P. H. Amvam Zollo

Aromatic plants of Tropical Central Africa. Part XXXII. Chemical composition and antifungal activity of thirteen essential oils from aromatic plants of Cameroon

The essential oils of Hoslundia opposita Vahl. (leaves), Hyptis lanceolata Poit. (whole plant), Hyptis suaveolens Poit. (leaves), Ocimum basilicum L. (whole plant), Ocimum canum Sim. (whole plant), Ocimum gratissimum L. (leaves), Plectranthus glandulosus Hook (leaves), Thymus vulgaris L. (whole plant), Piper capense L. (leaves and seeds), Piper guineense Schum. et Thom. (leaves and seeds) and Bixa orellana L. (leaves) which were obtained by hydrodistillation from plants collected in different regions of Cameroon, were analysed by GC and combined GC–MS. The oils of Hoslundia opposita, Hyptis lanceolata, H. suaveolens, T. vulgaris, P. capense, P. guineense and B. orellana were found to be rich in hydrocarbons (>58%). The most abundant compounds in the oils of O. basilicum, O. canum and P. glandulosus were alcohols and oxides (>40%), while in the oil of O. gratissimum the amounts of hydrocarbons and oxygen-containing components were roughly the same. It is of interest to note the presence in O. basilicum and P. guineense (leaves) of aromatic compounds in a sizeable amount (13.5% and 25.6% respectively). The antifungal activity of these essential oils against Candida albicans, Cryptococcus neoformans, Aspergillus flavus, Aureobasidium pullulans, Microsporum gypseum, Trichophyton rubrum, and Trichoderma viride were also investigated. Two methods were used for these antifungal tests: the microatmosphere method and the standardized broth dilution micromethod. Three oils (from Ocimum gratissimum, Thymus vulgaris and Ocimum basilicum) showed strong antifungal activity.

Evaluation of antifungal activity of extracts of two Cameroonian Rutaceae: Zanthoxylum leprieurii Guill. et Perr. and Zanthoxylum xanthoxyloides Waterm.

Aqueous-ethanol 90% extracts of leaves, roots and stem barks of Zanthoxylum leprieurii and Zanthoxylum xanthoxyloides were examined for their antifungal properties against nine fungi by dilution methods on a solid medium and in a liquid medium. Our results indicate that these extracts, to varying extents, inhibit the in vitro growth of Candida albicans, Cryptococcus neoformans and seven filamentous fungi tested. Only the extracts obtained from the roots and stem barks of Z. xanthoxyloides showed antifungal activity on the germs studied, with minimal inhibitory concentration varying, respectively, from 0.5 to 1 mg/ml for the roots and from 0.125 to 1 mg/ml for the stem barks.

Variability in the Chemical Compositions of the Essential Oils of Five Ocimum Species from Tropical African Area

Abstract As part of our research on aromatic plants from Africa, we have analyzed, via GC and CG/MS, the essential oils from fresh leaves of five Ocimum species from tropical Africa: Ocimum basilicum L., O. gratissimum L., O. americanum L. (syn: O. canum Sims), O. lamiifolium Hochst. ex Benth. and O. minimum L. The chemical compositions of O. basilicum, O. gratissimum and O. minimum essential oils could be related to some chemotypes already defined for these three species: linalool- or methyl chavicol-types for the first species, thymol- or eugenol- or ocimenes/far- nesenes-types for the second one; finally, a high content of methyl chavicol (34.3%) and linalool (17.8%) was found in O. minimum oil, similar to that already described for a Brazilian species. On the other hand, an essential oil dominated by 1,8-cineole was described for the first time for a sample of O. americanum. Finally, the oil of O. lamiifolium, which was rich in sabinene, is chemically described for the first time.

Antifungal activity of Piper guineense of Cameroon.

The antifungal activity of the ethanol extract of the seeds of Piper guineense and some of its fractions obtained by column chromatography was investigated using filamentous fungi and yeasts. The results indicated a significant antifungal effect. No toxic effect was observed in mice treated per os with the extract.

