Chromatographic and spectroscopic studies on the constituents in male and female flowers of Hagenia abyssinica

Cytotoxicity of 91 Kenyan indigenous medicinal plants towards human CCRF-CEM leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Plants from Kenyan flora are traditionally used against many ailments, including cancer and related diseases. Cancer is characterized as a condition with complex signs and symptoms. Recently there are recommendations that ethnopharmacological usages such as immune and skin disorders, inflammatory, infectious, parasitic and viral diseases should be taken into account when selecting plants that treat cancer.

AIM

The present study was aimed at investigating the cytotoxicity of a plethora of 145 plant parts from 91 medicinal plants, most of which are used in the management of cancer and related diseases by different communities in Kenya, against CCRF-CEM leukemia cell line.

MATERIALS AND METHODS

Extracts from different plant parts (leaves, stems, stem bark, roots, root barks, aerial parts and whole herb) were obtained by cold percolation using different solvent systems, such as (1:1v/v) dichloromethane (CH2Cl2) and n-hexane (1), methanol (MeOH) and CH2Cl2 (2); neat MeOH (3), 5% H2O in MeOH (4) and with ethanol (EtOH, 5); their cytotoxicities were determined using the resazurin reduction assay against CCRF-CEM cells.

RESULTS

At a single concentration of 10μg/mL, 12 out of 145 extracts exhibited more than 50% cell inhibition. These include samples from the root bark of Erythrina sacleuxii (extracted with 50% n-hexane-CH2Cl2), the leaves of Albizia gummifera, and Strychnos usambarensis, the stem bark of Zanthoxylum gilletii, Bridelia micrantha, Croton sylvaticus, and Albizia schimperiana; the root bark of Erythrina burttii and E. sacleuxii (extracted with 50% CH2Cl2-MeOH), the stem bark of B. micrantha and Z. gilletii (extracted using 5% MeOH-H2O) and from the berries of Solanum aculeastrum (extracted with neat EtOH). The EtOH extract of the berries of S. aculeastrum and A. schimperiana stem bark extract displayed the highest cytotoxicity towards leukemia CCRF-CEM cells, with IC50 values of 1.36 and 2.97µg/mL, respectively. Other extracts having good activities included the extracts of the stem barks of Z. gilletii and B. micrantha and leaves of S. usambarensis with IC50 values of 9.04, 9.43 and 11.09µg/mL, respectively.

CONCLUSIONS

The results of this study provided information related to the possible use of some Kenyam medicinal plants, and mostly S. aculeastrum, A. schimperiana, C. sylvaticus, Z. gilletii, B. micrantha and S. usambarensis in the treatment of leukemia. The reported data helped to authenticate the claimed traditional use of these plants. However, most plants are used in combination as traditional herbal concoctions. Hence, the cytotoxicity of corresponding plant combinations should be tested in vitro to authenticate the traditional medical practitioners actual practices.

Characterization of Constituents and Anthelmintic Properties of Hagenia abyssinica

The dried female flowers of Hagenia abyssinica (Bruce) J. F. Gmel. (Rosaceae) are traditionally used as an anthelmintic remedy in Ethiopia and formerly were incorporated into the European Pharmacopoeia. One-, two- and tricyclic phloroglucinol derivatives (kosins) were suggested to be the active principles. However, polar constituents may also contribute to the activity. Therefore, we investigated for the first time the polar constituents. We isolated typical Rosaceae constituents such as quercetin 3-O-β-glucuronide, quercetin 3-O-β-glucoside and rutin. Polar kosin glycosides or derivatives could not be detected.The anthelmintic activity of fractions of different polarity were tested against the blood fluke Schistosoma mansoni, the liver flukes Clonorchis sinensis and Fasciola hepatica and the intestinal fluke Echinostoma caproni. The anthelmintic activity decreased with increasing polarity of the tested fractions. ESI-MS investigations indicated the predominant occurrence of kosins in the active fractions.Using the anthelmintic active extracts of Hagenia abyssinica we developed a simple, inexpensive bioassay against the non-parasitic nematode Caenorhabditis elegans, which can be used as an initial screening procedure for anthelmintic properties of crude extracts of plants or fungi. The anthelmintic activity of test extracts against the model organism was determined in a microtiter plate assay by enumeration of living and dead nematodes under a microscope.

