An assessment of the use of an in vitro cell based model of the intestinal tract to investigate the bioavailability of the Chinese herbal remedy Oldenlandia diffusa

Certain Chinese herbal remedies (CHRs) are used to treat cancer. However, their mode of action has yet to be fully elucidated. An earlier study of the anti-cancer activity of one such CHR, Oldenlandia diffusa (Willd.) Roxb (OD) indicated that its cell cytotoxicity: may occur via apoptosis; be cancer cell specific; and involve more than one constituent [1, 2]. However, as this study was carried out in vitro, no information about the impact of the intestinal tract on the anti-cancer activity of this remedy, which is commonly ingested in the form of a tea, was obtained. Thus the aim of this study was to assess the use of a 21 day in vitro model of the intestinal tract to investigate the bioavailability of this CHR. The colon adenocarcinoma cell line Caco-2, in the form of a monolayer, was used to mimic the intestinal tract. The integrity of this model was assessed using the trypan blue exclusion test, transepithelial electrical resistance (TEER), phenol red exclusion and scanning electron microscopy (SEM). Cytotoxicity assessment using trypan blue showed that the model was not adversely affected by OD (ranging in concentration from 15–70%). Phenol red exclusion and TEER measurements showed that the model's integrity was maintained before and after exposure to OD. Furthermore, SEM showed that the monolayer retained its microvilli expression and tight junctions formation before and after exposure to OD. These results demonstrate that this model can be used to study the bioavailability of this CHR.

References: 1. Willimott, S. et al. (2005), Isolation of tumour modulatory compounds in Chinese herbal remedies through activity guided fractionation. Poster at the International Conference and 53^rd Annual Meeting of the Society for Medicinal Plant Research; Florence August 2005. 2. Willimot, S., Barker J., Jones L., and Opara EI. The Chinese herbal medicine Oldenlandia diffusa induces cell-cycle-independent apoptosis in the leukaemic HL60 cell line and growth arrest in PHA-stimulated blood lymphocytes. (in preparation).