Chemical Characterization and Anti-Inflammatory Activity of Flavonoid Fraction of Garlic Skin Extract: A Potential Source of Natural Anti-Inflammatory Agents

Background: Garlic skin, a discarded byproduct of Nigeria’s 136,000-ton annual garlic production, poses an environmental challenge yet holds untapped potential as a source of bioactive compounds. Flavonoids from such waste could provide sustainable alternatives to synthetic anti-inflammatory drugs, though garlic skin’s therapeutic properties remain underexplored. Aim: This study aimed to characterize the phytochemical profile of a flavonoid-rich fraction from garlic skin extract (FRFGS) and evaluate its anti-inflammatory efficacy in vivo. Methods: Garlic skins from Imo State farmers were methanol-extracted, partitioned with ethyl acetate to isolate FRFGS, and analyzed using FT-IR, HPLC, and GC-FID. Total flavonoid content was quantified against a quercetin standard. Anti-inflammatory activity was tested in a carrageenan-induced paw oedema rat model at doses of 100, 200, and 400 mg/kg, compared to Diclofenac (50 mg/kg), with TNF-α and IL-6 levels assessed via ELISA. Results: FRFGS yielded 32.08 ± 2.88 mg/g quercetin-equivalent flavonoids, revealing mainly silymarin, ellagic acid, catechin, luteolin, flavone, quercetin, and kaempferol through HPLC and GC-FID analysis. FT-IR detected functional groups indicative of bioactive molecules. FRFGS exhibited dose-dependent oedema inhibition, with 200 mg/kg achieving 49% reduction (p<0.05) after one week, surpassing Diclofenac’s 42%, and significantly reduced TNF-α and IL-6 (p<0.01). No acute toxicity was observed at tested doses. Conclusion: Garlic skin’s flavonoid-rich fraction offers potent anti-inflammatory activity, comparable to Diclofenac, and a favourable safety profile, positioning it as a sustainable natural therapeutic resource. These findings underscore its potential for clinical development in inflammation management.