An iboga alkaloid chemotaxonomic marker from endemic Tabernaemontana ternifolia with antitubercular activity

Abstract

Coronaridine (1) was isolated from the CH₂Cl₂ root extract of Tabernaemontana ternifolia. The structure of 1 was established from 1D- and 2D-NMR and HR-ESIMS experiments, and by comparison with reported spectroscopic data. To date, this is the first report of compound 1 from T. ternifolia, introduced as new Tabernaemontana species from Philippines in 2005 on the basis of morphological characters. Coronaridine, an iboga-type indole alkaloid, has been isolated from over 50 Tabernaemontana species and can thus be inferred as a chemotaxonomic marker of the genus. T. ternifolia has a distinct arrangement of leaves not known in the genus, but is variable in other genera. Its isolation from endemic T. ternifolia establishes its position in the genus and supports the claim that coronaridine is a chemical marker of the genus Tabernaemontana. Interestingly, coronaridine exhibited relatively weak activity against Mycobacterium tuberculosis H₃₇Rv (MIC 82.64 μg/mL) (Rifampicin MIC 0.05 μg/mL).

Graphical Abstract

Keywords:

• Tabernaemontana ternifolia
• endemic
• Apocynaceae
• coronaridine
• syringaldehyde
• Mycobacterium tuberculosis

Acknowledgments

RCG acknowledges the DOST-SEI ASTHRDP and the CHED-FDP for the Ph.D. research grants; the Palawan Council for Sustainable Development for permitting plant collection in a protected area; and Prof. Norman G. Lewis for allowing the final stages of compound purification to be conducted at the Institute of Biological Chemistry, Washington State University. It is also acknowledged that a portion of this research was performed using EMSL, a U.S. DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research.

Disclosure statement

No potential conflict of interest was reported by the authors.