Triterpenes and phenolic compounds isolated from the aerial parts of Herissantia tiubae and evaluation of 5,4′,-dihydroxy-3,6,7,8,3′-pentamethoxyflavone as a modulator of bacterial drug resistance

Abstract

In our continuous study of the Malvaceae family, we describe here the isolation of four triterpenes (frideline, lupeol, cycloartenol, and cycloeucalenol), a steroid (β-sitosterol), and four phenolic compounds from the aerial parts of Herissantia tiubae (K. Schum.) Brizicky (i.e., a benzoic acid derivative, a coumarin and two flavonoids, kaempferol 7-O-α-l-rhamnopyranoside and 4′,5-dihydroxy-3,6,7,8,3′-pentamethoxyflavone). The structural identification of the compounds was made by comparison with literature data and spectral analysis, including two-dimensional NMR techniques. These compounds are reported here for the first time in genus Herissantia. The pentamethoxyflavone was assayed against strains of Staphylococcus aureus possessing efflux mechanisms of resistance to norfloxacin, tetracycline, and erythromycin. Although the compound did not display relevant antibacterial activity (MIC ≥ 512 μg/mL), it modulated the activity of antibiotics, i.e., in combination with antibiotics (at 128 μg/mL), a two-fold reduction in the MIC values for tetracycline and erythromycin, a 32-fold reduction in the MIC for norfloxacin were observed.

Keywords::

• Malvaceae
• flavonoids
• antibacterial activity

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Acknowledgements

J.P.S-J. and V.S.F-S. are very grateful to Dr. Simon Gibbons (University of London) for his valuable and kind cooperation. CNPq (PIBIC/UFPb) is thanked for the award of an undergraduate studentship. This work was supported by the following Brazilian agencies: CNPq and CAPES.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.