A new pentacyclic phenol and other constituents from the root bark of Bauhinia racemosa Lamk.

Abstract

This work reported the isolation of one unknown (1) and 10 known compounds (2–11) from the root bark of Bauhinia racemosa Lamk. (family: Caesalpiniaceae). Racemosolone (1) was characterised as a pentacyclic phenolic compound possessing an unusual skeleton with a cycloheptane ring and a rare furopyran moiety. The structure elucidation was carried out on the basis of UV, infrared (IR), HR-ESI-MS, 1D and 2D NMR spectra and finally confirmed by the single crystal X-ray analysis. The known compounds were characterised as n-tetracosane, β-sitosteryl stearate, eicosanoic acid, stigmasterol, β-sitosterol, racemosol, octacosyl ferulate, de-O-methyl racemosol, lupeol and 1,7,8,12b-tetrahydro-2,2,4-trimethyl-2H-benzo[6,7]cyclohepta [1,2,3-de] [1] benzopyran-5,10,11 triol on the basis of spectroscopic data comparison with the literature value. Compounds with skeleton similar to 1 have never been reported from any natural or other source.

Keywords::

• Caesalpiniaceae
• Bauhinia racemosa Lamk.
• racemosolone
• pentacyclic phenol

Acknowledgements

The authors thank AIRF, Jawaharlal Nehru University, New Delhi, India for providing spectral data and to Dr Sheikh M. Mobin (IIT, Mumbai) for X-ray analysis. The authors (NY, TB) thank CSIR, New Delhi, India for financial assistance.