Metabolomic fingerprinting of phenolic compounds in blood serum from rats treated with chestnut shells extract

The intake of dietary phenolic compounds has clearly boosted in the last decades owing to their health-promoting benefits with protective effects against chronic pathologies. Beyond fruits and vegetables, food by-products have also been recognized as promising sources of phenolic compounds. Chestnut shells (CS) are one of these agro-industrial by-products [1, 2]. Although recent studies have proposed the CS valorization as an added-value resource with innovative applications in nutraceutical industry, metabolomic studies should be accomplished to attest the in vivo health effects.

The purpose of this study was to explore the targeted metabolomic profile of phenolic compounds in rat blood serum, following the acute intake of two doses of CS extract (50 and 100 mg/kg b.w.) administered by gastric gavage. The dried and powdered CS were extracted by a green technology, namely Subcritical Water Extraction (SWE), at 220 °C for 30 min [1]. The animal studies were carried out daily for 7 days and blood was collected by cardiac puncture. For metabolomic studies, a LC-ESI-LTQ-Orbitrap-MS analysis was employed in negative mode [3]. Phenolic compounds and metabolites were identified using commercial standards and comparing with databases and literature data.

The results attested the presence of metabolites of phase I (hydrolysis, oxidation, and hydrogenation) and phase II (glucuronidation, methylation and sulfation) reactions. The higher number of metabolites identified were from phenolic acids, including caffeic acid, coumaric acid, ellagic acid, ferulic acid, gallic acid, hydroxybenzoic acid, protocatechuic acid, and syringic acid. Lignans and phase II metabolites were also present, while only one flavanol metabolite was detected. Pyrogallol and catechol metabolites were also noticed. The outcomes enlighten the metabolomic mechanisms in blood serum underlying the acute intake of phenolics-enriched CS extract with proven antioxidant properties by in vitro assays. Notwithstanding, ongoing studies regarding the quantification of phenolic compounds and metabolites are still being attempted.