Aromatic plants of tropical Central Africa. Part XXXI. Tricyclic sesquiterpenes from the root essential oil of Echinops giganteus var. lelyi C. D. Adams

The essential oil from the roots of Echinops giganteus var. lelyi C. D. Adams from Cameroon was investigated by GC, GC-MS and NMR spectroscopy. The oil contains exclusively sesquiterpenes, two-thirds of which are hydrocarbons. Eighteen components, representing 83% of the oil, could be identified; 14 of them (80%) are tricyclic sesquiterpenes with presilphiperfolane, silphiperfolane, isocomane and modhephane skeletons. The main constituent is silphiperfol-6-ene (26.9%), accompanied by presilphiperfol-7(8)-ene (9.4%) which is found for the first time as a natural product. Only one of the four silphiperfolan-6-ol stereoisomers I-IV detected has been described previously. All constituents identified seem to be generated by the same biogenetic pathway.

Antifungal Activity of Chromolaena odorata (L.) King & Robinson(Asteraceae) of Cameroon

An aqueous ethanol extract of leaves of Chromolaena odorata and some of its fractions were examined for their antifungal properties by dilution methods on solid and liquid media, using yeasts and filamentous fungi. Extract and fractions inhibit the in vitro growth of Cryptococcus neoformans, Microsporum gypseum, Trichophyton mentagrophytes and Trichophyton rubrum with a minimal inhibitory concentration range from 62.5 to 500 µg/ml for the extract and from 25 to 100 µg/ml for fractions. A qualitative chemical analysis of the extract and fractions showed the presence of biologically active constituents such as some coumarins, flavonoids, phenols, tannins and sterols. No toxic effect was observed in mice treated per os with the extract. This study provides a scientific confirmation of the use of Chromolaena odorata in traditional medicine.

Aromatic plants of Tropical Central Africa. Part XXVII.Comparative Study of the Volatile Constituents of Five Annonaceae Species Growing in Cameroon

Nine essential oils were isolated from five Annonaceae species growing in Cameroon. The samples were analysed by GC and GC-MS. The volatile oils obtained from seeds of Monodora myristica (Gaertn.) Dunal and Monodora brevipes Benth., those from leaves and fruits of Annona senegalensis. Pers. var. senegalensis and that from fruits of Cananga odorata (Lam.) Hook. Fil. et Thoms. were mainly monoterpenic, the major components being α-phellandrene or sabinene and mycrene. The leaf essential oil of M. brevipes contained approximately equal amounts of monoterpenes and sesquiterpenes, with two major components with an acyclic structure: (Z)-β- ocimene and (E),(E) α-farnesene. Finally, the oils from leaves of M. myristica, Annona muricata L. and C. odorata contained mostly sesquiterpenes, the major constituent being β-caryophyllene.

Composition of the essential oils from the leaves of two varieties of Aspilia africana (Pers.) C. D. Adams from Cameroon

Four essential oil samples obtained by hydrodistillation from the leaves of Aspilia africana var. africana and a corresponding sample of A. africana var. ambigua were analysed by GC and GC–MS. The two varieties were poor in essential oil content (<0.1%). The qualitative composition of the essential oils was found to be quite similar, irrespective of the area and date of plant collection. Marked differences were, however, observed in the quantitative composition of the oils from the two varieties. As far as A. africana var. africana is concerned, two oil samples from Bafoussam were rich in sesquiterpenes (88% and 94%) with germacrene-D (45% and 54%) as the major component, while two oil samples from Yaounde contained mainly monoterpenes (63% and 48%) with α-pinene (39% and 27%) as the most abundant component. The variety A. africana var. ambigua afforded an essential oil rich in monoterpenes (54%) with limonene (23%) and α-pinene (22%) as predominating components. Finally, the insect antijuvenile hormone precocene I was found to be present in all samples of the two varieties. Copyright

Composition of the essential oils from the leaves of Microglossa pyrifolia (Lam.) O. Kuntze and Helichrysum odoratissimum (L.) Less. growing in Cameroon

Four essential oil samples obtained by hydrodistillation from the leaves of Microglossa pyrifolia (Lam.) O. Kuntze and Helichrysum odoratissimum (L.) Less., respectively, were analysed by GC and GC–MS. The main constituents of the leaf oil of M. pyrifolia were found to be (E)-β-farnesene (78% and 73%) and β-caryophyllene (11% and 14%), whereas those of H. odoratissimum were α-Pinene (47% and 41%), β-caryophyllene (14% and 5%) and α-curcumene (4% and 20%). Copyright

The Essential Oil of Xylopia parviflora (A. Rich) Benth. from Cameroon

ABSTRACT Twenty-eight compounds have been identified in the essential oil of fruits of Xylopia parviflora. The major components were β-pinene (40.0%), α-pinene (14.0%), trans-ocimene (5.4%) and camphene (4.0%).