Orange-fleshed sweet potato (Ipomoea batatas) extract attenuates lipopolysaccharide-induced inflammation in RAW264.7 cells via inactivation of MAPKs and IkB signalling

Abstract

Introduction: Orange-fleshed sweet potato (OFSP) is an excellent source of β-carotene. Due to its health benefits, β-carotene-rich plants are receiving attention. This study aimed to assess the inhibitory effect of the ethanol extract of steamed OFSP on lipopolysaccharide (LPS)-induced inflammation in murine macrophage cell line (RAW 264.7 cells). Methods: β-carotene, total phenolics and total flavonoids of OFSP were measured by high performance liquid chromatography (HPLC), the Folin- Ciocalteu assay and the aluminum chloride colorimetry, respectively. RAW264.7 cell monolayers were pre-treated with 0.5-2.0 mg/mL ethanol extract from steamed OFSP prior to co-incubation with or without LPS for 24 h. Culture media and cell lysate were collected to measure nitric oxide, interleukin-6 (IL-6), IL-1b, tumour necrosis factor-a, inducible nitric oxide synthase, cyclooxygenase-2, mitogenactivated protein kinases (MAPKs) and inhibitory kappa B (IkB), respectively. Results: The ethanol extract from steamed OFSP significantly suppressed LPSinduced production of such pro-inflammatory mediators by the inactivation of MAPKs and IkB signalling pathway. The ethanol extract from steamed OFSP contained 226 μg/g DW (dry weight) of β-carotene, 2.13 mg gallic acid equivalent/g DW of total polyphenolics and 0.24 mg quercetin equivalents/g DW of total flavonoids. Conclusion: These results indicated that bioactive compounds in steamed OFSP have anti-inflammatory potential.