Khat (Catha edulis)-induced apoptosis is inhibited by antagonists of caspase-1 and -8 in human leukaemia cells

Khat, a Cultural Chewing Drug: A Toxicokinetic and Toxicodynamic Summary

Khat (Catha edulis) is a recreational, chewed herbal drug that has been used as a psychostimulant for centuries in East Africa and the Arabian Peninsula, namely in Somalia, Ethiopia, and Yemen. However, the growing worldwide availability of khat has produced widespread concern. The plant comprises a large number of active substances, among which cathinone, cathine, and norephedrine are the main constituents, which can be included in the group of sympathomimetics of natural origin. In fact, these compounds are amphetamine analogues, and, as such, they have amphetamine-like nervous system stimulant effects. Chewing the leaves gives people a sensation of well-being and increases energy, alertness, and self-confidence. The chronic use of khat is, however, associated with severe cardiac, neurological, psychological, and gastrointestinal complications. The psychological dependence and withdrawal symptoms of khat are the reasons for its prolonged use. The aim of this paper is to review current knowledge on the khat plant with toxicokinetic and toxicodynamic perspectives. Namely, this review paper addresses in vitro, in vivo, and human studies. The models used, as well as the concentrations and doses with the respective biological effects, are discussed. Additionally, the main drug interactions involved with khat are described.

Khat (Catha Edulis Forsk) induced apoptosis and cytotoxicity in cultured cells: A scoping review

Background

Khat (Catha edulis Forsk) leaves are chewed by people in certain regions of East Africa and the Middle East for their stimulating amphetamine-like effects. The purpose of this scoping review is to systematically map the current in vitro publications that investigated the toxicological potential effects of khat on cultured human or animal cells in terms of cellular viability and activity.

Methods

A comprehensive electronic database search was undertaken up to December 2020 without starting date or language restrictions in accordance with the PRISMA extension for scoping review guideline and methodological quality evaluation based on the guidelines for reporting pre-clinical in vitro studies on dental materials. All in vitro studies that investigated the effect of khat plant extract (Catha Edulis) on the cultured human or animal cells were included.

Results

The initial search yielded 599 articles and 16 articles were finally selected to be included. The treatment of cells with khat produced different degrees of cellular changes, including decreased cellular survival, induction of apoptosis, increased ROS production, alteration of cell phenotype, and of arrest cell cycle. In this contest, khat-exposed cells expressed higher levels of pro-apoptotic protein Bax and lower levels of anti-apoptotic Bcl-2, up-regulated p38, p53, p16, and p21 proteins, as well as premature expression of differentiation markers.

Conclusion

Based on the current scoping review, khat induced apoptosis and cytotoxicity in cultured human cells, including oral cells.

Progress and Research Trends on Catha edulis (Vahl) Endl. (Catha edulis): A Review and Bibliometric Analysis

Catha edulis (Vahl) Endl., known as Catha edulis or Khat is a traditional and regional plant for chewing, smoking and drinking, that has posed a worldwide public health problem due to its recent emerging abused consumption. In the face of the massive use of Catha edulis, we reviewed related publications to analyze the progress and research trends through bibliometric methods. After screening, a total of 514 scientific publications published from 1997 to 2020 were included by systematic retrieval from the Web of Science (WoS) database. According to further scientometric analysis, the annual number of publications output kept rising in most of the years. Ethiopia and the United States of America (USA) have been devoting significant contributions to the field. Though the research emphasis had been the chemical composition and pharmacological and toxicological effects for several years, the hot spots were transferred; the mechanism investigations of Catha edulis have been the focus in recent years, which might be continued in the future. Furthermore, co-operations of multi-disciplinary researchers are needed to minimize abuse harms and maximize the medicinal benefits of Catha edulis to human beings.

Qualitative ultrastructural analysis of the submandibular salivary glands after administration of khat: in vivo study

Objective

Khat (Catha edulis Forssk) plant has been widely chewed for its psychostimulatory effects in the African and Arabian Peninsula, particularly in Yemen. Considering the khat leaves are gradually chewed without swallowing, while its active constituents are extracted into saliva, studying the effect of khat on salivary glands is necessary. This work is an extension of the previously published work that studied the effect of khat extract on the rats' submandibular salivary glands in terms of histological and immunohistochemical evaluations. The current research note aimed to better understand this effect on the ultrastructure of submandibular salivary gland cells by using transmission electron microscope.

Results

Oral administration of khat extract produced degenerative changes in the secretory and ductal cells of rats' submandibular salivary glands. These changes involved irregular boundaries of variable sized-nuclei, dilated RER, cytoplasmic vacuoles as well as swollen and degenerated mitochondria.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05595-8.

Unraveling the Catha edulis Extract Effects on the Cellular and Molecular Signaling in SKOV3 Cells

Khat (Catha edulis (Vahl) Endl.) is an evergreen flowering shrub used as a stimulant in many regions worldwide including East Africa, the Arabian Peninsula, Europe, and the United States. Chewing leaves of khat induces excitement and euphoria, which are primarily attributed to two major constituents, cathinone and cathine. Khat also contains other important constituents such as cathedulins. A considerable number of studies reported side effects induced by the khat extracts to both embryos and adults. These include teratogenicity and developmental retardation, oral cancer and ulcers, high blood pressure, and myocardial infarction. So far, little attention has been paid to the effects of khat extracts on the molecular signaling interactions. We aimed in this study to investigate this through evaluating the effects of khat extracts on SKOV3, a human ovarian adenocarcinoma cell line. We show, by in vitro assays, that khat induces several cellular defects including reduced cell size, cell membrane damage, and apoptosis. At high khat extract concentrations, the cell metabolic activity, cell cycle, and cellular proliferation were affected. RT-qPCR analysis showed an increase in the gene expression of the apoptotic marker BAX, the tumor suppressor p53, and the inflammatory cytokine IL-6. Protein expression analysis by immunostaining showed downregulation of β-catenin, E-cadherin, and Ki-67 and upregulation of FZD8 and SPRY2, suggesting that Wnt and FGF signaling were implicated. SwissTargetPrediction in silico analysis showed that khat constituents cathine, cathinone, catheduline K2, and catheduline E5 bind to family A G-protein-coupled receptor, cause many neurological diseases and disorders such as Alzheimer's, schizophrenia, depression, and anxiety, and induce many ovarian cancer-related diseases. The analysis also showed that important signaling pathways such as CREB, Wnt, FGF, IL-6, and ERK/MAPK, and that of the endometrial cancer, and cell cycle were implicated. Upstream regulators of cathine and cathinone were found to potentially target several molecules including interleukin-8, MMP2, PLAU, and micro-RNAs. In conclusion, khat induces significant cellular and molecular changes that could potentially cause a wide range of serious diseases and syndromes. Such an impact could have a heavy burden on the health care system in the countries where khat is consumed.

