Nrf2-dependent cytoprotective effects and depletion of gut microbial energy harvesting by chemically defined polyphenol-rich Clerodendrum infortunatum

Abstract

Plants belonging to the genus Clerodendrum are consumed as functional foods to treat metabolic liver disease in the North-Eastern sub-Himalayan region of India. The use of Clerodendrum spp. as hepatoprotective is mentioned in Ayurveda and Chinese traditional medicinal literatures. This study identifies a particular Clerodendrum spp. with the most superior bioactivity and evaluates the cellular mechanism behind its cytoprotective activities and its favorable impact on the gut microbiota. Twelve major Clerodendrum spp. were analyzed using GCMS, phytochemical enrichment, pathway analysis, and comparative antioxidant assays were performed. The superior most Clerodendrum sp. was chemically characterized using HPLC and tested against HepG2 and SH-SY5Y cells for cytoprotection using ML385, a pharmacological inhibitor of Nrf2, and its potential to modulate the gut microbiota using 16S rRNA sequencing. Clerodendrum infortunatum was identified as the most bioactive plant sp. with physiologically-relevant free radical scavenging capacities and containing stigmasterol, gallic acid, catechin, syringic acid, vanillic acid, rutin, p-coumaric acid and quercetin. C. infortunatum attenuated intracellular cytoprotective enzymes, lipid peroxidation and protected HepG2 and SH-SY5Y in a Nrf2-dependent manner which were otherwise affected by H₂O₂-induced cellular injury. C. infortunatum also improved gut microbial diversity, enriched the populations of gut commensals, reduced obesogenic microbes, and attenuated gut microbial metabolic functions associated with increased dietary energy harvesting capacity. In accordance to the traditional medicinal use, our data show that the hepatoprotective effects of C. infortunatum is associated with the enhancement of hepatocellular cytoprotection and a favorable modulation of the gut microbiome.