Antimicrobial activities of some Ocimum species grown in Rwanda.

The essential oils of four Ocimum species grown in Rwanda, i.e. O. canum, O. gratissimum, O. trichodon and O. urticifolium (synonym O. suave) including some chemotypes, were screened for antimicrobial activities. Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Trichophyton mentagrophytes var. interdigitale were used as test organisms. Different techniques were applied in the screening, such as the biogram and agar overlay techniques and a dilution technique yielding maximum inhibitory dilution (MID) values. Also some growth curves were determined. Although the results obtained by the diffusion techniques were rather different for some of the oil samples, all samples were found to be antimicrobially active.

Screening of some essential oils for their activities on dermatophytes.

Fifty-three essential oils were tested against three frequently occurring dermatophytes (Epidermophyton floccosum, Trichophyton mentagrophytes var. interdigitale, T. rubrum) by means of an agar dilution technique. The oils were selected at random and not on the basis of a supposed activity. A number of oils showed interesting activities, expressed as maximum inhibitory dilution values, against the dermatophytes used. At the highest dilution tested (1:3,200, vol/vol), one out of six oils was active against T. mentagrophytes var. interdigitale, and one out of three to four oils was active against the other dermatophytes.

Antimicrobial activities of essential oils. A 1976-1986 literature review on possible applications.

The testing of essential oils for antimicrobial activities is reviewed with respect to various possible applications. Consideration is given to the screening for antimicrobially active oils or constituents, for disinfecting or antiseptic properties and for food conserving properties. The role of essential oils in biological interactions and their potential as therapeutic agents are also discussed.

Screening for antimicrobial activity of some essential oils by the agar overlay technique.

Fifty-three essential oils were tested against five micro-organisms (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans) using the agar overlay technique. The essential oils were randomly selected and not on the basis of a supposed activity. It was found that all oils showed an activity against at least one micro-organism, and that substantial activities against P. aeruginosa were scarce. Combined activities against C. albicans, the Gram-positive bacteria and E. coli, and an activity against C. albicans were most often observed. Secondly a combined activity against C. albicans, B. subtilis and S. aureus was found. The differences between the inhibition zones were too small for a differentiation of the antimicrobial activities of the essential oils. A correlation matrix shows the relationships of the micro-organisms as to the activity patterns of the essential oils. High correlations were found for all the micro-organisms, except for P. aeruginosa.

Research in the Division of Pharmacognosy.

About 50% of all drugs originate from plants and animals, especially from higher plants. The production of plant drugs often has to overcome several obstacles. The Division of Pharmacognosy of the Center for Bio-Pharmaceutical Sciences is involved in developing biotechnological production methods that may help to avoid such problems. In the research field of plant cell biotechnology there is a close co-operation with Delft. University of Technology. As an example some studies on tissue and suspension cultures of Cinchona species and on the biosynthesis of Cinchona alkaloids are described.

Anthraquinones as phytoalexins in cell and tissue cultures of Cinchona spec.

The addition of autoclaved mycelia of Aspergillus niger and the known phytopathogenic fungus Phytophtora cinnamomi to cultured cells of Cinchona ledgeriana Moens. caused a marked increase in the anthraquinone content of the plant cells. This finding in combination with the antimicrobial activity of the anthraquinones isolated from calli of Cinchona pubescens Vahl. led to the conclusion that anthraquinones are phytoalexins.

The essential oil of Ducrosia anethifolia (DC.) Boiss. Chemical composition and antimicrobial activity.

The essential oil from herb of Ducrosia anethifolia (DC.) Boiss., growing wild in Iran, was investigated by LSC, GLC and GC-MS. The oil consisted mainly of aliphatic compounds. alpha-Pinene, myrcene and limonene were main components of the hydrocarbons present in the oil, while n-decanal, n-dodecanal, n-decanol, trans-2-dodecenal, and cis-chrysanthenyl acetate were the major oxygen-containing constituents. The oil and the main oxygen-containing aliphatic components showed a remarkable antimicrobial activity against gram-positive bacteria, a yeast, and some dermatophytes.

The African Strychnos species and their alkaloids: a review.

A review of the phytochemistry of African Strychnos species and the biological activities of some species as well as of some individual alkaloids isolated from them is presented. Although pharmacological studies of 48 species showed that muscle-relaxant and/or convulsant properties were generally present, antimicrobial, cytotoxic and hypotensive properties among others have also been demonstrated by some of the species and/or alkaloids.

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.

Alkaloids from Tabernaemontana psorocarpa.

The isolation of the alkaloids from two different samples of stem bark of Tabernaemontana psorocarpa is described. Both samples contained 16-epi-isositsirikine as the major alkaloid but differed from each other in the number and quantity of the other alkaloids. The following minor alkaloids were identified: 12-methoxy-14,15-dehydro-vincamine, vallesiachotamine, isovallesiachotamine, tetrahydroalstonine, coronaridine and voacangine.

Cycleanine N-oxide, a new alkaloid from Synclisia scabrida.

A phytochemical investigation of the stems of Synclisia scabrida Miers (Menispermaceae) resulted in the isolation of a number of known bisbenzylisoquinoline alkaloids: cycleanine, norcycleanine, cocsuline and cocsoline. A new alkaloid, cycleanine N-oxide was also isolated.

Alkaloids from Chasmanthera dependens.

A phytochemical investigation of the stem of Chasmanthera dependens Hochst led to the isolation and identification of five quaternary alkaloids: jatrorrhizine, columbamine, pseudocolumbamine, magnoflorine and palmatine and nine tertiary non-phenolic alkaloids: tetrahydropalmatine, liriodenine, lysicamine, oxoglaucine, glaucine, anonaine, nornuciferine, norglaucine and O,O-dimethylcorytuberine.