Antioxidant and anti-inflammatory activities of Cameroon nutritional spice extracts in human gastric epithelial cells

In Cameroon, many medicinal plants, including spices, are used as herbal medicines and traditionally employed for the treatment of gastric diseases, in which oxidative stress is involved. The present work chemically characterizes and investigates the antioxidant and anti-inflammatory effect of hydro-alcoholic extracts of eleven Cameroonian spices at gastric level, focusing on Nuclear Factor (NF)-κB pathway. Prepared hydro-ethanolic extracts were characterized by HPLC-DAD and GC/MS analysis, then screened for their ability to inhibit tumor necrosis factor (TNF)α-induced IL-8 and IL-6 release, in human gastric epithelial cells (GES-1 and AGS), assessing the involvment of NF-κB driven transcription. The antioxidant activity of the extracts was evaluated as well. After a preliminary screening, Xylopia parviflora, Tetrapleura tetraptera, Dichrostachys glomerata, Aframomum melegueta, and Aframomum citratum extracts were chosen for in-depth studies. They reduced in a concentration-dependent fashion the cytokines release (IC50s between 0.19 µg/mL and 20 µg/mL) and the NF-κB driven transcription (IC50s between 0.33 µg/mL and 20 µg/mL). They also showed a highest antioxidant capacity measured by ORAC (range: 2.52–11.88 μM Trolox Eq/g of extract), FRAP (range: 40.23–233.84 mg gallic acid Eq/g of extract) and Total phenols (range: 8.96-32.96% mg gallic acid Eq/g of extract) assays. Chemical analysis suggested that their secondary metabolites (androstenone, chlorogenic acid, pimaric acid, catechin, caffeic acid and its derivatives, 4ʹ,5,7-trihydroxyflavanone, gingerol, shogaol, paradol and gallotannins) could potentially justify the biological properties observed. Results obtained from this study showed that the extracts reduce oxidative stress and inflammatory markers by scavenging free radicals and impairing NF-κB signaling at gastric level. However, other molecular mechanisms cannot be excluded, and further studies are needed to better clarify their biological activities.