In vitro and in vivo anti-inflammatory properties of Annona muricata, Launaea taraxacifolia and Tridax procumbens leave extracts

Abstract

Background In recent years, the role of inflammation in the development of several non-communicable diseases such as diabetes, cardiovascular diseases and cancer has been increasingly highlighted. Many medicinal plants contain bioactive substances with anti-inflammatory activities. The objective of this work was to study cytotoxicity and anti-inflammatory activity of hydroethanolic extracts of the leaves of Annona muricata, Launaea taraxacifolia and Tridax procumbens, three plants used in traditional medicine in Benin. Method Cytotoxicity and anti-inflammatory activity of the extracts was first assessed in vitro on the human monocyte THP-1 cells. In vitro, cytotoxicity was measured using the lactate dehydrogenase (LDH) assay. LPS/IFNγ-activated THP-1 cells were used to evaluate the anti-inflammatory effect of the three extracts by measuring gene expression level of pro-inflammatory (COX2, TLR8) and anti-inflammatory (IL-10-Receptor 1) markers by RT-qPCR, and by measuring by ELISA the production of pro- and anti-inflammatory cytokines (TNF, IL1β, IL-10) by THP-1 cells. Second, the model of acute Wistar rat hind paw edema induced by 1% formalin was used for the in vivo anti-inflammatory test. Results In vitro, the three plant extracts were nontoxic to THP-1 cells until 250 µg/mL. Expression of the pro-inflammatory markers COX2 and TLR8 were significantly lower for LPS/IFN_ϒ activated-cells treated with plant extracts at 50 and 100 µg/mL compared to untreated activated cells (P ˂ 0.05). IL-10-R1 expression was similar in untreated and plant-treated LPS-IFN_ϒ activated-cells, except for treatment with 50 µg/mL L. taraxacifolia leaf extract which resulted in lower expression of IL-10-R1. The production of TNF was completely abolished following the three plant treatment at 100 µg/mL of LPS/IFN_ϒ activated-cells, while IL-1β production was reduced (P < 0.001). For the anti-inflammatory cytokine IL-10, the production was higher by activated cells after treatment with 100 µg/mL L. taraxacifolia extract compared to untreated activated cells (P < 0.05). In vivo, per os administration of the three extracts at 300 mg/kg significantly prevented paw edema in rats (P < 0.05), similarly to acetylsalycilic acid. Conclusion The results suggest that the hydro-ethanolic extracts of the three plants have significant anti-inflammatory properties and deserve further studies for their use in the treatment of inflammatory pathologies.