both CEase (IC₅₀ = 0.47 mg/mL) and PL (IC₅₀ = 0.48 mg/mL) activity. Peptide identification in AB-4 hydrolysate revealed that among 17 bioactive peptides, three peptides (FPFPPTLGY, FGAPR, and FPFVPAPT) were predicted as potential PL inhibitors and only one peptide (FPFVPAPT) was predicted as CEase inhibitor based on the number of substrate binding sites on active site of the enzymes. This is the first study providing insights into amaranth protein derived bioactive peptide possessing CEase and LIP inhibitory potential.

Potential Hypolipidemic Effects of Banana Condensed Tannins Through the Interaction with Digestive Juice Components Related to Lipid Digestion

An in vitro intestinal model was used to evaluate the impact of banana condensed tannins (BCT) on the digestion of lipids (fat and cholesterol). BCT significantly suppressed the digestion of fat and cholesterol by interacting with digestive juice components. The interactions of BCT with a digestive juice mixture and its components (including bile acid, lipase, cholesterol esterase, CaCl₂, NaCl, and cholesterol) were analyzed using turbidity, isothermal titration calorimetry, particle size distribution, zeta potential, and molecular docking analyses. The results showed that BCT reduced the digestion of lipids mainly via interaction with lipase, cholesterol esterase, bile acid, and cholesterol. Electrostatic CT-calcium ion complexes might reduce the extent of lipid digestion by decreasing the surface area of the lipid droplets exposed to the enzymes. This research provides valuable insights into the molecular mechanisms of the interaction of BCT with digestive juice components related to lipid digestion that may affect the rate and extent of lipid digestion.

Phenolic compounds from an Algerian medicinal plant (Pallenis spinosa): simulated gastrointestinal digestion, characterization, and biological and enzymatic activities

Pallenis spinosa is a medicinal plant which is used in folk medicine as curative or preventive remedies for various diseases. Individual phenolic compounds from the methanolic extracts of its flowers, leaves and stem were determined by the high performance liquid chromatography method (HPLC) and total phenolic contents (TPC) were evaluated by Folin-Ciocalteu assay. The stability and bioactivity (antioxidant activity, micellar cholesterol solubility, α-amylase, and angiotensin converting enzymes (ACE) inhibitory effects) of these extracts in the gastrointestinal environment was determined before and after their protection in hydroxypropylmethylcellulose (HPMC) capsules. HPLC analysis revealed the presence of thirteen phenolic compounds with nine flavonoids and four phenolic acids. Except for kaempferol, the twelve other compounds have not been previously detected in the aerial part of the studied plant. Quantification of phenolics by HPLC and Folin Ciocalteu methods revealed that the highest TPC was detected in the flower extracts (104.31 ± 0.80 and 145.73 ± 0.48 mg EGA per g of extract, respectively). Leaf extracts displayed the best antioxidant capacity against the two tested radicals DPPH and ABTS (IC50 = 1.24 ± 0.03 and 0.94 ± 0.02 mg mL-1, respectively), FRAP assay (IC50 = 0.50 ± 0.02 mg mL-1), α-amylase inhibitory (IC50 = 1.25 ± 0.00 mg mL-1) and angiotensin activity with an inhibitory percent of 30.10 ± 0.12%. The best activity shown by stem extracts was against micellar cholesterol solubility (67.57 ± 0.00%). A strong decrease in TPC and their bioactivity was observed after the gastrointestinal digestion (GID) in non encapsulated extracts. These results showed that P. spinosa is a good source of phenolic compounds and GID affects significantly their composition, content and bioactivity.

Siamese neem flower extract suppresses cholesterol absorption by interfering NPC1L1 and micellar property in vitro and in intestinal Caco-2 cells

Siamese neem (Azadirachta indica A. Juss var. siamensis Valeton) (A. indica) leaf extract, a traditional ayurvedic medicine, has been reported to exhibit antipyretic, antibacterial, antidyslipidemic, and antihyperglycemia effects. This study investigated the mechanism of hypocholesterolemic effect of methanolic extract of Siamese neem flowers in in vitro studies and in Caco-2 cells. Pancreatic cholesterol esterase and 3-hydroxy 3-methylglutaryl-CoA (HMG-CoA) reductase activities were assessed. Cholesterol micelle formation was prepared for in vitro cholesterol physicochemical property analyses, micelle size and solubility, and transport of cholesterol into the Caco-2 cells. The expression of niemann-pick C1 like 1 (NPC1L1), and its major regulator, peroxisome proliferator-activated receptor δ (PPARδ), were determined by western blot and real time polymerase chain reaction, respectively. A. indica flower extract inhibited pancreatic cholesterol esterase activity and increased cholesterol micelles size. Uptake of cholesterol into Caco-2 cells was inhibited by A. indica flower extract in a dose-dependent manner. In addition, A. indica extract inhibited HMG-CoA reductase activity, resulting in low level of intracellular cholesterol accumulation, together with increased cytosolic NPC1L1 protein expression and decreased PPARδ gene expression. In conclusion, A. indica flower extract has cholesterol-lowering effects by inhibiting intestinal cholesterol absorption, interfering micellar cholesterol formation, and attenuating cholesterol synthesis. As such, A. indica flower extract has potential for developing into nutraceutical product for prevention of hypocholesterolemia.