ABSTRACT
One new iridoid named aureanin (1) was isolated from the leaves of Tabebuia aurea (Silva Manso) Benth. & Hook.f. ex S.Moore, together with eight known compounds, isoquercetin (2), astragalin (3), callicoside B (4), amphipaniculoside E (5), rehmaglutin D (6), quercetin-3-sambubioside (7), rutin (8), kaempferol-3-O-rutinoside (9). The structures of the isolated compounds were elucidated and confirmed by spectroscopic methods, including 1 D and 2 D NMR experiments, as well as HR-ESI-MS. Compounds 1-9 were evaluated for their in vitro cytotoxic activity against three human cancer cell lines (A549, HepG2, and MCF-7) and Leishmania major. Compound 4 showed activity against A549 (IC50: 36.8 ± 1.5 µg/mL, etoposide (positive control): 28.1 ± 4.2 µg/mL), however, none of the compounds were active against L. major.
ABSTRACT
The bioactivity-guided fractionation of the total ethanolic extract of the leaves of Tabebuia aurea revealed the cytotoxic and antileishmanial potency of the ethyl acetate fraction, in which its phytochemical investigation resulted in the isolation of five triterpenes; identified as oleanolic acid (1), ursolic acid (2), pomolic acid (3), tormentic acid (4), 3ß,6ß,19α-trihydroxy-urs-12-en-28-oic acid (5) in addition to one triterpenoid glucoside, spathodic acid 28-O-ß-D-glucopyranoside (6). Whereas compound 1 showed cytotoxic activity against three different cell lines; A549, MCF-7 and HepG2 with IC50 values of 31.7 ± 1.2, 27.4 ± 1.8 and 28.8 ± 1.1 µg/mL, respectively (etoposide as a positive control: 28.1 ± 4.2, 22.5 ± 4.5, and 20.4 ± 0.8 µg/mL, respectively), while compounds 1 and 2 showed antileishmanial activity with IC50 values of 10.2 ± 0.9 µg/mL and 5.1 ± 0.4 µg/mL, respectively (miltefosine: 7.7 ± 2.1 µg/mL).
