In Vitro Antioxidant Activity and Gastrointestinal Effect of the Decocted Extract of Hibiscus sabdariffa

Abstract

The present study investigated the phytochemical content, antioxidant activity, and gastrointestinal motility effects of the aqueous extract of Hibiscus sabdariffa L (HSAq). The results showed that the extraction yield was 33.7%. Quantitative analysis revealed moderate amounts of bioactive compounds, including total polyphenols (73.49 ± 9.83 µg GAE/mg extract), flavonoids (8.44 ± 0.77 µg QE/mg extract), and tannins (51.83 ± 2.05 µg TAE/mg extract). HSAq exhibited notable antioxidant properties across multiple assays: DPPH radical scavenging (IC50 = 149.17 ± 0.12 µg/ml), ABTS assay (IC50 = 239.79 ± 26.38 µg/ml), phenanthroline-based reducing power (EC50 = 23.08 ± 6.77 µg/ml), and total antioxidant capacity (EC50 = 216.8 ± 7.53 µg/ml). Gastric emptying (GE) evaluations showed that HSAq at a dose of 400 mg/kg did not significantly modify gastric emptying (79.62 ± 2.40%). Therefore, HSAq significantly inhibited intestinal transit (IT) in a dose-dependent manner, with the dose of 400 mg/kg showing the highest inhibition (42.11 ± 1.59%). The inhibition and activation of nitric oxide (NO) synthase with L-NNA or L-arginine showed that the NO pathways are not involved in the effect induced by HSAq. Meanwhile, regarding the cyclooxygenase (COX) pathway, inhibition of COX by Indometacin decreased IT (44.25 ± 3.92%), and this reduction persisted in the presence of HSAq (51.73 ± 4.34%). This explains that the HSAq effect is mediated by the synthesis inhibition of PG. These findings support the potential therapeutic use of HSAq as an antioxidant agent with selective inhibitory effects on intestinal motility, without affecting normal gastric emptying.