Anti-Inflammatory and Antioxidant Properties of Ethanol Extracts of Raw, Blanched, Steamed, and Sous-Vide Cooked Okra (Abelmoschus esculentus L.) in LPS or H2O2-Treated RAW264.7 Cells

Abstract

Okra (Abelmoschus esculentus L.) is a plant belonging to the Malvaceae family. All parts of okra, including the pod, leaf, and branch, are edible, with the pod being especially enriched with sugars, dietary fibers, minerals, vitamins, and antioxidants. It has beneficial effect against colitis, hepatitis, and gastric ulcer. However, studies on okra’s anti-inflammatory effects remain limited. It is known that cooking methods change nutrition and functional compounds in foods. In this study, we prepared ethanolic extracts of okra using four different cooking methods (raw, blanching, steaming, and sous-vide), and analyzed anti-inflammatory and antioxidant effects on lipopolysaccharide- (LPS) or hydrogen peroxide (H2O2)-treated RAW264.7 macrophages. Cell viability was similar between all four cooking methods, confirming that okra extracts (≤200 μg/mL) were not cytotoxic. All cooking methods inhibited nitric oxide production (indicator of inflammatory responses). Sous-vide cooking showed low inhibitory effect at 100–200 μg/mL of okra extract. Moreover, examining the mRNA expression of inducible cycloxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and inflammatory cytokines (tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1-beta (IL-1β)) showed inhibitory effects by all cooking methods. Reactive oxygen species (ROS) levels were also reduced for all cooking methods, with sous-vide cooking showing the highest rate of reduction. These results confirm the anti-inflammatory and antioxidant effects of raw and multimethod cooked okra. Notably, sous-vide cooking showed the greatest potential to improve okra’s therapeutic effects.