NAPHTHOQUINONE DERIVATIVES AND THEIR USE IN THE TREATMENT AND CONTROL OF TUBERCULOSIS

Abstract: Naphthoquinone derivatives of Formula (1): wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether; R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; R2 and R3 each independently represent hydrogen or a group selected from: (A), (B), or (C) wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; R4 represents hydrogen or a group selected from: (D), (E) or (F) wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; or pharmaceutically acceptable salts thereof, are useful for the treatment and/or control of a tuberculosis in a patient caused by <i>Mycobacterium tuberculosis</i>.

Description: NAPHTHOQUINONE DERIVATIVES AND THEIR USE IN THE TREATMENT AND CONTROL OF TUBERCULOSIS BACKGROUND OF THE INVENTION THIS invention relates to the treatment and control of tuberculosis caused by Mycobacteπum tuberculosis and in particular to the use of naphthoquinone derivatives in such treatment and control Tuberculosis (TB) remains a serious health problem in many regions of the world, especially in developing nations It is a contagious disease and is becoming epidemic in some parts of the world It is estimated that 30-60% of adults in developing countries are infected with Mycobactenum tuberculosis Approximately 8-10 million individuals develop clinical TB and 3 million die of TB each year (WHO/IUATLD, 1989) In South Africa, over 3 in every thousand people die of TB, the highest rate in the world, while one out of every 200 people suffers from active tuberculosis Tuberculosis is the most commonly notified disease in South Africa and the fifth largest cause of death among the black population (South African Tuberculosis Association, 1998) In the United States, the number of TB cases steadily decreased until 1986 when an increase was noted Since then TB cases have continued to rise Ten million individuals are infected in the U S A , with approximately 26000 new cases of active disease each year (National Jewish Medical and Research Center, 1994) Individuals infected with Human Immunodeficiency Virus (HIV) are very susceptible to tuberculosis and often develop this disease before other manifestations of AIDS become apparent (Grange and Davey, 1990) Control of the TB epidemic linked with HIV infection will depend largely on the adequate treatment of TB, and possibly of effective chemoprophylaxis, not just for HIV-infected persons but for communities as well (WHO/I UATLD, 1989) TB therapy has been revolutionized and the present treatment regimes for TB are based on multidrug therapy with usually 3 or 4 antituberculosis drugs However, the problem of multidrug resistant tubercle bacilli is emerging for various drugs such as isoniazid, ethambutol, πfampicin and streptomycin, for example (Girling, 1989, Grange and Davey, 1990) Drug- resistant TB is very difficult to treat requiring greater numbers and varieties of medications for a longer period of treatment The need for new antituberculosis agents is urgent due to the increasing resistance of mycobacteπa to these classic antituberculosis drugs A recent WHO report states that, globally, 2% of all cases of tuberculosis are multidrug resistant - by definition, resistance to πfampicin plus isoniazid (plus/minus other resistances) Such cases can be treated in the USA and other high resource regions but at a great cost (> US$ 250,000 per case 1 ) and using very long courses of rather toxic drugs, thereby raising serious problems of compliance (WHO, 1997) South Africa is witnessing an explosion in the number of cases of drug-resistant tuberculosis In some parts of South Africa, 1 in 10 cases of TB is resistant to treatment (New Scientist, March 1997) it is essential to have new antituberculosis agents, preferably those that can readily and simply be produced from some local source SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a naphthoquinone derivative of Formula 1 wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether, R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R2 and R3 each independently represent hydrogen or a group selected from wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R4 represents hydrogen or a group selected from wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, or pharmaceutically acceptable salts thereof, for use in a method of treating and/or controlling tuberculosis in a patient caused by Mycobactenum tuberculosis According to a second aspect of the invention there is provided the use of a naphthoquinone derivative having the Formula 1 as set out above in the manufacture of a medicament for use in a method of treating and/or controlling tuberculosis in a patient caused by Mycobactenum tuberculosis According to a third aspect of the invention there is provided a method of treating and/or controlling tuberculosis caused by Mycobactenum tuberculosis comprising administering to a patient in need thereof an effective amount of a naphthoquinone derivative having the Formula 1 as set out above The naphthoquinone derivative of Formula 1 is typically a compound of Formula 1 a or Formula 1 b Formula 1a Formula 1 b wherein R and R1 are as defined for Formula 1 above. R in the compound of Formula 1 a or 1 b is preferably an OH group. R1 in the compound of Formula 1 a or 1 b is preferably a CH 3 group. In particular, the naphthoquinone derivative of Formula 1 is 5,5' dihydroxy 7,7' binaphthoquinone (diospyrin) or 5-hydroxy-7-methyl-1 ,4-naphtoquinone (methyljuglone). DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is directed at the use of naphthoquinone derivatives in the treatment and/or control of tuberculosis caused by Mycobactenum tuberculosis: In particular, naphthoquinone derivatives of the general