Aqueous Extracts of Carica papaya Embryogenic Callus Kill Entamoeba histolytica Trophozoites and Orally Protect against the Development of Amoebic Liver Abscesses in Hamsters.

Abstract

Purpose: This study evaluated the anti-amoebic properties of aqueous extracts of two Carica papaya callus clones, Wild Type (Pcc-WT-AE) and KETc7-expressing (Pcc-KETc7-AE) clones, in in vitro and in vivo assays.

Methods: E. histolytica trophozoites cultures were exposed for 24 h to varying concentrations of the C. papaya aqueous extracts, and their viability and IC₅₀ determined by MTT assays. In in vivo studies, golden hamsters were infected intraportally with E. histolytica trophozoites and orally treated with the C. papaya aqueous extracts for 7 days. The animals were sacrificed on day 8, and the development of ALA was recorded. Comparisons were made against metronidazole (MTZ).

Results: Both extracts statistically reduced trophozoite viability at 24 h in a dose-dependent manner in vitro. Pcc-KETc7-AE showed activity to the same extent as MTZ (IC₅₀ 36.08 µg/ml vs. 33.54 µg/ml, respectively), whereas Pcc-WT-AE exhibited less efficient but significant activity (IC₅₀ 113.4 µg/ml). Cell death analysis indicated that both extracts killed trophozoites by necrosis. In vivo studies showed that oral treatment with Pcc-WT-AE (4 and 8 mg/dose/hamster) completely prevented ALA development in 80% of animals, comparable to the effect of MTZ. In contrast, oral treatment with Pcc-KETc7-AE did not prevent lesions, but statistically reduced hepatomegaly, ALA size, and necrotic areas in tissue sections.

Conclusion: The aqueous extracts from C. papaya embryogenic callus cultures analyzed here exhibit potent, yet variable, anti-E. histolytica activity in both in vitro and in vivo studies. The activity was nearly as effective as MTZ suggesting their potential use as a new, natural and safe oral treatment for amebiasis.