T.A. van Beek

Tabernaemontana L. (Apocynaceae): A review of its taxonomy, phytochemistry, ethnobotany and pharmacology☆

The taxonomy, phytochemistry, ethnobotany, and pharmacology of the genus Tabernaemontana L. (Apocynaceae) is reviewed. The genus is currently being revised taxonomically; most of the segregate genera are being reunited with it and the number of species that will ultimately be recognized will probably be about 100. All the names encountered in the chemical and ethnobotanical literature have been evaluated as far as possible, and a list is presented of the recognized species and their synonyms. The biogenesis and classification of the indole alkaloids found in Tabernaemontana species is set out and some problems in the determination of their stereochemistry are discussed. To facilitate access to the information, three lists have been compiled: the alkaloids in alphabetical order; the alkaloids in order of increasing molecular weight; and the alkaloids grouped according to their biogenetic classification, together with the species and plant part(s) in which they are known to occur. Biogenetic and chemotaxonomic aspects are briefly considered. A table of the non-alkaloidal constituents is also included. The ethnobotany of individual Tabernaemontana species is outlined and an overall assessment made. Likewise, information on the pharmacology of crude extracts and individual alkaloids from Tabernaemontana species has been assembled and appraised.

DETERMINATION OF GINKGOLIDES AND BILOBALIDE IN GINKGO-BILOBA LEAVES AND PHYTOPHARMACEUTICALS

Abstract A method has been developed for the determination of the pharmacologically active terpenoids ginkgolide A, B and C and bilobalide in Ginkgo biloba leaves and phytopharmaceutical preparations containing ginkgo extracts. The leaves (400–800 mg) ar selectively extracted with methanol—water (10:90) and the resulting extract is purified by means of a polyamide and a C 18 solid-phase extraction column After concentration, the terpenoids are determined by high-performance liquid chromatography on a C 18 column with methanol—water (33:67) as eluent and refractive index detection. Benzyl alcohol is used as an internal standard. The recovery of the method is 95 ± 5%. The reproducibility is dependent on the concentration and varies from 2 to 15%. The minimum concentraon that can be determined in leaves is 10 μg of terpenoid/g of dry leaves. With a small modification the method can be used equally well for phytopharmaceuticals. Several ginkgo medicines were investigated and the total concentration of terpenoids was found to vary by a factor 18. The concentration in leaves varied by a factor 40.

Screening of the needles of different yew species and cultivars for paclitaxel and related taxoids

The needles of several yew species and cultivars were analysed by high-pressure liquid chromatography for paclitaxel, 10-deacetylpaclitaxel, cephalomannine, baccatin III, 10-deacetylbaccatin III and brevifoliol. About 750 samples were collected from five different locations in the Netherlands and the UK. The results of this screening show a large variation in taxane content between the different species and cultivars. The content of paclitaxel and 10-deacetylbaccatin III varied from 0 to 500 micrograms/g and 0 to 4800 micrograms/g dried needles, respectively. Brevifoliol was found in a very high concentration in Taxus brevifolia. 10-Deacetylpaclitaxel, cephalomannine and baccatin III were found in concentrations ranging from 0 to 500 micrograms/g dried needles.

Essential oil of Amyris balsamifera.

Abstract The essential oil composition of Amyris balsamifera was investigated by GC-MS. Major constituents were separated by fractional distillation and various chromatographic techniques, and identified by mass, 1H and 13C NMR spectroscopy and/or chemical reactions. The oil consisted of 17.5% sesquiterpene hydrocarbons and 82.5% oxygenated sesquiterpenes. Major compounds were β-sesquiphellandrene, elemol, 10-epi-γ-eudesmol, γ-eudesmol, valerianol, α-eudesmol, 7-epi-α-eudesmol and β-eudesmol. 7-epi-α-Eudesmol is reported for the first time as a natural product.

Screening of antimicrobial activity of some plants belonging to the Apocynaceae and Loganiaceae

A review is given of the literature on the antimicrobial activity of various indole alkaloids. The data are briefly discussed. A screening was performed of a series of plants belonging to the indole alkaloid rich plant families Apocynaceae and Loganiaceae, 25 materials representing 14 Apocynaceae species and 54 materials representing 41 Strychnos species were investigated. No activity against the yeast or the fungus, used as test organisms was found. A number of extracts showed activity against the gram-positive test organisms, 4 species showed activity against gram-negative bacteria.

Antimicrobially active alkaloids from Tabernaemontana pachysiphon

Abstract Twenty-three alkaloids and five steroids and triterpenes have been isolated and identified from the root bark and stem bark of a Nigerian Tabernaemontana pachysiphon . The following bases have not previously been obtained from this species: isositsirikine, 16-epiisositsirikine, normacusine B, 16-epiaffinine, anhydrovobasindiol, tubotaiwine, ibogaline, isovoacangine, voacamine, lochnericine, 3 R -hydroxyconopharyngine, 3 S -hydroxyconopharyngine and 11-demethylconoduramine, the last three being new alkaloids. The dimeric indole alkaloids and 3 R/S -hydroxyconopharyngine were shown to possess strong antibacterial activity against Gram-positive bacteria and the dimers against Gram-negative bacteria also.

Distribution of ginkgolides and terpenoid biosynthetic activity in Ginkgo biloba

Abstract The terpene trilactone content (bilobalide and ginkgolides) of extracts prepared from leaves of terminal buds, rosettes and side branches, from stem and root bark, and from root and root meristems of three-year-old Ginkgo biloba plants was determined. The aerial parts were relatively rich in bilobalide while ginkgolides were the major constituents of the underground parts. The formation of farnesyl and geranylgeranyl pyrophosphate was monitored by incubating cell-free extracts prepared from the corresponding plant parts with [1-14C]isopentenyl pyrophosphate. Extracts prepared from leaves of the terminal buds displayed terpenoid biosynthetic activity, suggesting that terpene trilactone synthesis might occur in actively growing tissues.

Chemotaxonomy of Taxus

A chemotaxonomical study of the genus Taxus was undertaken, based on the concentration of six neutral taxanes in its needles. A total of 750 different samples from 10 different Taxus species or hybrids were analysed. The chemical data were processed by Cluster and Principal Component Analysis. The results of the chemical analyses allowed the distinction of a North American and a Eurasian group of species. Cultivars belonging to the closely related species T. baccata, T. cuspidata and T. x media could be divided in five major groups based on morphological data. However, a classification of these same cultivars based on the chemical data showed no correlation between taxane content and morphology. The chemical dataset showed some separation of the species T. baccata, T. cuspidata and T. x media, but did not indicate an intermediate position for T. x media, but rather a heterosis effect for the hybrids.

Production of ginkgolide and bilobalide in transformed and gametophyte derived cell cultures of Ginkgo biloba

Abstract Ginkgolide and bilobalide were detected by HPLC analysis in cell cultures established from various G. biloba explants. These secondary metabolites of pharmacological interest were found to occur in concentrations of 0.065 and 0.087% (dry weight) in two cell suspensions. One was derived from a female prothallus and the other one from putatively transformed embryos, by transfection via Agrobacterium rhizogenes agropine type strain CFBP 2409 (A4).

Investigation of the essential oil of Vietnamese ginger.

Abstract The composition of the hydrodistilled essential oil of dried Vietnamese ginger was determined by means of GC, GC-MS and 13C NMR. The oil yield was