A Comparison of p53 Isoform Profiles and Apoptosis Induced by Camptothecin or a Herbal Khat Extract (Catha Edulis (Vahl) Forssk. ex Endl.) in Leukemic Cell Lines: Exploring Cellular Responses in Therapy Development

Simple Summary

This study aimed at exploring the modulations of p53 in cell toxicity induced by an extract of the herb khat, a natural stimulant used by millions of people. We previously reported that khat-extract induced cell death by affecting mitochondrial function and the receptor- and mitochondria-mediated cell death pathways, in leukemic cell lines and cells of the oral cavity, in vitro. We included the cancer therapeutic camptothecin, which induces apoptosis in various cancer cell lines. By studying modulations of p53 full-length protein and p53 β/γ isoforms following exposure to khat-extract and camptothecin, we wished to elucidate differences and similarities resulting from the treatments using MOLM-13 and MV-4-11 leukemic cell lines. Our results demonstrate that molecular effects of the cytotoxic treatments resulted in different p53 isoforms patterns and post-translational modifications. We suggest that analysis of p53 modulations could be useful in the search for new chemical probes and experimental cancer therapeutics.

Abstract

Khat (Catha edulis (Vahl) Forssk. ex Endl.) is habitually used as a natural stimulant by millions of people, but is associated with adverse effects on gastrointestinal, cardiovascular and central neural systems. At the cellular level khat toxicity involves p53 induction and cell cycle arrest, decreased mitochondrial function and activation of receptor- and mitochondria-mediated cell death pathways. In this study we have examined an extract of khat for induction of p53 post-translational modifications (PTMs) and the functional role of p53 in khat-mediated cell death. Khat was shown to induce phosphorylation and acetylation of p53 in both the khat-sensitive MOLM-13 and the khat-resistant MV-4-11 cell line, but accumulation of the full-length p53 isoform was only observed in the khat sensitive cell line. Small molecule inhibitors of p38 MAP kinase sensitized MV-4-11 cells for khat-treatment without concomitant stabilization of p53. Experiments using a p53 knock-down cell line and murine p53 knock-out bone marrow cells indicated that p53 was redundant in khat-mediated cell death in vitro. We suggest that analysis of isoform patterns and p53 PTMs are useful for elucidation of biological effects of complex plant extracts, and that p53 protein analysis is particularly useful in the search for new chemical probes and experimental cancer therapeutics.

Exploring the Molecular Mechanisms of 17β-HSD5-induced Carcinogenicity of Catha edulis via Molecular Modeling Approach

BACKGROUND

The tradition of khat chewing has been deep-rooted in the African and Arabian Peninsula for centuries. Due to its amphetamine-like psycho-stimulant or euphoric effect, khat has been used by millions in Somalia, Ethiopia, Saudi Arabia and Yemen. The long-term use of khat can induce many major health outcomes, which may be serious and irreversible.

OBJECTIVE

Prolonged use of khat constituents has been associated with different types of cancers such as prostatic, breast and ovarian cancer. However, it has been very difficult to identify the molecular targets involved in khat carcinogenesis that interact with the Khat constituents by in vitro/in vivo experimental tools.

METHODS

In silico tools were used to predict potential targets involved in the carcinogenesis of khat. Pass on-line prediction server was used for the prediction of a potential molecular target for khat constituents. Molecular Dynamics simulation and MM-GBSA calculation of the predicted target were carried out.

RESULTS

Molecular Dynamics simulation and MM-GBSA calculation revealed that among khat constituents, β-sitosterol showed a high binding affinity towards 17β-HSD5. On the other hand, this study highlights for the first time some new interactions, which were observed in the case of cathine, cathinone and nerol during the simulation.

CONCLUSION

In silico molecular dynamic simulation tools were used for the first time to investigate the molecular mechanism of widely used leaves of psychoactive khat (Catha edulis) constituent. The present study provides deep insight to understand the effect of khat constituents involved in the impairment of the reproductive system and its binding to 17β-HSD5. ADMET profiling also suggested that few khat constituents do not fulfill the requirements of the Lipinski rule of five i.e. poor absorption and blood-brain barrier impermeability.

Evaluation of Khat (Catha edulis) Use as a Risk Factor of Cancer: A Systematic Review

Background:

Conducting systematic review to evaluate plant use as a risk factor to cancer could be challenging. A systematic and well-balanced method should be applied to accommodate in vivo and in vitro studies to make a final decision. In this article, khat, a recreational plant used in some Arabic and African regions, was employed as an example to systematically determine its relationships to the premalignant and cancerous conditions.

Methods:

Systematic database search was performed to recruit original human, animal or in vitro studies on khat and cancer. Sixteen studies fulfilled the inclusion criteria and subjected to assessment using Risk of Bias (RoB). Office of Health and Translation (OHAT) approach was used to rate the confidence level in the body of evidence. The evidence was integrated to establish the relationships between khat, premalignant conditions and cancer.

Results:

Seven out of eight studies showed that khat causes premalignant oral lesions with moderate evidence level. Four studies showed that khat causes cancer with low evidence level and another three studies showed that khat has anti-cancer effect with moderate to high evidence level. Only one study suggested that khat is unrelated to cancer.

Conclusion:

RoB and OHAT approach are reliable systematic tools to evaluate plant risk to cancer and provide objective and uniform summary regardless of the study type. In conclusion, our pooled analysis did not find a direct relationship between khat and cancer but anti-cancer effect would require to be proofed on human studies.

