K. Cimanga

Correlation between chemical composition and antibacterial activity of essential oils of some aromatic medicinal plants growing in the Democratic Republic of Congo.

The chemical composition of essential oils from 15 aromatic medicinal plant species growing in the Democratic Republic of Congo have been studied. More than 15 constituents in an amount higher than 0.1% were identified in each essential oil. 1,8-cineole, alpha and beta-pinene, p-cymene, myrcene, gamma-terpinene, alpha-terpineol and limonene were prevalent constituents in almost more than 10 selected plant species. Results from the antibacterial testing by the diffusion method indicate that all essential oils (5 microl per disc) inhibited the growth of selected bacteria at different extents. The most active antibacterial essential oils were those of the leaves of Eucalyptus camadulensis and Eucalyptus terticornis (12-30 mm zone diameter of inhibition). They showed particularly a most potent inhibition of Pseudomonas aeruginosa growth (15-16 mm), followed by Eucalyptus robusta (12 mm). Essential oils from the leaves of Eucalyptus alba, Eucalyptus citriodora, Eucalyptus deglupta, Eucalyptus globulus, Eucalyptus saligna, Eucalyptus robusta, Aframomum stipulatum, Cymbopogon citratus, Ocimum americanum and that of the seeds of Monodora myristica showed also a good antibacterial activity (10-18 mm). Eucalyptus propinqua, Eucalyptus urophylla and Ocimum gratissimum essential oils were the less active samples against the selected bacteria. No correlation between the amount of major constituents such as 1,8-cineol, alpha-pinene, p-cymene, cryptone or thymol and the antibacterial activity was observed.

Antiamoebic and phytochemical screening of some Congolese medicinal plants.

Results from the in vitro antiamoebic activity of some Congolese plant extracts used as antidiarrhoeic in traditional medicine indicated that of 45 plant extracts tested, 35 (77.78%) exhibited an antiamoebic activity and 10 (22.22%) were inactive. The highest activity (MIC < 100 microg/ml) was obtained with extracts from root bark of Paropsia brazzeana, Cryptolepis sanguinolenta, Alchornea cordifolia, Hensia pulchella, Maprounea africana, Rauwolfia obscura and Voacanga africana, leaves and stem bark of Psidium guajava, stem bark of Dialum englerianum, Harungana madagascariensis and Mangifera indica, mature seeds of Carica papaya, and leaves of Morinda morindoides and Tithonia diversifolia. Metronidazole used as reference product showed a more pronounced activity than that of all plant extracts tested.

Antimalarial activity of 20 crude extracts from nine African medicinal plants used in Kinshasa, Congo.

Twenty extracts including ten EtOH and ten CH2Cl2 from different parts of nine African medicinal plants used in Congolese traditional medicine for the treatment of malaria, were submitted to a pharmacological test in order to evaluate their effect on P. falciparum growth in vitro. Of these plant species, 14 (70%) extracts including EtOH and CH2Cl2 from Cassia occidentalis leaves, Cryptolepis sanguinolenta root bark, Euphorbia hirta whole plant, Garcinia kola stem bark and seeds, Morinda lucida leaves and Phyllanthus niruri whole plant produced more than 60% inhibition of the parasite growth in vitro at a test concentration of 6 microg/ml. Extracts from E. hirta, C. sanguinolenta and M. morindoides showed a significant chemosuppression of parasitaemia in mice infected with P. berghei berghei at orally given doses of 100-400 mg/kg per day.

New alkaloids from Cryptolepis sanguinolenta

Neocryptolepine and biscryptolepine, two new alkaloids, were isolated from the root bark extract of the African medicinal plant, Cryptolepis sanguinolenta (Lindl.) Schlechter (Periplocaceae), and their structures elucidated on the basis of spectral evidence. The 1H and 13C NMR assignments of cryptoquindoline, a known artefact, were revised.

Antiamoebic and spasmolytic activities of extracts from some antidiarrhoeal traditional preparations used in Kinshasa, Congo.

Three major extracts from some traditional preparations, based on medicinal plants, used as antidiarrhoeal agents were investigated for their putative antiamoebic and spasmolytic activities in vitro. Results indicated that both biological activities are concentrated in the polyphenolic fraction, and not in the saponin or alkaloid containing fractions. The most active polyphenolic extracts were those from Euphorbia hirta whole plant, leaves of Alchornea cordifolia, Crossopteryx febrifuga, Nauclea latifolia, Psidium guajava, Tithonia diversifolia, stem bark of Harungana madagascariensis, Mangifera indica, Maprounea africana and Psidium guajava, inhibiting Entamoeba histolytica growth with MAC < 10 micrograms/ml. The same extracts, at a concentration of 80 micrograms/ml in an organ bath, also exhibited more than 70% inhibition of acetylcholine and/or KCl solution-induced contractions on isolated guinea-pig ileum.

In-vivo antimalarial activity of Cassia occidentalis, Morinda morindoides and Phyllanthus niruri.