Trypanocidal and antileukaemic effects of the essential oils of Hagenia abyssinica, Leonotis ocymifolia, Moringa stenopetala, and their main individual constituents

Essential oils from three Ethiopian medicinal plants; Hagenia abyssinica (Rosaceae), Leonotis ocymifolia (Lamiaceae), and Moringa stenopetala (Moringaceae) were investigated for their chemical composition, trypanocidal, and cytotoxic activities. Twenty components were identified from the essential oil of H. abyssinica female flowers, ledol (58.57%) being the principal volatile oil component. Sixty-eight components were identified from the essential oil of L. ocymifolia aerial part, caryophyllene oxide (12.06%) being the major component. The essential oil of M. stenopetala seeds was dominated by isothiocyanates; benzyl isothiocyanate (54.30%) and isobutyl isothiocyanate (16.37%) were the major components. The trypanocidal (Trypanosoma b. brucei) and antileukaemic (HL-60) effects of the three essential oils were studied. The oil of M. stenopetala seeds and its main compound, benzyl isothiocyanate showed the most potent trypanocidal activities with IC(50) values of 5.03 μg/ml and 1.20 μg/ml, respectively. The oils of H. abyssinica and L. ocymifolia exhibited trypanocidal activities with IC(50) values of 42.30 μg/ml and 15.41 μg/ml, respectively. Individual components (28 compounds) of the essential oils bearing different functional groups were also studied for their structure-activity relationships using trypanosomes and human leukaemia cells. Cinnamaldehyde (IC(50)=2.93 μg/ml) (a representative for aldehydes), nerolidol (IC(50)=15.78 μg/ml) (an alcohol), cedrene (IC(50)=4.07 μg/ml) (a hydrocarbon), benzyl isothiocyanate (IC(50)=1.20 μg/ml) (a representative for mustard oils), 1,8-cineole (IC(50)=83.15 μg/ml) (an ether), safrole (IC(50)=18.40 μg/ml) (aromatics with allyl and/or methoxy side chains), carvone (IC(50)=12.94μg/ml) (a ketone), styrene oxide (IC(50)=3.76 μg/ml) (an epoxide) and carvacrol (IC(50)=11.25 μg/ml) (a phenol) showed the most potent trypanocidal activities from their respective groups. Of all essential oil components tested, carvone (selectivity index (SI)=17.46) and styrene oxide (SI=19.92) showed good selective indices for the parasite with minimal toxicity on the human leukaemia cells. These compounds could therefore serve as lead structures for the development of trypanocidal agents with higher potency.

Determination of phloroglucinol in human plasma by gas chromatography-mass spectrometry

A specific and sensitive method has been developed for the determination of phloroglucinol in plasma; it involves an optimized procedure for blood sampling designed to minimize the in vitro oxidation of the molecule, and gas chromatography-mass spectrometry after silylation of the compound. The method allowed a reliable determination of phloroglucinol in plasma. The precision and accuracy of the assay, reported as coefficients of variation, were below 15%. Using a plasma sample of 0.25 ml, the limit of quantitation was 5 ng/ml with a precision of 17.4%, which is sensitive enough for pharmacokinetic studies. Stability studies under different conditions revealed that ascorbic acid limits the degradation of phloroglucinol in plasma during storage at freezer temperatures.

Evaluation of the anti-tumour action and acute toxicity of kosins from Hagenia abyssinica

The kosins are phloroglucinol derivatives isolated from female flowers of Hagenia abyssinica (Rosaceae) and were tested for possible cytotoxic activity in vitro and in vivo against a panel of three transplantable murine adenocarcinomas of the colon of varying growth characteristics and morphology (MAC system). Significant reductions in colony formation were observed in vitro in MAC 15A tumour following 1, 3, 6 and 24 h exposure to all kosins (alpha-kosin, kosotoxin and protokosin). The kosins (kosotoxin and protokosin) were also found to be cytotoxic against MAC tumour cells in vivo in some cases. Kosotoxin was subjected to preliminary toxicity studies in mice. It showed no observable toxicity up to 200 mg kg-1 orally and was found to be toxic at doses in excess of 50 mg kg-1 (i.p.). A single dose of 100 mg kg-1 (i.p.) was lethal for 100% of the animals.