Phytochemical Screening and Cytotoxic Properties of Ethanolic Extract of Young and Mature Khat Leaves

The khat plant has been culturally used in many parts of Africa and the Arabian Peninsula for many years to induce psycho-stimulating effect. Because of the global wide-spreading nature, khat chewing is being considered as a universally growing problem. Catha abbottii, Catha edulis, and Catha transvaalensis are the three species of khat commonly chewed in Saudi Arabia and nearby regions. Khat users usually prefer to chew young leaves over mature ones due to the diverse effects produced by both. Though many of the constituents of khat leaves have been identified, the complete phytochemical profile of young and mature leaves was not performed or compared; also, no evidence is available to affirm the cytotoxicity of young or mature leaves. Therefore, this study aimed to investigate the phytochemical basis of the differential response of the young and mature leaves and to assess the cytotoxicity of young and mature khat leaves. Ethanolic extracts of young and mature leaves of three khat cultivars were subjected to GC-MS. Hierarchical cluster analysis revealed the existence of two major clusters. The extracts of young leaves were found to contain the maximum content of cathinone; however, methoxyamphetamine was found in only one extract of young leaves. Cytotoxicity investigations were also conducted on both types of leaves using three cancer cell lines, human breast adenocarcinoma, human ovary adenocarcinoma, and human colon adenocarcinoma and also normal human fetal lung fibroblast cell line was used. All extracts showed comparable cytotoxicity, IC50 ranging from 22–59 μg/mL on the cancer cells; however, we observed more cytotoxicity against normal cells (IC50: 6–41 μg/mL). The predominant cytotoxicity on normal cells may pose many health hazards to khat consumers.

Khat promotes human breast cancer MDA-MB-231 cell apoptosis via mitochondria and MAPK-associated pathways

Khat (Catha edulis Forsk) is a flowering evergreen plant in Eastern Africa and Southwestern Arabia. Consumption of Khat has been associated with the development of oral cancer, but its mechanism of action on the molecular level remains unclear. The present study demonstrated the cytotoxic effect of khat extracts on the human breast cancer cell line MDA-MB-231. Trypan blue exclusion assays, flow cytometry, fluorescent and electron microscopy, as well as western blotting were used to analyze the effects of Khat on the cell viability of breast cancer cells, expression of apoptotic-associated proteins and the levels of reactive oxygen species (ROS). The results of the present study demonstrated that treatment with 400 µg/ml khat was able to induce cell death in breast cancers, with an increase in the protein expression of apoptosis regulator Bax and a decrease in the expression of B-cell lymphoma 2, along with a decrease in ROS levels in a time-dependent manner. Furthermore, the expression of activated c-Jun N-terminal and extracellular regulated protein kinases was increased in khat-treated cells compared with untreated cells. Mitochondria participated in cell apoptosis through the release of apoptogenic proteins to the cytosol and the generation of excess reactive oxygen species. The results of the present study suggest that khat induces MDA-MB-231 cell apoptosis via MAPK activation and mitochondrial-mediated death.

Pharmacological and Toxicological Effects of Catha edulis F. (Khat)

Khat chewing is deeply rooted in the culture and tradition of communities in khat belt countries, and its consumption is spread to other countries through the suitcase trade. The aim of this article is to review current knowledge on the chemistry, social, pharmacology and toxicology of khat and its use. Khat produces effect invariably in every system, which is harmful or beneficial in some instances. Harmful effects are observed in heavy users, although firm evidence is lacking. Chewing khat acutely elicits states of euphoria, which is followed by low mood. Khat contains alkaloids with psychostimulant properties, but the effect cannot be totally explained by these alkaloids. It is also not clear whether the effect produced in some organs like liver could be attributed to khat or pesticides sprayed during farming. Although the evidence indicates that khat has adverse effects in most organs, our understanding of the complex interaction between use and effect is incomplete, and causal relationships have not yet been described. Moreover, khat has positioned itself well in the social, economic and political arena. Thus, a multidisciplinary research is required to understand the different dimensions and come up with ways that maximize the benefit while minimizing the risk. Copyright © 2017 John Wiley & Sons, Ltd.

Catha edulis Extract Induces H9c2 Cell Apoptosis by Increasing Reactive Oxygen Species Generation and Activation of Mitochondrial Proteins

Background:

Catha edulis (Khat) is an evergreen shrub or small tree, traditionally used by various peoples of the Arabian Peninsula and Africa as an integral component of the socioeconomic traditions. It is believed that the psychostimulant nature and toxic nature of khat is primarily due to the presence of cathinone and cathine respectively. Studies have shown that khat chewing is closely associated with cardiac complications, especially myocardial infarction. Hence in this study, we exposed cathine-rich khat extract in a cardiomyoblast H9c2 (2-1) cell line to check the cell death mechanism.

Materials and Methods:

Extraction of Catha edulis leaves was done and the presence of cathine was confirmed with LC-MS-MS. The anti-proliferative activity was assayed using MTT and apoptosis detection by acridine orange/propidium iodide assay. The expression of Bcl-2 and Bax protein and caspase-3/7 expression were analyzed. The level of reactive oxygen species generation was also evaluated.

Results:

The khat extract showed an IC50 value of 86.5 μg/ml at 48 hours treatment. We have observed significant early apoptosis events by intervened acridine orange within the fragmented DNA with bright green fluorescence upon treatment. The Bcl-2 expression in the treatment with IC50 concentration of khat extract for 24, 48 and 72 hours of incubation significantly decreased with increase in bax level. The increased activation of caspase-3/7 was significantly observed upon treatment together with significant increase of ROS was detected at 24 and 48 hours treatment.

Conclusion:

Collectively, our results provide insight into the mechanisms by which Catha edulis leaves mediate cell death in cardiomyocytes.

SUMMARY

Catha edulis (Khat) is an evergreen psychotropic shrub or small tree

Extraction of khat leaves was done and the presence of cathine was confirmed with liquid chromatography-mass spectrometry-mass spectrometry

The khat extract showed an IC⁵⁰ value of 86.5 μg/ml at 48 h treatment in H9c2 (2–1) cell line

The observed cell death was associated with increased expression of Bcl2 and caspase-3

Significant increase of reactive oxygen species was also detected in the cell with treatment.

Abbreviations used: CNS: central nervous system; AMI: acute myocardial infarction; TLC: thin layer chromatography; ESI: electrospray ionization; FBS: fetal bovine serum; DMSO: dimethylsulfoxide; AO; acridine orange; PI; propidium iodide; HRP: horseradish peroxidase; HBSS: hank's balanced salt solution; DCFH-DA: 2’,7’-dichlorofluorescin diacetate; NAC, 10 mM: NAC: N-acetyl cysteine; ROS: reactive oxygen species.