The ethanolic, dichloromethane and lyophilized aqueous extracts of Cassia occidentalis root bark, Morinda morindoides leaves and whole plants of Phyllanthus niruri were evaluated for their antimalarial activity in vivo, in 4-day, suppressive assays against Plasmodium berghei ANKA in mice. No toxic effect or mortality was observed in mice treated, orally, with any of the extracts as a single dose, of 500 mg/kg body weight, or as the same dose given twice weekly for 4 weeks (to give a total dose of 4 g/kg). No significant lesions were observed, by eye or during histopathological examinations, in the hearts, lungs, spleens, kidneys, livers, large intestines or brains of any mouse. At doses of 200 mg/kg, all the ethanolic and dichloromethane extracts produced significant chemosuppressions of parasitaemia (of > 60% for C. occidentalis root bark and Ph. niruri whole plant, and of 30% for M. morindoides leaves) when administered orally. The most active ethanolic extract, that of Ph. niruri, reduced parasitaemia by 73%. The dichloromethane extracts of M. morindoides and Ph. niruri produced similar reductions (74% and 72% chemosuppression, respectively), whereas that of C. occidentalis was slightly less active (60% chemosuppression). Each lyophilized aqueous extract was less active than the corresponding ethanolic extract.

Biological screening of traditional preparations from some medicinal plants used as antidiarrhoeal in Kinshasa, Congo

Forty six aqueous extracts from 38 medicinal plant species belonging to different families were selected on the basis of their traditional medicinal use as antidiarrhoeic agents. They were submitted in a broad biological screening including antibacterial, antiamoebic and antispasmodic activities. The results of the testing have indicated that 37 extracts (80.43%), 33 (71.74%) and 32 (69.54%) exhibited some level of antibacterial, antiamoebic and antispasmodic activity respectively. Only 8 plant extracts (17.39%) would act as antidiarrhoeic agents by a triple pronounced antibacterial, antiamoebic and antispasmodic action. They include aqueous extracts from Euphorbia hirta whole plant, leaves of Psidium guajava and Tithonia diversifolia, root bark of Alchornea cordifolia, Heinsia pulchella, Paropsia brazzeana, Rauwolfia obscura and Voacanga africana.

Radical scavenging and xanthine oxidase inhibitory activity of phenolic compounds from Bridelia ferruginea stem bark

Bridelia ferruginea Benth. (Euphorbiaceae) is a subtropical medicinal plant widely used in traditional African medicine against various diseases, including rheumatic pains. Seven of its constituents (3‐O‐methylquercetin (1), 3,7,3′,4′‐tetra‐O‐methylquercetin (rutisin, 2), myricetin (3), 3′,4′,5′‐tri‐O‐methylmyricetin (ferrugin, 4), 3,3′,4′,5′‐tetra‐O‐methylmyricetin (5), quercetin 3‐O‐glucoside (6), and a biflavanol gallocatechin‐[4′‐O‐7]‐epigallocatechin (7)) have been evaluated in‐vitro in the xanthine‐xanthine oxidase enzymatic system for inhibition of xanthine oxidase and radical scavenging activity. Results indicated that compounds 1, 3, 4 and 6 exhibited, at different levels, xanthine oxidase inhibiting and superoxide scavenging activity at micromolar concentrations, whereas compound 7 showed scavenging activity only. Compounds 2 and 5 were inactive in both cases. Study of the structure‐activity relationship demonstrated that for flavonoids the xanthine oxidase inhibitory activity was reduced by methylation of the hydroxyl functionality at C‐3 and in rings A and B. These results may partly explain and support the use of B. ferruginea stem bark for the treatment of rheumatic pains in traditional medicine.

Antibacterial and antifungal activities of neocryptolepine, biscryptolepine and cryptoquindoline, alkaloids isolated from Cryptolepis sanguinolenta

From the 80% EtOH extract of Cryptolepis sanguinolenta (Lindl.) Schlechter (Periplocaeae) root bark, a cryptolepine isomer named neocryptolepine, and two dimeric alkaloids named biscryptolepine and cryptoquindoline were isolated. These compounds were tested for their putative antibacterial and antifungal activities. Results have indicated that neocryptolepine showed an antibacterial activity against Gram-positive bacteria (MIC < 100 μg/ml), but was less acive against Gram-negative bacteria. It also inhibited the growth of the yeast C. albicans. Biscryptolepine exhibited only an activity against some Gram-positive bacteria (MIC = 62.5 or 31 μg/ml) while cryptoquindoline did not shown an activity against all selected microorganisms. The antibacterial activity of neocryptolepine and biscryptolepine is bacteriostatic rather than bactericidal. No antifungal activity could be observed for all alkaloids in our test system at the highest test concentration of 100 μg/ml.

Chemical Composition and Antifungal Activity of Essential Oils of Some Aromatic Medicinal Plants Growing in the Democratic Republic of Congo

Abstract The chemical composition and the antifungal activity of essential oils from 15 aromatic medicinal plant species growing in the Democratic Republic of Congo have been studied. More than 15 constituents in an amount ≥ 0.1% were identified in each oil. 1,8-Cineole, α- and β-pinene, P-cymene, α-terpineol, camphene and limonene were prevalent constituents. The antifungal activity of these oils (5 μL per disc) was evaluated by the diffusion method. Results indicate that all oils from fresh plant materials exhibited an antifungal activity at different levels against Candida albicans, Candida tropicalis, Aspergillus niger, Trichophyton mentagrophytes and Microsporum canis. A high antifungal activity was found in the leaf oil of E. tereticornis (15–22 mm) followed by the leaf oils of Eucalyptus alba (14–17 mm), E. camaldulensis, E. citriodora, E. globulus, Cymbopogon citratus and Monodora myristica seed oil (11–17 mm) against selected yeasts, fungus and dermatophytes. The leaf oils of E. deglupta, E. robusta, Ocimum gratissimum and Aframomum stipulatum also showed a good activity against selected microorganisms (10–12 mm). The less active oils were those from E. saligna, E. propinqua and O. americanum leaves. No correlation between the amount of some major constituents and the antifungal activity was observed.