Nrf2-Mediated Antioxidant Activity of the inner bark extracts obtained from Tabebuia rosea (Bertol) DC and Tabebuia chrysantha (JACQ) G. Nicholson.

Abstract

Background: Several ethnobotanical and ethnopharmacological studies have shown the therapeutic potential of plants from the genus Tabebuia, which have long been used in traditional medicine in rural areas of South America, for the treatment of several human diseases. This study aimed to evaluate the Nrf2-mediated antioxidant activity of the inner bark extracts obtained from Tabebuia rosea and Tabebuia chrysantha. Methods: The antioxidant activity of extracts obtained from the inner bark of T. rosea and T. chrysantha was evaluated using the Oxygen radical absorbance capacity (ORAC) technique. The effect of extracts on the viability of HepG2 cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The translocation of Nrf2 to the nucleus after exposure of HepG2 cells to the extracts and controls (α-lipoic acid, curcumin and hydrogen peroxide) was evaluated using the Nrf2 transcription factor kit. Induction of the Nrf2-mediated antioxidant response gene (NQO1) was evaluated by real-time PCR. Results: The ethyl acetate extract obtained from both species displayed the highest ORAC activity (12,523 and 6,325 µmoles Eq Trolox/g extract, respectively). In addition, the extracts had the ability to activate and to translocate Nrf2 to the nucleus, as well as to induce the expression of NQO1. Conclusion: These results indicate that the ethyl acetate extracts obtained from the inner bark of T. chrysantha and T. rosea have an important antioxidant effect mediated by Nrf2 activation, and could be used as a new source of natural antioxidants.

Activation of the Keap1-Nrf2 pathway by specioside and the n-butanol extract from the inner bark of Tabebuia rosea (Bertol) DC

“…The results show how the compounds and extract increase the expression levels of HMOX-1 and NQO1. A study carried out by our research group evaluated the antioxidant capacity of the ethyl acetate extract from the inner barks of T. rosea and T chrysantha, in which the capacity of the extracts to activate Nrf2 translocation (after 4 hours of exposure) was reported to induce the expression of NQO1 21 . Glycosylated iridoid compounds such as aucubin 55 , catalposide and verproside (the main compounds found in the ethyl acetate fraction of Veronica ciliata) 56 showed a protective effect mediated by Nrf2, increasing the expression levels of the gene and the antioxidant protein NQO1.…”

“…Extracts were obtained as previously described 21,22 . Plant material was dried and macerated in analytical grade methanol for 48 hours.…”

“…mRNA was quantified with a NanoDrop 2000c (Thermo Fisher Scientific, Waltham, MA). The expression of the HMOX-1 and NQO1 genes 21,[39][40][41] was evaluated by RT-qPCR using predesigned TaqMan Gene Expression Assays (Hs01110250_m1 and Hs01045993_g1) and the TaqMan® RNA-to-CT TM Protective effects of the extract and compounds Hydrogen peroxide (H 2 O 2 ) was employed as a stressor agent in order to evaluate the protective capacity of the extract (0.25 and 1 µg/mL) and compounds (0.5 and 2 µM). The controls used were ALA and CUR, since these compounds have been reported to have protective effect against oxidative stress mediated by Nrf2 42,43 .…”

Activation of the Keap1-Nrf2 pathway by specioside and the n-butanol extract from the inner bark of Tabebuia rosea (Bertol) DC

“…Comparative analysis of the ethanolic extracts of T. rosea from extract from the inner barks of T. rosea and T chrysantha, in which the capacity of the extracts to activate Nrf2 translocation (after 4 hours of exposure) was reported to induce the expression of NQO1 21 . Glycosylated iridoid compounds such as aucubin 55 , catalposide and verproside (the main compounds found in the ethyl acetate fraction of Veronica ciliata) 56 showed a protective effect mediated by Nrf2, increasing the expression levels of the gene and the antioxidant In order to evaluate the protective effects of the extract and compounds, the concentration of H 2 O 2 (0.98 mM) that induced death by oxidative stress in 50% of the cells was determined.…”

Activation of the Keap1-Nrf2 pathway by specioside and the n-butanol extract from the inner bark of Tabebuia rosea (Bertol) DC

“…Extracts were obtained as previously described 21,22 . Plant material (2 Kg) was dried and macerated in analytical grade methanol for 48 hours.…”