Catha edulis (khat) Induces Apoptosis in Madin-Darby Bovine Kidney Cell Line

Background:

Khat (Catha edulis) is a controversial plant having a euphoretic effect, at the same time part of culture in many countries such as Africa and Arabian Peninsula. The presence of amphetamine-like substance, cathinone and cathine make this plant banned in many countries. Many neurological and other system related studies have been carried out in this plant, but the lack of toxicity studies are there especially the mechanism.

Objective:

In this study, Madin-Darby Bovine Kidney cell line was used as an in vitro model to study the cell death mechanism. Crude extract of fresh Khat plant leaves were prepared and exposed to cells.

Materials and Methods:

Trypan blue assay, phase-contrast microscopy, fluorescent microscopy, clonogenic assay, annexin-V assay, and hematoxylin and eosin (H and E) staining were employed to check the objectives.

Results:

Reductions in cellular viability were observed at concentrations above 1.25 mg/ml while using Trypan blue assay. The results of the clonogenic assay had shown that the untreated control with the highest number of colonies (100% survival) and the 0.1562 concentration could not prevent the colony formation significantly. The high concentrations reduced the colony formation at concentration dependent manner 27.4% and 24.9%, for 0.625 mg/ml and 1.25 mg/ml concentrations, respectively. The acridine orange/ethidium bromide experiment had observed the cells were intact with round nucleus while the apoptosis features such as blebbing and nuclear chromatin condensation were clearly observed in treatment. The shrinkage of cells was clearly observed in H and E staining.

Conclusion:

In addition, annexin-V binding confirmed the presence of apoptosis significantly on Khat treatment.

SUMMARY

Khat (Catha edulis) is a controversial plant having euphoretic effect

Reductions in cellular viability were observed at concentrations above 1.25 mg/ml while using Trypan blue assay

The high concentrations of khat extract had reduced the colony formation at concentration dependent manner

The acridine orange/ethidium bromide experiment had observed the apoptosis features such as blebbing and nuclear chromatin in treatment

Annexin-V binding confirmed the presence of apoptosis significantly on Khat treatment.

Abbreviation used: PS: Phosphatidylserine (PS); MDBK: Madin-Darby Bovine Kidney; DMEM: Dulbecco's modified Eagle's medium; PI: propidium iodide; EB: ethidium bromide; PBS: Phosphate Buffer saline; FITC: fluorescein isothiocyante; TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling.

Qat Chewing and Periodontal Pathogens in Health and Disease: Further Evidence for a Prebiotic-Like Effect

AIM

Qat chewing has been reported to induce subgingival microbial shifts suggestive of prebiotic-like properties. The objective here was to assess the effect of qat chewing on a panel of classical and new putative periopathogens in health and periodontitis.

MATERIALS AND METHODS

40 qat chewers and 40 nonchewers, equally stratified by periodontal health status, were recruited. Taqman, real-time PCR was used to quantify total bacteria, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Parvimonas micra, Filifactor alocis, Synergistetes, and TM7s in pooled subgingival biofilm samples. Differences in microbial parameters between the study groups were analysed using ordinal regression.

RESULTS

In health, the qat chewers harboured significantly lower relative counts of P. gingivalis, T. forsythia, Synergistetes, and TM7s after adjustment for multiple comparisons (P ≤ 0.007). At nominal significance level, they also carried lower counts of TM7s and P. micra (P ≤ 0.05). In periodontitis, the chewers had lower counts of all taxa; however, only T. denticola withstood correction for multiple comparisons (P ≤ 0.0063).

CONCLUSIONS

Qat chewing is associated with lower proportions of periopathogens, particularly in subjects with healthy periodontium, which supports previous reports of its prebiotic-like properties. This potentially beneficial biological effect can be exploited by attempting to isolate the active fraction.

Qat Chewing and Risk of Potentially Malignant and Malignant Oral Disorders: A Systematic Review

BACKGROUND

Qat (also known as Khat, Kat and Miraa) is a green-leaved plant (Catha edulis). It is a shrub indigenous to Yemen and certain parts of eastern Africa. Chewing the leaves, which have sympathomimetic and euphoric effects, has been documented in many countries and increased with worldwide migration. The effect of long-term chewing Qat on the oral cavity is unknown.

OBJECTIVE

A systematic review was performed to identify any associations between Qat chewing and the occurrence of potentially malignant and malignant oral disorders.

METHODS

Medline and the Web of Science were searched for articles published before May 2014 without limits with regard to publication date and language.

RESULTS

From a total of 890 papers identified, 17 English papers reported potentially malignant or malignant oral disorders and Qat chewing. One additional paper in Arabic language was identified from reviewing the list of references of eligible papers. It was found that exposure to Qat may be associated with potentially malignant and malignant oral disorders, but methodological issues, such as inadequate study design, sample size, selection of study subjects, clinical evaluations of outcome and limited adjustment for confounders, limit the strength of the evidence base in this area.

CONCLUSION

The association between Qat chewing and potentially malignant and malignant oral disorders remains debatable and requires further investigations.

Effect of chronic khat (Catha edulis, Forsk) use on outcome of Plasmodium berghei ANKA infection in Swiss albino mice

Background

The objective of this study was to explore effects of khat (Catha edulis) on outcome of rodent malaria infection and its anti-plasmodial activities on Plasmodium berghei ANKA (PbA).

Methods

Female Swiss albino mice were orally treated with crude khat (Catha edulis) extracts (100, 200 and 300 mg/kg) on a daily basis for 4 weeks prior to PbA infection. Physical, clinical, hematological, biochemical and histo-pathological features of the mice were assessed. In addition, in vivo anti-plasmodial activities of khat were evaluated.

Results

The finding of this study showed that khat use was strongly associated with increment of levels of liver and kidney biomarkers, leucopenia, severe anemia, rise in level of inflammation biomarkers: C-reactive protein (CRP), uric acid (UA), increased monocyte-lymphocyte count ratio (MLCR), manifestation of cerebral malaria symptoms such as ataxia, paralysis and deviation of the head but with no pulmonary edema. Significantly lower level of parasitemia (P < 0.05), rectal temperature, but, high level of hemoglobin were observed at the early stage of the PbA infection in khat treated mice than the control. With extension of the treatment period, however, drastic increments were observed in parasite load and rectal temperature although there was reduction in hemoglobin (Hb) level. Moreover, khat showed poor anti-plasmodial activity with <10% parasite suppression activity and lack protection against major malaria symptoms. The significant reduction (P < 0.01) of hematological parameters during PbA infection strengthen the notion that hematological parameters could be good predictors of severe malaria complications in human.

