Anthelmintic screening of five palmatilobae species used in Traditional Medicine in Katanga Province (DR Congo)

Aim of the study: resistance to known anthelmintics has become a growing concern. Based on 2017-2019 ethnomedical and ethnoveterinary surveys carried out in Katanga Province, several species of shrub locally identified as Vitex species (Lamiaceae) are used to treat helminthiases. In this study, 5 of these species, including different morphotypes, were selected for in vitro screening in order to search for new anthelmintic lead compounds.

Method: n-heptane, dichloromethane (DCM), ethyl acetate (EtOAc) and methanol (MeOH) extracts of selected plants (leaves, root barks and stem barks) were evaluated for their anthelmintic activity. The experiment was assessed using a standard motility assay on the N2 wild-type Caenorhabditis elegans strain.
Results: anthelmintic activity was confirmed by the calculation of motility inhibition. The following extracts, tested at 200 μg extract/mL, were significantly active on this model (average ± SD; n = 3; positive control, levamisole, 50 μM : 98.7 ± 4.3% of motility inhibition) : Oldfieldia dactylophylla (Welw. ex Oliv.) (Picrodendraceae; locally misidentified as V. congolensis De Wild and T. Durand) [DCM leaves (71.0 ± 5.7%), MeOH stem barks (90.0 ± 7.3%) and MeOH stem roots (97.0 ± 5.9%)] ; V. doniana Sweet [EtOAc leaves (64.0 ± 4.4%)] ; V. fischeri Gürke [n-heptane leaves (98.0 ± 7.8%)] ; V. madiensis subsp. Milanjiensis (Britten) F. White [DCM leaves 3-5 leaflets (65.0 ± 5.6%) and 5 leaflets (69.0 ± 6.6%)] and V. mombassae Vatke [DCM leaves 3-5 leaflets (62.0 ± 8.1%)].
Conclusion: the motility inhibitions measured on the N2 wild-type Caenorhabditis elegans model provide support for the traditional use of these plants and call for further studies to develop compounds as possible treatments for parasitic worm infections. The misidentification of Oldfieldia dactylophylla seems to be general in the study region.