Cyanohydrin glycosides of Passiflora: distribution pattern, a saturated cyclopentane derivative from P. guatemalensis, and formation of pseudocyanogenic alpha-hydroxyamides as isolation artefacts

Nineteen species of Passiflora (Passifloraceae) were examined for the presence of cyanogenic glycosides. Passibiflorin, a bisglycoside containing the 6-deoxy-beta-D-gulopyranosyl residue, was isolated from P. apetala, P. biflora, P. cuneata, P. indecora, P. murucuja and P. perfoliata. In some cases this glycoside co-occurs with simple beta-D-glucopyranosides: tetraphyllin A, deidaclin, tetraphyllin B, volkenin, epivolkenin and taraktophyllin. P. citrina contains passicapsin, a rare glycoside with the 2,6-dideoxy-beta-D-xylo-hexopyranosyl moiety, while P. herbertiana contains tetraphyllin A, deidaclin, epivolkenin and taraktophyllin, P. discophora tetraphyllin B and volkenin, and P. x violacea tetraphyllin B sulfate. The remaining species were noncyanogenic. The glycosides were identified by 1H and 13C NMR spectroscopy following isolation by reversed-phase preparative HPLC. From P. guatemalensis, a new glucoside named passiguatemalin was isolated and identified as a 1-(beta-D-glucopyranosyloxy)-2,3-dihydroxycyclopentane-1-carbonitrile. An isomeric glycoside was prepared by catalytic hydrogenation of gynocardin. alpha-Hydroxyamides corresponding to the cyanogenic glycosides were isolated from several Passiflora species. These alpha-hydroxyamides, presumably formed during processing of the plant material, behave as cyanogenic compounds when treated with commercial Helix pomatia crude enzyme preparation. Thus, the enzyme preparation appears to contain an amide dehydratase, which converts alpha-hydroxyamides to cyanohydrins that liberate cyanide; this finding is of interest in connection with analysis of plant tissues and extracts using Helix pomatia enzymes.