Conclusions

In mice model treated with khat prior to infection with the rodent malaria parasite, khat was found to worsen manifestation of most malaria complications. Furthermore, the same plant showed poor in vivo anti-plasmodial activity and protection against major malaria symptoms.

Effect of Khat on apoptosis and related gene Smac/DIABLO expression in the cerebral cortex of rats following transient focal ischemia

BACKGROUND

The leaves of the Khat shrub contain the major alkaloid compounds (cathinone) and cathine. These compounds can induce apoptosis and exacerbate the acute cerebral infarction, but the underlying mechanism is poorly understood. The present study aimed to investigate the effects of Khat treatment on the expression and cellular localization of Smac/Diablo (second mitochondrial activator of caspase) in the cortex of ischemic rat brain.

METHODS

Adult male Sprague-Dawley rats were administered Khat (3g/kg) twice daily for 4 weeks, then underwent left middle cerebral artery occlusion (MCAO) for 2h and reperfusion for 3, 6 and 12h, respectively. The infarction area was evaluated with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Apoptosis was assessed by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL). Smac/DIABLO expression levels in experimental and control groups were examined by immunohistochemistry and Western blot.

RESULTS

Khat significantly exacerbates the neurological damage compared with control (p<0.05). In addition, Khat-treatment significantly increased the number of TUNEL-positive cells 3h (p<0.01) and 12h (p<0.05) after reperfusion. Ischemia/reperfusion enhanced the release of Smac/DIABLO from the mitochondria to the cytosol after reperfusion. Such release of Smac/DIABLO was elevated after the rats were pretreated with Khat.

CONCLUSIONS

Our results indicate that Khat treatment can induce apoptosis through enhancing the release of Smac/DIABLO from the mitochondria to the cytosol after transient focal ischemia which may be an important mechanism of Khat neurotoxicity. Therefore, Khat chewing should be avoided by people who have cerebrovascular problems.

Does khat chewing increases the risk of Mycobacterium tuberculosis infection by macrophage immune modulation?

Drug abuse is a serious problem associated with different pathological outcomes including modulating the immune system. Drug abuse is rising in Saudi Arabia and so as TB, a disease of worldwide significance, caused by immunological modulation in the host system. Khat chewing is a common practice in Arabian Peninsula which is now gaining momentum in other parts of the world. It is considered as an addiction. It has been associated with different adverse outcomes such as periodontitis, oral leukoplakia and oral cancer and also has shown to promote apoptotic cell death through cysteine proteases. The active ingredient of khat, cathinone is shown to have immunomodulatory effect. In principle, this leads to enhanced susceptibility to various infections. The present study is designed to delineate the mechanism of immunomodulation produced by khat/cathinone in human/mouse macrophage. Further, this activity will be evaluated both in vivo and in vitro in response to infection with Mycobacterium smegmatis to get an insight if there exists a co relation between the Mycobacterium tuberculosis infection and khat chewing.

Reversible khat-induced hepatitis: two case reports and review of the literature

Recreational chewing of Catha edulis (khat) leaves is part of the ethnic culture of Somali, Yemeni and other East African societies for its stimulant properties. With increasing emigration, khat use has become common in these ethnic groups once they move to other areas such as Europe and the USA; one-third of the UK Somali population report khat use within the last month. Cathinone, the active component of the khat leaves, is controlled under the UK Misuse of Drugs Act, but the use of the khat plant and its leaves remains not subject to control in the UK. There have been several previous reports of acute hepatitis related to chronic use of khat leading to acute liver failure, and resulting in transplantation or death. We report two cases with severe acute khat-related hepatitis that resolved on cessation of khat use initially, but relapsed with further use, reinforcing the importance of permanent khat cessation to prevent progression to liver failure. With reference to the current literature, we also consider the difficult diagnosis of this disorder, then go on to consider the pathophysiology, mechanisms of liver injury and potential future areas of research.

Distinct single cell signal transduction signatures in leukocyte subsets stimulated with khat extract, amphetamine-like cathinone, cathine or norephedrine

Background

Amphetamine and amphetamine derivatives are suggested to induce an immunosuppressive effect. However, knowledge of how amphetamines modulate intracellular signaling pathways in cells of the immune system is limited. We have studied phosphorylation of signal transduction proteins (Akt, CREB, ERK1/2, NF-κB, c-Cbl, STAT1/3/5/6) and stress sensors (p38 MAPK, p53) in human leukocyte subsets following in vitro treatment with the natural amphetamine cathinone, the cathinone derivatives cathine and norephedrine, in comparison with a defined extract of the psychostimulating herb khat (Catha edulis Forsk.). Intracellular protein modifications in single cells were studied using immunostaining and flow cytometry, cell viability was determined by Annexin V-FITC/Propidium Iodide staining, and T-lymphocyte proliferation was measured by ³H-thymidine incorporation.

Results

Cathinone, cathine and norephedrine generally reduced post-translational modifications of intracellular signal transducers in T-lymphocytes, B-lymphocytes, natural killer cells and monocytes, most prominently affecting c-Cbl (pTyr700), ERK1/2 (p-Thr202/p-Tyr204), p38 MAPK (p-Thr180/p-Tyr182) and p53 (both total p53 protein and p-Ser15). In contrast, the botanical khat-extract induced protein phosphorylation of STAT1 (p-Tyr701), STAT6 (p-Tyr641), c-Cbl (pTyr700), ERK1/2 (p-Thr202/p-Tyr204), NF-κB (p-Ser529), Akt (p-Ser473), p38 MAPK (p-Thr180/p-Tyr182), p53 (Ser15) as well as total p53 protein. Cathinone, cathine and norephedrine resulted in unique signaling profiles, with B-lymphocytes and natural killer cells more responsive compared to T-lymphocytes and monocytes. Treatment with norephedrine resulted in significantly increased T-lymphocyte proliferation, whereas khat-extract reduced proliferation and induced cell death.

Conclusions

Single-cell signal transduction analyses of leukocytes distinctively discriminated between stimulation with cathinone and the structurally similar derivatives cathine and norephedrine. Cathinone, cathine and norephedrine reduced phosphorylation of c-Cbl, ERK1/2, p38 MAPK and p53(Ser15), and norephedrine induced T-lymphocyte proliferation. Khat-extract induced protein phosphorylation of signal transducers, p38 MAPK and p53, followed by reduced cell proliferation and cell death. This study suggests that protein modification-specific single-cell analysis of immune cells could unravel pharmacologic effects of amphetamines and amphetamine-like agents, and further could represent a valuable tool in elucidation of mechanism(s) of action of complex botanical extracts.

