A review of:
High-Speed Extraction and HPLC Fingerprinting of Medicinal Plants –
II. Application to Harman Alkaloids of Genus Passiflora
E.A.Abourashed, J.Vanderplank and I.A.Khan
Pharmaceutical Biology, 41(2), 100-106 (2003)
The previous article in this series [1], discussing the measurement of flavonoids in
Passiflora, was reviewed in Passiflorunde, 11(1), 25-26 (2003). This second report by
the same authors describes the quantitative analysis of harman alkaloids in almost 100
species and several hybrids in the genus Passiflora using high-performance liquid
chromatography. Data are presented for the concentration of five alkaloids: harmalol,
harmol, harmane, harmaline and harmine. These substances are well-known as
monoamine oxidase inhibitors that have a number of effects on the central nervous
system (CNS). As in the earlier study, the objective was partly to explore the chemical
basis for the properties of the medicinally significant P. incarnata L.
One or more of the above five harman alkaloids was detected in over half of the
samples examined, but in a large number of cases they were present at concentrations
just above the limit of detection and below the limit of quantification. The most
commonly-found marker was harmine, but harmol was detected in only eleven
samples and harmalol in just four. The authors accept that at such low levels, it is
unlikely that harman alkaloids would be considered as reliable chemotaxonomic
markers for the genus Passiflora. No clear pattern emerged from either the qualitative
or quantitative results to suggest any link with even the major subsections of the
genus. Furthermore, and as with the flavonoids, it was not clear to what extent the
presence and amounts of harman alkaloids were determined by genetic factors or what
role was played by environmental factors. Thus, two samples of P. macrophylla
MAST. had quite different profiles, as did two samples of P. caerulea L., two samples
of P. edulis SIMS and two samples of P. alata CURTIS. Although the profile of
P. foetida L. var. gossipifolia was very different from those of three other samples of
P. foetida, it could be argued that different genotypes were involved. The authors
acknowledge that seasonal and other variations could affect the qualitative and
quantitative data and thereby hinder comparison between samples. A useful extension
of this and the authors’ previous work would therefore be to explore the intra-species
variation in harman alkaloids and flavonoids. There were insufficient data to
determine if the alkaloid profiles of any of the hybrids tested could be matched
against the parent species. Although the profile of P. ‘St Rule’ and P. gibertii were
different, this result sheds little light on whether they are one and the same.
It is doubtful whether any of these harman alkaloids could have any pharmacological
importance in Passiflora, and the authors conclude by recognising that the nature of
the compounds responsible for the CNS activity of P. incarnata remains an open
question. There were several minor errors in nomenclature such as “×violaceae”,
“amethystine” and “×exconiensis”.
Reference
[1]
E.A.Abourashed, J.R.Vanderplank and I.A.Khan, High-Speed Extraction and
HPLC Fingerprinting of Medicinal Plants – I. Application to Passiflora
Flavonoids, Pharmaceutical Biology, 40(2), 81-91 (2002)
L.A. King
8 February 2004
German translation by E. Kugler published in Passiflounde 12(3), 19-20 (2004)