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Topical Area: Dietary Bioactive Components

Dietary Bioactive Components (Poster Session)

(P03-072-23) Anti-Inflammatory Effects of Digested Onion Peel Extract on Lipopolysaccharide-Induced RAW 264.7 Cells

Saturday, July 22, 2023
12:00 PM – 1:00 PM ET
Location: Poster Board 487
Disclosure(s):
Saad A. Sifat, MS: No relevant financial relationship(s) with ineligible companies to disclose.
Inah Gu, M.S.: No relevant financial relationship(s) with ineligible companies to disclose.
Olugbenga T. Balogun, Master's degree: No relevant financial relationship(s) with ineligible companies to disclose.


Objectives: Onion peels are high in bioactive compounds that have potent antioxidant and anti-inflammatory effects. The objective of the study was to analyze the anti-inflammatory effects of in-vitro digested onion peel (dOPE) extract using RAW 264.7 cells.

Methods: Both undigested onion peel extract (OPE) and dOPE were analyzed for the phenolic profile using HPLC. To assess cell viability and nitric oxide (NO) inhibition activities, RAW 264.7 cells were pretreated with dOPE extracts at concentrations of 1-250 μg/mL for 1hr and stimulated with lipopolysaccharide (LPS, 100ng/mL). Cell viability and NO production were measured using the Cell Proliferation assay and Griess reaction system, respectively. Pro-inflammatory cytokine (TNF- α, tumor necrosis factor-α) was measured using an ELISA kit. All data were analyzed using the ANOVA procedure (JMP Pro, Version 17.0.0) with significance at P< 0.05 level.

Results: The total phenolics content in OPE and dOPE was 18.1 g/100g and 26.3 g/100g of dry extract, respectively, and the quercetin content was 8604.6 ± 42.4 mg/100g and 16079.5 ± 123.5 mg/100g dry extract. There was no significant difference in cell viability between the control and the group pretreated with dOPE concentrations (up to 250 µg/mL). After inducing inflammation with LPS, 150 µg/mL and 200 µg/mL of dOPE treatments were not significantly different in suppressing NO production compared to dexamethasone (15 µM, inflammation drug). dOPE (50 µg/mL) did not lower the level of TNF-α.

Conclusions: The finding showed that dOPE has a higher concentration of phenolic compounds, including quercetin, compared to OPE. dOPE showed the NO inhibitory effects but not TNF-α level, suggesting that further studies are needed to understand the cytokines suppression properties of dOPE.

Funding Sources: No particular grant for this research was received from any funding agency in the public, commercial, or not-for-profit sectors.