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In a previous study, the oral administration of an Aloe vera whole leaf extract induced dose-related mucosal and goblet cell hyperplasia in the rat colon after 13 weeks and colon cancer after 2 years. The primary goal of this study was to determine whether or not the administration of aloin, a component of the Aloe vera plant leaf, would replicate the pathophysiological effects that were observed in rats in the previous study with an Aloe vera whole leaf extract. Groups of 10 male F344/N rats were administered aloin at 0, 6.95, 13.9, 27.8, 55.7, 111, 223 and 446 mg/kg drinking water for 13 weeks. At the end of study, rat feces were collected and the composition of fecal bacteria was investigated by next generation sequencing of the PCRamplified V3/V4 region of the 16S rRNA gene. At necropsy, blood was collected by cardiac puncture and organs and sections of the large intestine were collected for histopathology. Aloin induced dose-related increased incidences and severities of mucosal and goblet cell hyperplasia that extended from the cecum to the rectum, with increased incidences and severities detected at aloin doses⩾55.7 mg/kg drinking water. Analysis of the 16S rRNA metagenomics sequencing data revealed marked shifts in the structure of the gut microbiota in aloin-treated rats at each taxonomic rank. This study highlights the similarities in effects observed for aloin and the Aloe vera whole leaf extract and points to a potential mechanism of action to explain the observed pathological changes via modulation of the gut microbiota composition. [ABSTRACT FROM AUTHOR]

Aloe barbadensis Miller (Aloe vera) is an herbal remedy promoted to treat a variety of illnesses; however, only limited data are available on the safety of this dietary supplement. Drinking water exposure of F344/N rats and B6C3F1 mice to an Aloe vera whole-leaf extract (1, 2, and 3%) for 13 weeks resulted in goblet cell hyperplasia of the large intestine in both species. Based upon this observation, 2-year drinking water studies were conducted to assess the carcinogenic potential of an Aloe vera whole-leaf extract when administered to F344/N rats (48 per sex per group) at 0.5, 1, and 1.5%, and B6C3F1 mice (48 per sex per group) at 1, 2, and 3%. Compared with controls, survival was decreased in the 1.5% dose group of female rats. Treatment-related neoplasms and nonneoplastic lesions in both species were confined primarily to the large intestine. Incidences of adenomas and/or carcinomas of the ileo-cecal and cecal-colic junction, cecum, and ascending and transverse colon were significantly higher than controls in male and female rats in the 1 and 1.5% dose groups. There were no neoplasms of the large intestine in mice or in the 0 or 0.5% dose groups of rats. Increased incidences of mucosa hyperplasia of the large intestine were observed in F344/N rats, and increased incidences of goblet cell hyperplasia of the large intestine occurred in B6C3F1 mice. These results indicate that Aloe vera whole-leaf extract is an intestinal irritant in F344/N rats and B6C3F1 mice and a carcinogen of the large intestine in F344/N rats. [ABSTRACT FROM PUBLISHER]