Flavonoids isolated from Sida santaremnensis H. Monteiro (“Guanxuma”) and evaluation of biological activities

Introduction: Sida santaremnensis H. Monteiro (Malvaceae) is a plant popularly known as "vassourinha" or "guanxuma" that has been described as vasorelaxant, antiulcerogenic, antinociceptive and antiedematogenic. Objective: To contribute with the phytochemical and pharmacological profile of Sida santaremnensis through the isolation, purification and determination of chemical constituents of this plant, as well as through the evaluation of the anti-inflammatory and antitumor activity and leishmanicidal effect of the isolated constituent in a greater amount. Methods: The isolation of substances from the plant herein studied was performed with column chromatographic and analytical thin-layer methods and structural determination made by spectroscopic methods, such as Nuclear Magnetic Resonance, Hydrogen and Carbon 13, and comparisons with data from the literature. To assess pharmacological activities, cell viability tests, determination of nitric oxide levels, leishmanicidal activity, among others, were performed. Results: Two flavonoids from S. santaremnensis were obtained, kaempferol (S-1) and kaepferol 3-O-β-D-glycosyl-6’’-α-L-rhamnoside (S-2), the latter in a greater amount. The evaluation of the antitumor activity of the glycosylated flavonoid demonstrated that it does not present hemolytic activity against the human promyelocytic leukemia cell line (HL-60), and that it presented weak leishmanicidal activity. The immunopharmacological evaluation of kaempferol 3-O-β-D-glucosyl-6’’-α-L-rhamnoside revealed that it presents a possible anti-inflammatory action related to the inhibition of the production of nitrite by LPS-stimulated macrophages. Conclusion: These data demonstrate that kaempferol 3-O-β-D-glucosyl-6’’-α-L-rhamnoside has low toxicity, in addition to antileishmania, anti-inflammatory and immunomodulatory properties, which makes it a therapeutic potential for infectious and inflammatory diseases mediated by macrophages.