Of cryptolepine

Fig. 5. HMQC spectrum of a 0.55 pmol sample of cryptolepine (1) dissolved in 30 pL d6-DMSO. The data were acquired in a 25.5 h experiment using a 1.7 mm gradient triple resonance submicro-NMR probe at 600 MHz. The minor correlation responses in the spectrum designated by arrows are an 8% ( 12pg) impurity of cryptolepine A-oxide present in the sample. All of the impurity responses were visible in a 12 h contour plot. Full HMBC data consistent with the structure were acquired for the impurity in 55 h. (Reprinted with permission from Ref. 12. Copyright 1998, American Chemical Society and American Society of Pharmacognosy.)...

Fig. 9. Proton NMR spectrum of a 75 ng (32 pmol) sample of cryptolepine (1) dissolved in 40 pL of 99.996% d6-DMSO. The data were acquired overnight using a prototype Varian proton Nano-probe with the sample spun at approximately 2 kHz. Both the residual water and protio-DMSO were irradiated to suppress their signals during the data acquisition. The suppressed DMSO signal is plotted on-scale for comparison to the 13C satellite lines from the solvent. Relative to the V-methyl group of the cryptolepine (1) ( 5.05ppm), the unsuppressed 13C satellite lines from the DMSO are observed with approximately twice the intensity of the Y-methyl signal. The line-labeled SSB is a spinning side band. (Reprinted with permission from Ref. 19. Copyright 2002, John Wiley Sons, Ltd.)...

Martin, G. E. and Williams, A. J. (March 11-16, 2001) Automated Structure Elucidation of Cryptolepine Derivatives, 42nd ENG, Orlando, EL. 

Cursory examination of the NMR sample, when dissolved in DMSO, allowed the deduction that an 11-cryptolepinyl moiety was contained in the structure based on the intense purple color, which is characteristic of the extended conjugation of cryptolepine. Because of the relatively small size of the sample, 100 pg, all of the NMR spectral data were recorded using a sealed sample of the degradant isolate in 150 pi of d -DMSO in a sealed 3 mm NMR tube using a 5 mm 500 MHz gradient inverse-detection triple resonance cryogenic NMR probe. 

Fig.(7). Structure of Strychnos monoindole alkaloids evaluated for their anticancer and/or antiprotozoal acrtivites. Structure of cryptolepine and ellipticine are given for comparison purpose.

Greller, P., et al. "Antimalarial Activity of Cryptolepine and Isocryptolepine, Alkaloids Isolated from Cryptolepsis sanguinolenta." Phytother Res 10(4) 317321, 1996. Abstract. 

Our study of cryptolepine, performed on 5 mg of material dissolved in 0.8 ml of DMSO-d6, highlights what will probably become an increasingly common protocol as inverse-detected 2D NMR methods become more widely implemented. Typically, we acquire a proton reference spectrum followed by COSY and HMQC spectra. On the sample in question here. 

Practically, SIMBA spectra of C5a and C4a confirmed the correlation from the N-methyl resonance that was excluded from the F2 spectral window, in about 10 min. A series of SIMBA spectra using a range of five optima were also acquired for the ClOa resonance did not exhibit a Jch correlation to the Hll resonance of cryptolepine. Unfortunately, the SIMBA spectra likewise failed to confirm this correlation pathway, but allowed the complete study to be undertaken in less than one half hour. Acquisition of the corresponding set of HMBC spectra to look for the connectivity from Hll—>C10a would have been time prohibitive. 

Ablordeppy SY, Hufford CD, Bourne RF, Dwuma-Badu D (1990) Proton NMR and carbon-13 NMR assignments of cryptolepine, a 3 4-benzo-d-carboline derivative isolated from Cryptolepis sanguinolenta. Planta Med 56 416-417 Alam M, Mroue M (1991) Crooksiine, a bisindole alkaloid from Haplophyton crooksii. Phytochemistry 30 1741-1744... 

The latter alkaloid is a violet base obtained from Cryptolepis species (Asclepiadaceae) which with selenium gave quindoline which had already been prepared 45 years before. An efficient biogenetic type synthesis of cryptolepine was from indoxyl and o-methylamino benzaldehyde in weakly acidic medium. 

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