SUBMICROMOLE STRUCTURE ELUCIDATION - CRYPTOLEPICARBOLINE - A NOVEL DIMERIC ALKALOID FROM CRYPTOLEPIS-SANGUINOLENTA

Cryptolepis sanguinolenta (Lindl.) Schlechter (Asclepiadaceae), a shru b indigenous to West Africa, has been employed by traditional healers in the treatment of various fevers, including malaria, Column chromato graphy of the alkaloid fraction obtained from a defatted ethanolic ext ract of the roots of the plant afforded the previously characterized a lkaloids cryptolepine, quindoline and cryptospirolepine. Continued ext ensive column chromatography, followed by preparative high-performance liquid chromatography, resulted in the isolation of nine new alkaloid s, including approximately 100 mu g of a novel indoloquinoline-beta-ca rboline dimeric alkaloid, cryptolepicarboline. The structure was eluci dated through the use of a combination of spectroscopic techniques whi ch included UV, Fourier transform, electron impact mass spectrometry, and 500 MHz NMR spectroscopy. NMR data included 1D H-1 and C-13 refere nce spectra, the latter recorded in 40 mu l of DMSO-d(6) using a new V arian heteronuclear Nano-probe and in 140 mu l of DMSO-d(6) using a Na lorac carbon-optimized microprobe. These C-13 NMR spectra allow the fi rst direct comparison of these two probe formats. Homonuclear 2D NMR d ata acquired included both COSY and ROESY spectra. The homonuclear 2D experiments were variously performed in both a homonuclear Nano-probe and micro-inverse detection probes. Heteronuclear shift correlation ex periments included HMQC, HMBC and IDR (inverted direct response)-HMQC- TOCSY spectra, which were uniformly performed using a 500 MHz Nalorac micro inverse-detection probe.