Anti-nitric oxide production, anti-proliferation and antioxidant effects of the aqueous extract from Tithonia diversifolia

ABSTRACT

Objective: To determine the cytotoxicity, reduction in nitric oxide production and anti-oxidative activity of the aqueous leaf extract from Tithonia diversifolia (T. diversifolia) in an in vitro model. Methods: Leaves of T. diversifolia were collected from natural habitats and extracted with distilled water using the decoction method. The cytotoxic effect of the extract in terms of cell viability was determined using RAW264.7 cells and human peripheral blood mononuclear cells (PBMCs) via the mitochondrial respiration method using the MTT reagent. The effect of the extract on lipopolysaccharide (LPS)-induced nitric oxide pro-duction in RAW264.7 cells was measured using the Griess reagent. The chemical anti-oxidant was evaluated by ABTS-and DPPH-radical scavenging assays. Results: The half-maximal cytotoxic concentration values were 145.87 mg/mL and 73.67 mg/mL for human PBMCs and RAW264.7 cells, respectively. In the presence of phytohemagglutinin-M, the IC50 on PBMCs proliferation was 4.42 mg/mL. The non-cytotoxic range of the extracts inhibited LPS-induced nitrite production in RAW264.7 cells with an IC50 value of 11.63 mg/mL. To determine the anti-oxidative properties, the N-acetyl cysteine equivalent antioxidant capacity of the extract was (32.62 ± 1.87) and (20.99 ± 2.79) mg N-acetyl cysteine/g extract, respectively determined by the ABTS-radical and DPPH-radical assay. However, the extract did not confer death protection in a hydrogen peroxide-induced RAW264.7 co-culturing model. Conclusions: Our study demonstrated the immunomodulation caused by the aqueous leaf extract of T. diversifolia, resulting from the inhibition of phytohemagglutinin-M-induced PBMCs proliferation and LPS-induced nitric oxide production in RAW264.7 macrophages. Although the anti-oxidative activity was presented in the chemical-based anti-oxidant assay, the extract cannot protect cell death from stress conditions.