Antioxidant Constituents from the Stem and Leaf of Helicteres hirsuta Loureiro

Background: Helicteres hirsuta has been used traditionally as a useful agent for hepatoprotective treatment. The aim of the current study is to isolate chemical constituents from the EtOAc extract of H. hirsuta stem and evaluate the capacity of the isolated compounds against hydroperoxide damaged rat liver cells. Methods: Column chromatography was used for phytochemical isolation whereas MTT method was applied for intracellular antioxidative assay. Results: Phytochemical analysis of the EtOAc extract of H. hirsuta stem led to the isolation and determination of four triterpenoids betulin (1), bentulinic acid (2), alphitolic acid (3), and oleanolic acid (4), together with two steroids stigmast-4-ene-6β-ol-3-one (5), and β-sitostenone (6), whereas EtOAc extract of its leaf was composed of three steroids cucurbitacin D (11), cucurbitacin I (12), and simiarenol (13), four flavonoids tiliroside (14), potengriffioside A (15), kaempferide (16), and isokaempferide (17), along with two carotenoids lutelin (18), and β-carotene (19). Isolated compounds 3, 5, 6, 16, and 17 were found in genus Helicteres for the first time, while carotenoids 18, and 19 were never isolated from family Sterculiaceae before. Phytochemicals derived H. hirsuta species are also useful agents for antioxidative drugs, e.g, flavonol 17 induced the significant EC50 value of 22.24 ± 0.14 μg/mL, as compared with that of positive control curcumin (EC50 19.33 ± 0.77 μg/mL), against hydroperoxide damaged rat liver cells. Conclusion: Antioxidative activity of the EtOAc extract of H. hirsuta stem against hydroperoxide is mostly based on the role of flavonoids.