rifampin and tryptanthrine

A series of Wrightia hanleyi extracts was screened for activity against Mycobacterium tuberculosis H37Rv. One active fraction contained a compound that initially appeared to be either the isoflavonoid wrightiadione or the alkaloid tryptanthrin, both of which have been previously reported in other Wrightia species. Characterization by NMR and MS, as well as evaluation of the literature describing these compounds, led to the conclusion that wrightiadione (1) was misidentified in the first report of its isolation from W. tomentosa in 1992 and again in 2015 when reported in W. pubescens and W. religiosa. Instead, the molecule described in these reports and in the present work is almost certainly the isobaric (same nominal mass) and isosteric (same number of atoms, valency, and shape) tryptanthrin (2), a well-known quinazolinone alkaloid found in a variety of plants including Wrightia species. Tryptanthrin (2) is also accessible synthetically via several routes and has been thoroughly characterized. Wrightiadione (1) has been synthesized and characterized and may have useful biological activity; however, this compound can no longer be said to be known to exist in Nature. To our knowledge, this misidentification of wrightiadione (1) has heretofore been unrecognized.

Topics: Antitubercular Agents; Apocynaceae; Carbon-13 Magnetic Resonance Spectroscopy; Isoflavones; Mass Spectrometry; Microbial Sensitivity Tests; Molecular Structure; Mycobacterium tuberculosis; Proton Magnetic Resonance Spectroscopy; Quinazolines

The natural product tryptanthrin (1a) represents a potential lead for new tuberculosis (TB) drugs since tryptanthrin and its synthetic analogues possess potent in vitro activity against Mycobacterium tuberculosis (Mtb). However, in spite of their in vitro activity, none of these agents have been shown to be efficacious in vivo against animal models of TB. Described herein are syntheses of new tryptanthrin analogues together with a systematic investigation of their in vitro antitubercular activity and ADME properties followed by pharmacokinetic characterization in rodents for the most promising compounds. Those with the best potency and oral bioavailability were progressed to evaluations of efficacy against acute murine TB. The work aimed to prove the concept that this compound class can limit growth of Mtb during infection as well as to establish the SAR for in vitro activity against Mtb and the range of in vitro ADME parameters for this class of natural products. Novel C-11-deoxy (5b) and A-ring-saturated (6) tryptanthrin analogues were discovered that maintained activity against Mtb and showed improved solubility compared to tryptanthrin as well as evidence of oral bioavailability in rodents. However, neither 5b nor 6 demonstrated efficacy against acute murine TB following administration at doses up to 400 mg/kg daily for 4 weeks. Although 5b and 6 failed to inhibit replication or kill Mtb in vivo, they illuminate a path to new structural variations of the tryptanthrin scaffold that may maximize the potential of this class of compounds against TB.

Topics: Animals; Antitubercular Agents; Cytochrome P-450 Enzyme System; Drug Design; Humans; Mice; Mice, Inbred C57BL; Microbial Sensitivity Tests; Molecular Structure; Mycobacterium tuberculosis; Quinazolines; Rats; Structure-Activity Relationship; Tuberculosis