The effect of derum (bark of Juglans regia tree) extract on oral mucosa: An in vivo study based on epithelial atypia in rabbit model

Background and objectives

Derum, the bark of walnut tree (Juglans regia) has been used as a traditional tooth cleanser and chewed for its ability to bestow purple color to oral mucosa, tongue and lips Studies have shown that derum extract could affect oral epithelium after long term exposure, causing dysplasia. The aim of this in-vivo study was to evaluate the degree of epithelial dysplasia caused by varying durations and frequencies of topical derum application on oral mucosa of rabbits.

Materials and Methods

Following ethical approval, derum extract was applied to the buccal vestibule of New Zealand white rabbits over three different periods (60 days, 120 days, 180 days) and two different protocols were used (daily application and once every 3 days). Accordingly, the animals were divided into four groups (A – daily derum application/B – derum applied once in 3 days/C – Positive control and acetone applied every alternate day/D – negative control), and three batches (I – 60 days/II – 120 days/III – 180 days). The animals were sacrificed, and oral biopsies prepared and examined under light microscope. The magnitude of epithelial changes was evaluated using epithelial atypia index (EAI) based on Smith and Pindborg histological grading system (1969) for epithelial dysplasia.

Results

Mild dysplastic changes were detected in animals treated with derum extract regardless of the period of application. Similar results were noted among positive control group, and highest score was recorded in group A followed by group B with high tendency towards long-term derum application. Moderate changes were encountered only in group A that received derum for 180 days. Statistically, long-term derum application (180 days / Batch III in groups A and B), irrespective of the frequency of application, resulted in significantly higher mean EAI scores than all other groups or batches.

Conclusion

Based on this study, prolonged and frequent use of derum can induce dysplastic changes in rabbit oral mucosa, ranging from mild to moderate dysplasia. Further studies with extended times of exposure of derum to oral mucosa are recommended to document these adverse effects as an evidence base.