Khat (Catha edulis) generates reactive oxygen species and promotes hepatic cell apoptosis via MAPK activation

A number of studies have suggested an association between khat (Catha edulis) chewing and acute liver lesions or chronic liver disease. However, little is known about the effects of khat on hepatic cells. In the current study, we investigated the mechanism behind khat-induced apoptosis in the L02 human hepatic cell line. We used cell growth inhibition assay, flow cytometry and Hoechst 33258 staining to measure hepatocyte apoptosis induced by khat. Western blot analysis was used to detect the expression levels of caspase-8 and -9, as well as those of Bax and Bcl-2. We also measured reactive oxygen species production. The results indicated that khat induced significant hepatocyte apoptosis in L02 cells. We found that khat activated caspase-8 and -9, upregulated Bax protein expression and downregulated Bcl-2 expression levels, which resulted in the coordination of apoptotic signals. Khat-induced hepatocyte apoptosis is primarily regulated through the sustained activation of the c-Jun NH2-terminal kinase (JNK) pathway and only partially via the extracellular signal-regulated kinase (ERK) cascade. Furthermore, the khat-induced reactive oxygen species (ROS) production and the activation of the ROS scavenger, N-acetyl-L-cysteine (NAC), attenuated the khat-induced activation of JNK and ERK. Our results demonstrate that khat triggers the generation of intracellular ROS and sequentially induces the sustainable activation of JNK, which in turn results in a decrease in cell viability and an increase in cell apoptosis.

Khat (Catha edulis) alters the phenotype and anti-microbial activity of peripheral blood mononuclear cells

AIMS OF STUDY

The habit of khat chewing has been associated with increased risk of systemic and oral disease. Although research has been conducted on the affects of khat on oral epithelial cells, little is known about its influence on immune cells. This study examined the biological effects of khat on the phenotype and function of peripheral blood mononuclear cells (PBMCs).

MATERIAL AND METHODS

Khat-stimulated PBMCs were examined for signs of cytotoxicity, apoptosis and changes in cell surface receptor and cytokine expression. Khat-induced regulation of transcription factors and stress-related factors were examined, as was PBMC phagocytic activity against oral bacteria.

RESULTS

Khat was cytotoxic to PBMC in a dose- and time-dependent manner and cell death was mediated by apoptosis. Khat-treated PBMC showed increased expression of co-stimulatory molecules (CD80, CD86 and MHC II) and pattern recognition receptors (TLR-2, TLR-4 and TREM-1) but secretion of inflammatory cytokines (TNFα, IL-6, CCL5, CXCL8) was inhibited. In contrast, khat induced an increase in the anti-inflammatory cytokine IL-10 as well as IL-2, IFN-γ, FasL and HSP70. These khat-induced alterations were accompanied by increased expression of transcription factors p38 MAPK and HIF-1α, whilst expression of NFκB p65 was inhibited. Although the ability of PBMC to phagocytose dextran and oral bacteria was inhibited, production of reactive oxygen species was increased.

CONCLUSION

These data suggest that khat may severely influence the effectiveness of immune surveillance and anti-microbial capacity of PBMCs.

Chemistry, pharmacology, and toxicology of khat (catha edulis forsk): a review

Catha edulis (khat) is a plant grown commonly in the horn of Africa. The leaves of khat are chewed by the people for its stimulant action. Its young buds and tender leaves are chewed to attain a state of euphoria and stimulation. Khat is an evergreen shrub, which is cultivated as a bush or small tree. The leaves have an aromatic odor. The taste is astringent and slightly sweet. The plant is seedless and hardy, growing in a variety of climates and soils. Many different compounds are found in khat including alkaloids, terpenoids, flavonoids, sterols, glycosides, tannins, amino acids, vitamins and minerals. The phenylalkylamines and the cathedulins are the major alkaloids which are structurally related to amphetamine. The major effects of khat include those on the gastro-intestinal system and on the nervous system. Constipation, urine retention and acute cardiovascular effects may be regarded as autonomic (peripheral) nervous system effects; increased alertness, dependence, tolerance and psychiatric symptoms as effects on the central nervous system. The main toxic effects include increased blood pressure, tachycardia, insomnia, anorexia, constipation, general malaise, irritability, migraine and impaired sexual potency in men. Databases such as Pubmed, Medline, Hinary, Google search, Cochrane and Embase were systematically searched for literature on the different aspects of khat to summarize chemistry, pharmacology, toxicology of khat (Catha edulis Forsk).

Cytological study of exfoliative buccal mucosal cells of Qat chewers in Yemen

Prevalence of oral cancer is relatively increasing in Yemen in recent years, which is ascribed to Qat with other carcinogens. Since the establishment of a simple and reliable method for the detection of oral cancerous and precancerous lesions is essential, exfoliative cytology (EC) was applied to a case-control study to appraise the presence and severity of oral epithelial atypia in 300 subjects (150 were Qat chewers and 150 were non-Qat users) without prior knowledge of the subjects' Qat exposure. Ten patients with oral squamous-cell carcinoma (OSCC) were included as internal controls. Cytological atypia and hyperkeratosis were demonstrated in six and 24 subjects, respectively, and could not be ascertained in the remaining 294 and 276 correspondingly. All of the 30 (six atypia and 24 hyperkeratosis) were among the 150 Qat chewers. Cytological atypia was found in all the 10 control cases with OSCCs (eight with severe degree and two with mild atypia). For the Qat among those with atypia and hyperkeratosis, the adjusted OR and the 95% confidence level were found to be 1.6 (0.8-7.2) and 3 (10.1-21.9), respectively. In view of these findings, we suggest the use of EC for detection and assessment of oral cytological atypia. Qat use contributes to the occurrence of cytological atypia that might develop to oral precancerous or cancerous lesions.

