Chemical constituents and NAD(P)H: Quinone oxidoreductase 1 (NQO1) inducer activity of Teucrium oliverianum Ging. ex Benth

The aqueous methanolic extract of Teucrium oliverianum was partitioned with different solvent systems with increasing polarities. The phytochemical investigation of the CHCl₃ fraction led to the isolation of six compounds. The structures of the compounds were determined by NMR co-chromatographic TLC and found to be: 8-O-acetylharpagide 1, 12-O-methylteucrolin A 2, teucrolivin A 3, eupatorin 4, teucrolivin B 5 and 24 (S)-stigmasta-5, 22, 25-trin-3β-ol 6. The total extract and the isolated compounds were tested for their ability to induce the cytoprotective enzyme NAD (P)H:quinone oxidoreductase (NQO1). Among the purified compounds, the diterpenoid, teucrolivin B 5 was the only one which was able to induce NQO1 by more than 2-fold, whereas the flavonoid eupatorin 4 was the most potent inducer, increasing the NQO1 specific activity by 1.75-fold at a concentration of 25 μg/ml. Compounds 2, 3 and 6 were essentially inactive, indicating that compounds 1, 4 and 5 are the main contributors to the NQO1 inducer activity of the total extract.