In vitro anti-Herpes simplex virus activity of crude extract of the roots of Nauclea latifolia Smith (Rubiaceae)

Nauclea latifolia Smith, a shrub belonging to the family Rubiaceae is a very popular medicinal plant in Cameroon and neighboring countries where it is used to treat jaundice, yellow fever, rheumatism, abdominal pains, hepatitis, diarrhea, dysentery, hypertension, as well as diabetes. The ethno-medicinal use against yellow fever, jaundice and diarrhea prompted us to investigate on the antiviral activity of the root bark of N. latifolia. In this study, HSV-2 was chosen as a viral model because of its strong impact on HIV transmission and acquisition.

The results of this work partly justify the empirical use of N. latifolia in traditional medicine for the treatment of viral diseases. This extract could be a promising rough material for the development of a new and more effective modern anti-HSV-2 medication also active against acyclovir-resistant HSV-2 strains.

The crude extract under study was prepared by maceration of air-dried and powdered roots barks of N. latifolia in CH2Cl2/MeOH (50:50) mixture for 48 hours, then it was subjected to filtration and evaporation under vacuum. A phytochemical analysis of the crude extract was performed by High Performance Liquid Chromatography coupled with a photodiode array and mass spectrometry (HPLC-PDA-ESI-qMS). The anti-HSV-2 activity was assayed in vitro by plaque reduction and virus yield assays and the major mechanism of action was investigated by virucidal and time of addition assays. Data values were compared using the Extra sum of squares F test of program GraphPad PRISM 4.

The main components detected in the extract belong to the class of indole alkaloids characteristic of Nauclea genus. Strictosamide, vincosamide and pumiloside were tentatively identified together with quinovic acid glycoside. N. latifolia crude extract inhibited both acyclovir sensitive and acyclovir resistant HSV-2 strains, with IC50 values of 5.38 μg/ml for the former and 7.17 μg/ml for the latter. The extract was found to be most active when added post-infection, with IC50 of 3.63 μg/ml.