Khat Alters the Phenotype of in vitro-reconstructed Human Oral Mucosa

Khat-chewing has been associated with oral lesions including oral cancer, but the mechanisms leading to their development are not known. We hypothesized that khat interferes with the physiological processes of the oral mucosa, such as cell proliferation and differentiation, and aimed at investigating the effects of khat exposure on in vitro-reconstructed human normal buccal mucosa. Khat decreased cell proliferation, epithelial thickness, and cytokeratin 13 expression, while inducing premature expression of p21Waf1/Cip1, transglutaminases, involucrin, and filaggrin. This suggests that khat is able to induce abnormal differentiation of the buccal epithelium. Khat-induced alterations were accompanied by increased levels of p38 and were reversed by p38 inhibition, pointing to p38 as the key player in this process. The morphological changes described herein mirror the in vivo changes previously described in khat users, and demonstrate for the first time that khat induces pathological alterations in human buccal mucosa, providing evidence that raises concerns about the effects of khat use on oral health.

Camptothecin and khat (Catha edulis Forsk.) induced distinct cell death phenotypes involving modulation of c-FLIPL, Mcl-1, procaspase-8 and mitochondrial function in acute myeloid leukemia cell lines

Background

An organic extract of the recreational herb khat (Catha edulis Forsk.) triggers cell death in various leukemia cell lines in vitro. The chemotherapeutics camptothecin, a plant alkaloid topoisomerase I inhibitor, was tested side-by-side with khat in a panel of acute myeloid leukemia cell lines to elucidate mechanisms of toxicity.

Results

Khat had a profound effect on MOLM-13 cells inducing mitochondrial damage, chromatin margination and morphological features of autophagy. The effects of khat on mitochondrial ultrastructure in MOLM-13 correlated with strongly impaired routine respiration, an effect neither found in the khat-resistant MV-4-11 cells nor in camptothecin treated cells. Enforced expression of anti-apoptotic Bcl-2 protein provided protection against camptothecin-induced cell death and partly against khat toxicity. Khat-induced cell death in MOLM-13 cells included reduced levels of anti-apoptotic Mcl-1 protein, while both khat and camptothecin induced c-FLIP_L cleavage and procaspase-8 activation.

Conclusion

Khat activated a distinct cell death pathway in sensitive leukemic cells as compared to camptothecin, involving mitochondrial damage and morphological features of autophagy. This suggests that khat should be further explored in the search for novel experimental therapeutics.

Extraction and microencapsulation of khat: effects on sexual motivation and estradiol level in female rats

INTRODUCTION

Khat (Catha edulis) is an evergreen tree/shrub that is thought to affect sexual motivation or libido. Its positive effect on sexual desire is more frequently observed in females than in males and occurs when khat is chewed. Thus, khat's effects on sexual behavior may depend on the release mode of its active constituent.

AIM

This study aimed to investigate the effect of dried khat alkaloids on the sexual motivation and estradiol levels of female rats, with special emphasis on the importance of the sustained release effect.

METHODS

Dried khat leaves were extracted and isolated. The alkaloids in khat extract were identified and calculated using thin layer chromatography and high-performance liquid chromatography. The isolated khat extract was microencapsulated using a phase separation coacervation method. The morphology, particle size, yield, drug loading, and entrapment efficiency were evaluated. The in vitro release and stability of alkaloids in khat extract and in khat extract microcapsules were determined. The effect of khat extract microcapsules and varying doses of khat extract on sexual motivation in female rats were investigated. Additionally, estradiol levels, vaginal secretions and vaginal pH were determined.

MAIN OUTCOME MEASURES

The differences in the effect of khat extract and khat extract microcapsules on sexual motivation, vaginal secretion and estradiol levels in female rats were compared. Results. Cathine and norephedrine were identified in the isolated khat extract at composition of 81.3% and 17.2%, respectively. Among the formulations studied, khat extract microcapsules of formulation 2:3:5 (containing a ratio of khat extract to ovalbumin to gelatin of 2:3:5) were found to exhibit higher yield, loading, and entrapment efficiency. Khat extract microcapsules showed sustained in vitro release and were more stable than khat extract. In addition, khat extract microcapsules enhanced sexual motivation, increased vaginal secretions, and upregulated estradiol level in female rats.

CONCLUSION

The sustained release of alkaloids from dried khat has significantly enhanced the sexual motivation and increased the estradiol level of female rats. Thus the release of dried khat alkaloids from microcapsules might be an effective means of enhancing the libido in females.

Risk assessment of khat use in the Netherlands: a review based on adverse health effects, prevalence, criminal involvement and public order

In preparing a decision about the legal status of khat in the Netherlands, the Dutch Minister of Health requested CAM (Coordination point Assessment and Monitoring new drugs) to assess the overall risk of khat in the Netherlands. The present paper is a redraft of a report which formed the scientific basis of the risk evaluation procedure (October 2007). This report reviews the scientific data about khat available in the international literature. In addition, the report contains some information specific for the Netherlands (prevalence, availability of khat and public order aspects). The main psychoactive compounds in khat leaves are cathine and cathinone, which are some 2- to 10-fold less active than amphetamine. Acute health problems are rarely seen, and are usually related with malnutrition, social and financial problems. Khat has a low addictive potential. Chronic toxicity of khat is modest when used in low amounts, whereas at high levels, khat use is associated with adverse effects, like hypertension, heart rhythm disorders, insomnia and loss of appetite. In addition, khat users show a higher prevalence of cancers in the digestive tract. At population level, khat does not lead to specific health risks in the Netherlands, as its use is confined to East-African immigrants. A relationship between khat use and psychiatric disorders has been suggested, but the reports are contradictory, and such studies are presumably heavily confounded by posttraumatic and social stress. In the Netherlands (and other countries), khat use occasionally leads to minor disturbance of civil order in the public domain (loud talking, spitting), but is not related to criminal activities. Following the assessment, CAM estimated the overall risk potential of khat use in the Netherlands as very low. A similar conclusion may be drawn for countries with a comparable prevalence of khat use and khat related public order disturbance.

A review of the neuropharmacological properties of khat

BACKGROUND

The psychostimulant khat (Catha edulis Forsk), is a herbal drug cultivated and chewed as a recreational and socializing drug in East Africa and the Arabian Peninsula for centuries. Due to increasing air transportation and the loosening of customs restrictions, it is now readily available in the Western Countries mainly used by immigrants from khat growing areas causing a concern to policy-makers.

OBJECTIVE

We conducted this review to further gain an insight to the neuropharmacological effects of khat.

METHODOLOGY

PubMed search engine with key terms 'khat' or 'qat' or 'mirra' or'qaad/jaad' or 'cathinone' was used to obtain articles relevant to khat chewing. In total 284 English written articles published from 1959 to 2007 were screened.

