Ethnopharmacology, cytotoxicity, antiviral and immunomodulatory profiles of medicinal plant species used by herbalists in treating people living with HIV/AIDS in Uganda

Abstract

Opportunistic infections (OI) are the single most important cause of mortality and morbidity among PLHIV in poor countries. There is widespread use of medicinal plants among PLHIV. However, there is no scientific information and validation on their toxicity, safety and efficacy. The aim of this study was to document and evaluate the cytotoxicity, anti-HIV-1 and immunomodulatory activities of medicinal plant species used by herbalists in treating PLHIV in Uganda. An ethnopharmacological survey was conducted in Arua, Dokolo, Mbale, Bushenyi, Iganga, Rakai, Luwero and Kaabong districts. Ninety herbalists were interviewed using semi-structured questionnaires. The in vitro cytotoxicity of 11 plant species was determined with the AlamarBlue cell viability assay on the human glioblastoma cell line: U87.CD4.CXCR4. Warburgia ugandensis, Erythrina abyssinica, Cryptolepsis sanguinolenta, Albizia coriaria, Psorospermum febrifugum, Maytenus senegalensis (Sny: Gymnosporia senegalensis), Zanthoxylum chalybeum, Securidaca longipendunculata, Acacia hockii, Gardenia ternifolia Subsp. jovis-tonantis and Bridelia micrantha were screened. Two hundred and thirty-six medicinal plant species from 70 families were documented. There is a high degree of consensus among the TMP on which plant species they use. The herbalists encourage the concomitant use of herbs and ARV and relied on laboratory diagnoses for confirmation of ones sero-status even though they were familiar with the signs and symptoms of HIV/AIDS. The half maximal cytotoxic concentration (CC50) of the extracts was determined. Each plant species had two extracts, DMSO ethanol. The crude plant extracts were tested for antiviral activity against HIV-1 Pseudovirions (PV), HXB2 (IIIB) strain using U87.CD4.CXCR4 cells transfected with the luciferase firefly reporter gene and measured using a luminometer. The selective inhibition of HIV-1 PV was determined using the Selectivity Index (SI). The immunomodulatory effects of the plant extracts were examined using Flow cytometry. The plant extracts were screened for cytotoxicity using the live/dead assay with Peripheral Mononuclear Blood Cells (PMBCs) and for their cytokine inducing activity on IL-2, IL-4, IFN-γ and TNF-α. The plant extracts were also investigated for their cell-proliferation activity. Using regression analysis, exponential curves of fit were drawn in Microsoft Excel 2011. The 50% cytotoxicity values (CC50) of the plant extracts and the coefficient of determination, R2 were calculated. Both the ethanol and DMSO extracts of W. ugandensis (CC50 = 7.6 and 1.5 µg/ml) and A. coriria (CC50 = 6.4 and < 4 µg/ml) were highly cytotoxic. Most of the plant extracts (15/22) were moderately cytotoxic (CC50 = 21-200 µg/ml). The ethanol extracts were generally less toxic than the DMSO extracts. The ethanol extract of P. febrifugum exhibited the highest selective antiviral activity against HIV-1 (SI = 165.8, CC50 = 99.45 µg/ml) with no cytotoxicity at 8 µg/ml. Both the ethanol and DMSO extracts of A. coriaria (CC50 of 6.4 and < 4 µg/ml) and W. ugandensis (7.6 and 1.5 µg/ml) were highly cytotoxic. The flow cytometry results were presented using dot plots. Non-toxic concentrations of the extracts from the live/dead assay ranged from 0.1 µg/ml for W. ugandensis to 30 µg/ml for A. hockii, A. coriaria, B. micrantha, C. sanguinolenta and Z. chalybeaum. The ethanol extract of P. febrifugum stimulated TNF-α and Z. chalybeaum and W. ugandensis stimulated IL-4. None of the extracts showed an effect on T-cell proliferation. In Conclusion, there is wide spread use of medicinal plant species to manage OI and boost immunity in PLHIV in Uganda.