HPLC-HRMS-SPE-NMR analysis of bioactive fractions from Thunbergia laurifolia and Senegalia rugata leaves extracts and the effects on Nrf2, HMOX-1, NQO1, and CYP1A1 expressions

Abstract

Thunbergia laurifolia and Senegalia rugata leaves have been used as cancer prevention in Thai traditional medicine and showed promising chemopreventive effects in vitro in previous studies. However, the relevant mechanism and the active metabolites were still unknown. The objectives of this study are to investigate chemopreventive mechanisms, identify active fractions, and to provide information on their phytochemistry. The effects of the extracts on gene expressions of HepG2 cells were investigated using real-time PCR. High-resolution radical scavenging assay to identify active fractions was performed using ABTS^•+ reduction assay. Chemical characterization of the active fractions was then performed by HPLC-HRMS-SPE-NMR analysis. T.laurifolia leaves extract did not act via induction of NQO1, Nrf2, and HMOX-1 gene expressions. Rosmarinic acid could be the active metabolite. Mechanisms of S.rugata leaves extract might be due to the induction of Nrf2 expression. Three apigenin glucosides, including 3,6-di-C-glucosyl apigenin, isoschaftoside, and schaftoside, were reported in S.rugata for the first time and might contribute to the activity. In addition, the effect on CYP1A1 expression suggested that there was a low risk of DNA damage from both leave extracts.