RESULTS

Most of the studies focused on cathinone, the postulated active psychostimulant alkaloid in khat. There were few studies which investigated the entire plant extract in either in vitro or animal studies. In the majority of the studies it was reported that both cathinone and cathine, another psychoactive constituent, have actions that are similar to those of amphetamine.

CONCLUSIONS

It seems that the well investigated khat alkaloids have many features similar to amphetamines; however there is a need for a more thorough examination of khat itself in well designed in vitro, animal and human studies with a range of comparator drugs before confirming the claim that khat is a "natural amphetamine".

Genotoxic effect of Catha edulis (khat) crude extract after sub-chronic administration in rats

The aim of this study was to evaluate the genotoxic effects of a crude extract of khat (Catha edulis, Forsk) leaves in rats. Two groups were fed khat crude extract, 1000 and 2000mg/kg body weight, for 90 days and were compared with a control group. The alkaline (pH>13) version of comet assay was used in this study. However, no previous published work has been undertaken and showed the effect of khat on DNA migration in the comet assay. To compare the comet assay results with another genetic endpoint, blood samples were analyzed for chromosomal aberrations. These results showed no DNA damage detected using comet assay in both the khat treated groups, while the results of chromosomal aberrations assay showed a significant increase (P<0.05) in the 2000mg/kg body weight treated group compared to the control group.

Khat induces G1-phase arrest and increased expression of stress-sensitive p53 and p16 proteins in normal human oral keratinocytes and fibroblasts

Khat is a psychostimulant plant used by over 10 million people daily, mainly in eastern Africa and the Middle East. Previous studies have suggested an association between khat use and oral lesions such as hyperkeratosis and oral cancer. This study investigated the effects of an extract of khat on primary normal human oral keratinocytes (NOK) and normal human oral fibroblasts (NOF). Low (sublethal) concentrations of khat inhibited the proliferation of both cell types in a dose-dependent and time-dependent manner. Both NOK and NOF treated with khat accumulated in the G1-phase of the cell cycle and showed increased expression of the stress-sensitive p53 protein after 24 h. Normal human oral keratinocytes showed a profound increase in p16(INK4A) (p16) after 24 h and showed morphological changes suggesting cell differentiation. Normal human oral fibroblasts showed growth inhibition and increased expression of p21(WAF1/CIP1) (p21) within 24 h. The concentrations of khat tested in this study were within the range of those found in the oral cavity of khat chewers. The results show that stress induced by khat modulates the cell cycle in oral keratinocytes and fibroblasts. It is further speculated whether khat could have similar effects in vivo, especially in keratinocytes.

Khat (Catha edulis) induces reactive oxygen species and apoptosis in normal human oral keratinocytes and fibroblasts

Khat chewing is widely practiced in Eastern Africa and the Middle East. Khat is genotoxic to cells within the oral mucosa, and several studies have suggested an association between khat use and oral lesions like hyperkeratosis and oral cancer. This study investigated the mechanism of khat-induced cytotoxicity using primary normal human oral keratinocytes (NOK) and fibroblasts (NOF). Khat induced rounding up of cells, plasma membrane blebbing, and condensation of nuclear chromatin within 3-6 h of exposure. The cells also showed externalization of phosphatidylserine and fragmentation of DNA. Morphological and biochemical features were compatible with cell death by apoptosis. Khat also induced an increase in cytosolic reactive oxygen species (ROS) and a depletion of intracellular glutathione (GSH) within 1 h of exposure. Antioxidants reduced ROS generation, GSH depletion and delayed the onset of cytotoxicity in both cell types. Generally, NOF cells were more sensitive to khat-induced cytotoxicity than NOK cells. These effects were elicited at concentrations of khat expected to occur in the oral cavity during khat chewing. In summary, khat induced apoptotic cell death in primary normal oral keratinocytes and fibroblasts by an early effect on mechanisms that regulate oxidative stress.

Khat chewing from the pharmacological point of view: an update

Khat chewing is deeply rooted in the every day life of people living in the Horn of Africa and in South Arabia, where Catha edulis is endemic. Considered little more than an exotic habit producing just mild pharmacological effects, systematic investigations on its active principles have instead lead to the isolation and chemical characterization of cathinone, a compound structurally related to amphetamine. Three decades of intense experimental and clinical research on khat have depicted a consistently clear picture of its pharmacological and toxicological effects.

Stress-induced in vitro apoptosis of native human acute myelogenous leukemia (AML) cells shows a wide variation between patients and is associated with low BCL-2:Bax ratio and low levels of heat shock protein 70 and 90

Spontaneous in vitro apoptosis reflects a true biological heterogeneity between patients which has to be considered when in vitro models are used to study regulation of apoptosis in native human AML cells. Even though the balance between pro- and anti-apoptotic signaling seems to have a prognostic impact in AML, the possible clinical relevance of spontaneous apoptosis remains to be clarified. High apoptosis/low viability was associated with low levels of heat shock proteins 70 and 90 as well as low Bcl-2:Bax ratio for patients heterogeneous with regard to morphology, membrane molecule expression, genetic abnormalities and response to therapy.

The potential adverse effects of habitual use of Catha edulis (khat)

The habit of Catha edulis Forsk (khat) chewing has prevailed for centuries among populations in the horn of Africa and the Arabian peninsula. Fresh leaves of Catha edulis are customarily chewed to attain a state of stimulation. The fact that cathinone has a closer structural similarity with amphetamine, and both share common pharmacodynamic features, led to the conclusion that cathinone is the most important active ingredient of Catha edulis, which causes the major pharmacological effects. Problems associated with repeated consumption of Catha edulis leaves are becoming evident. Literature surveys and clinical diagnostic studies revealed an association with prevalence of psychiatric morbidity. Repeated intermittent oral administration of Catha edulis to laboratory animals lead to development and expression of locomotor sensitisation. Catha edulis also leads to several peripheral effects that include increases in blood pressure and has been associated with the increased incidence of acute coronary vasospasm and myocardial infarction. Catha edulis also accounts for a number of gastrointestinal tract problems, oesophagitis, gastritis and delay intestinal absorption, as well as the development of oral keratotic white lesions at the site of chewing. Administration of Catha edulis extracts showed a deranged systemic capacity to handle oxidative radicals and induces cytotoxic effects in cells of liver and kidney, as well as induction of cell death in various human leukaemia cell lines and in peripheral human blood leukocytes.