Evaluation of anti-inflammatory and mechanism of action of extract of Macrosiphonia longiflora (Desf.) Müll. Arg

Ethnopharmacological relevance: Macrosiphonia longiflora (Desf.) Müll. Arg (Apocynaceae), popularly known as 'velame' and 'velame branco', is a native subshrub that grows in the Brazilian Cerrado. This plant is widely used in traditional medicine in the form of decoction and infusion, particularly as anti-inflammatory, depurative, anti-rheumatic, antisyphilitic and antiulcer remedy. There is no available information in the literature that has addressed its pharmacological activity and phytochemical analysis.

Aim of the study: This study aimed to evaluate the anti-inflammatory pharmacological profile of the hydroethanolic extract of Macrosiphonia longiflora, using in vivo and in vitro acute inflammation experimental models, as well as investigate the roles of cytokines and nitric oxide in its mechanism of action, and including phytochemical analysis constitution of its hydroethanolic extract.

Materials and methods: Hydroethanolic (70%) extract of Macrosiphonia longiflora (HEMl) was prepared by maceration. The preliminary phytochemical analysis was performed according to procedures described in the literature. Selected secondary metabolites detected were quantified by spectrophotometry and high performance liquid chromatography (HPLC). Its cytotoxic potential in Chinese hamster ovary (CHO-k1) epithelial cell lines was evaluated using Alamar Blue. in vivo anti-inflammatory activity was evaluated with carrageenan- and dextran-induced paw edemas, carrageenan-induced pleurisy in rats and lipopolysaccharide (LPS)-induced peritonitis in mice. The in vitro anti-inflammatory activity was evaluated using RAW 264.7 cells stimulated with LPS and interferon (INF)-γ. Effects of HEMl on the inflammatory cytokines (IL-1β, IL-10, IL-17, INF-γ and TNF-α) concentrations in the peritoneal lavage were evaluated using commercial ELISA kits, while the Griess method was employed to determine nitric oxide (NO) concentrations in the peritoneal lavage, as well as in the supernatants of RAW 264.7 cells.

Results: Preliminary phytochemical analysis, revealed the presence of phenolics compounds, terpenoids, alkaloids and flavonoids. Spectrophotometric analysis revealed the presence of relatively high content of phenolics and flavonoids in HEMl. HPLC analysis confirmed the presence of the quantified compounds and demonstrated the presence of ellagic acid in the detected matrix of compounds. HEMl appeared to be non-cytotoxic. It effectively inhibited (p<0.05) paw edema induced by carrageenan and dextran. Furthermore, HEMl also significantly reduced exudates volume and leukocyte migration in the carrageenan-induced pleurisy and LPS-induced peritonitis, neutrophils counts in LPS-induced peritonitis. HEMl also acts by effectively inhibiting the following inflammatory cytokines: IL-1β and IL-10 levels in the peritoneal lavage, but had no effect on IL-17 level in the peritonitis model. In addition, HEMl had no effect on the levels of tumor necrosis factor alpha (TNF-α) present in the peritoneal lavage and cells supernatants. The concentration of NO, as assessed by measurement of nitrite (NO2(-)), showed that pretreatment with HEMl reduced NO significantly in the peritoneal lavage and in RAW 264.7 cells co-stimulated with LPS and INF-γ.

Conclusion: The results obtained in this study indicate that HEMl possesses very low cytotoxic potential. In addition, it demonstrated a potent anti-inflammatory activity in both the in vivo and in vitro models of acute inflammation. The anti-inflammatory effect is partly related to the inhibition of IL-1β, IL-10, and nitric oxide releases, but independent of TNF-α and IL-17 modulation. Phytochemical analysis revealed the predominant presence of the flavonoids (naringin, rutin, myricetin, morin, quercetin, (±)-naringenin, and luteolin) and phenols (ellagic acid), which are possibly involved in the anti-inflammatory effect of HEMl. The current study provided supportive evidence for the popular use of HEMl in the treatment of inflammatory conditions, and shed more light on the possible roles of the inflammatory cytokines in its mechanisms of action as anti-inflammatory agent.