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Natural products play an important role in cancer therapeutics, and lately more attentions have been paid to the prevention of major lethal malignancies, such as colorectal cancer (CRC). After oral ingestion, botanicals' parent compounds can be converted to their metabolites by the enteric microbiome, and these metabolites may have different bioactivities and variable bioavailability. In this study, we used an active ginseng metabolite, protopanaxadiol (PPD), as an example to assess its colon cancer preventive effect by comparing its effect with the treatment effect of fluorouracil (5-FU). A xenograft tumor nude mouse model with human colon cancer cell inoculation was used. After preventive PPD or treatment 5-FU administration with the same dose (30 mg/kg), tumor growth inhibition was evaluated by both a Xenogen bioluminescence imaging technique and manual tumor size measurement. Our data showed that preventive PPD very significantly inhibited the tumor growth compared to 5-FU (p < 0.01). Our data suggest that the PPD is a promising cancer prevention agent. More studies are needed to explore the chemopreventive actions of PPD and its potential clinical utility.

Asian ginseng, American ginseng, and notoginseng are three major species in the ginseng family. Notoginseng is a Chinese herbal medicine with a long history of use in many Oriental countries. This botanical has a distinct ginsenoside profile compared to other ginseng herbs. As a saponin-rich plant, notoginseng could be a good candidate for cancer chemoprevention. However, to date, only relatively limited anticancer studies have been conducted on notoginseng. In this paper, after reviewing its anticancer data, phytochemical isolation and analysis of notoginseng is presented in comparison with Asian ginseng and American ginseng. Over 80 dammarane saponins have been isolated and elucidated from different plant parts of notoginseng, most of them belonging to protopanaxadiol or protopanaxatriol groups. The role of the enteric microbiome in mediating notoginseng metabolism, bioavailability, and pharmacological actions are discussed. Emphasis has been placed on the identification and isolation of enteric microbiome-generated notoginseng metabolites. Future investigations should provide key insights into notoginseng’s bioactive metabolites as clinically valuable anticancer compounds.