Anti-Inflammatory, Antidiabetic, and Antioxidant Properties of Extracts Prepared from Pinot Noir Grape Marc, Free and Incorporated in Porous Silica-Based Supports

Abstract

This study presents properties of hydroethanolic extracts prepared from Pinot Noir (PN) grape pomace through conventional, ultrasound-assisted or solvothermal extraction. The components of the extracts were identified by HPLC. The total content of polyphenols, flavonoids, anthocyanins, and condensed tannins, as well as antioxidant activity and α-glucosidase inhibitory activity of extracts were evaluated using UV-vis spectroscopy. All extracts were rich in phenolic compounds, proving a good radical scavenging activity. The extract obtained by conventional extraction at 80 °C showed the best α-glucosidase inhibitory activity close to that of (-)-epigallocatechin gallate. To improve the chemical stability of polyphenols, the chosen extract was incorporated in porous silica-based supports: amine functionalized silica (MCM-NH₂), fucoidan-coated amine functionalized silica (MCM-NH₂-Fuc), MCM-41, and diatomite. The PN extract exhibited moderate activity against Gram-positive S. aureus (MIC = 156.25 μg/mL) better than against Gram-negative E. coli (MIC = 312.5 μg/mL). The biocompatibility of PN extract, free and incorporated in MCM-NH₂ and MCM-NH₂-Fuc, was assessed on RAW 264.7 mouse macrophage cells, and the samples showcased a good cytocompatibility at 10 µg/mL concentration. At this concentration, PN and PN@MCM-NH₂-Fuc reduced the inflammation by inhibiting NO production. The anti-inflammatory potential against COX and LOX enzymes of selected samples was evaluated and compared with that of Indomethacin and Zileuton, respectively. The best anti-inflammatory activity was observed when PN extract was loaded on MCM-NH₂-Fuc support.

Keywords: anti-inflammatory properties; antidiabetic activity; antioxidant activity; extract encapsulation; grape marc; phenolic extract; porous silica.

Figure 1

Spectrometric determinations for the prepared extracts: TP as gallic acid equivalents, GAE (A); TF as quercetin equivalents, QE (B); TAC as cyanidin-glucoside equivalents, CGE (C); RSA as Trolox equivalents, TE (D).

Figure 2

Small-angle X-ray diffraction patterns of MCM-41-type support (A); FTIR spectra of diatomite, MCM-NH₂, MCM-NH₂-Fuc, and fucoidan denoted Fuc (B); Wide-angle XRD analysis of diatomite (C); SEM micrographs of MCM-NH₂ sample (D), MCM-NH₂-Fuc support (E), sulfur (red) mapping of MCM-NH₂-Fuc surface (F), and diatomite (G).

Figure 3

TGA-DTA curves for MCM-NH₂ and MCM-NH₂-Fuc supports.

Figure 4

TGA-DTG curves of PN (A), PN@MCM-NH₂ and PN@MCM-NH₂-Fuc (B); as well as for PN@MCM-41 and PN@Diatomite (C).

Figure 5

XRD patterns of PN, PN(C), PN@diatomite, and PN@MCM-41 (A); FTIR spectra of PN@diatomite in comparison with that for PN extract (B); radical scavenging activity of PN@MCM-41 and PN@Diatomite in comparison with that of PN free extract and corresponding supports using DPPH solution as control after 12 months of storage at 4 °C (C).

Figure 6

Cell viability and NO production inhibitory effects in RAW 264.7 cells. (A) Cellular viability after 72 h of exposure to the test samples compared to the Control group (Untreated cells). (B) NO generation in cells treated with the different test samples for 1 h before the addition of LPS and induction of inflammation as compared to the Control (cells that received LPS only). The symbol (*) indicates significant difference from the control, while the symbol (♦) refers to significant difference from 10 µg/mL concentration of the test sample. The use of each symbol for once, twice, and thrice indicate p-values < 0.05, <0.01, and <0.001, respectively. (C) Anti-inflammatory potential against COX-1 and COX-2 in comparison with Indomethacin, and LOX compared to Zileuton. Data displayed as the average of triplicates ± standard deviation (SD).