Formula 1 wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether; R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; R2 and R3 each independently represent hydrogen or a group selected from: wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R4 represents hydrogen or a group selected from wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, have been found to be effective against Mycobactenum tuberculosis Particular naphthoquinone derivatives of Formula 1 a and 1 b have been found to be particularly effective Formula 1 a Formula 1b In particular diospynn and methyljuglone, naphthoquinone derivatives of Formula 1 a and Formula 1 b, respectively, in which R is OH and R1 is a methyl group, have been found to inhibit several antibiotic resistant as well as antibiotic susceptible strains of Mycobactenum tuberculosis Although diospynn and methyljuglone are particularly preferred, naphthoquinone derivatives of Formula 1a and 1 b in which R is a methyl ether, ethyl ether or similar ether and R1 is an ethyl or similar aliphatic hydrocarbon derivative are also provided An extensive research program was undertaken in order to identify antituberculosis agents that can readily and simply be produced from local resources Twenty South African medicinal plants used to treat pulmonary diseases were screened for activity against drug-resistant and sensitive strains of M tuberculosis A preliminary screening of acetone and water plant extracts, against a drug-sensitive strain of M tuberculosis, H37Rv, was carried out by the agar plate method Fourteen of the 20 acetone extracts showed inhibitory activity at a concentration of 0 5 mg/ml against this strain Acetone as well as water extracts of Cryptocarya latifolia, Euclea natalensis, Helichrysum melanacme, Nidorella anomala and Thymus vulgans inhibited the growth of M tuberculosis Given the activity of 14 acetone extracts at 0 5 mg/ml against the drug-sensitive strain by the agar plate method a further study was carried out employing the rapid radiometric method to confirm the inhibitory activity These active acetone extracts were screened against the H37Rv strain as well as a strain resistant to the drugs, isoniazid and πfampicin The minimal inhibitory concentration of Croton pseudopulchellus, Ekebergia capensis, Euclea natalensis, Nidorella anomala and Polygala myrtifolia was 0 1 mg/ml against the H37Rv strain by the radiometric method Extracts of Chenopodium ambrosioides, Ekebergia capensis, Euclea natalensis, Helichrysum melanacme, Nidorella anomala and Polygala myrtifolia were active against the resistant strain at 0 1 mg/ml Eight plants showed activity against both the strains at a concentration of 1 0 mg/ml The following procedure was developed by the applicant for the isolation of diospynn and methyljuglone from E natalensis and other species in this genus, as well as any other plants that may synthesise diospynn or methyljuglone or other quinone derivatives 1. Identification of plant species Roots and the aerial plant parts of E natalensis were collected near Durban and identified at the HGWJ Schweickerdt Herbarium of the University of Pretoria and also at the herbarium of the National Botanical Institute, Pretoria 2. Extraction Dried roots of E natalensis were ground to a powdery form with a dry mill and extracted over 48 hours with acetone The extract was filtered and concentrated to dryness at reduced pressure on a rotary evaporator 3. Thin layer chromatography A direct antibacterial bioassay (Dilika & Meyer 1996) on TLC-plates was employed to speedup the activity guided isolation of the antituberculosis compounds M tuberculosis cannot be tested in this way because of its very slow growth rate The direct antibacterial bioassays of the acetone extract were done on TLC plates (Merck) developed with chloroform-hexane (1 1 ) After development, the TLC plates were dried and sprayed with a 24 hr old Staphylococcus aureus culture in nutrient broth After 24 hr incubation, the plates were sprayed with an aqueous solution of 2mg/ml p-iodonitrotetrazohum violet to visualise the bacterial cells The plates were then reincubated at 37°C for 2-3 hours Two zones of bacterial growth inhibition could be seen on TLC plates sprayed with S aureus Activity was more pronounced in the R f 0 30 zone (chloroform-hexane (1 1 )) than in the R f 0 54 zone Column chromatography The crude extract of the plant was dried, its mass determined and resuspended in chloroform Column chromatography was performed on silica gel 60 using chloroform as eluent The antibacterial fractions collected were then subjected to a Sephadex LH-20 column chromatography using ethanol as eluent The fractions collected were again tested for antibacterial activity on TLC to detect the fractions containing the active compounds of R f 0 30 and R f 0 54 High performance liquid chromatography The compounds were further purified by HPLC utilising an analytical Phenomenex reverse phase 250x4 60 mm column, at a flow rate of 1 0 ml/mm, oven temp 40°C and a wavelength of 206nm An ethanol-water (50 50) solution was employed as mobile phase The pure compounds were once again subjected to a Sephadex LH-20 column chromatography and proved to be pure The chemical structures were confirmed by 1 H and 3 C nmr and ms to be Diospynn (5,5' dihydroxy 7,7' binaphthoquinone), C 22 H 14 O 6 Molecular weight 374 35 7-methyljuglone (5-hydroxy-7-methyl-1 4-naphtoquιnone), CnH 8 0 3 Molecular weight 188 19 The effect of diospynn and methyljuglone on the growth of the sensitive strain (H37Rv) and resistant strains of Mycobactenum tuberculosis as determined by the radiometric method are set out in Table 1 and Table 2 TABLE 1 Effect of diospynn on the growth of the sensitive strain (H37Rv) and resistant strains of Mycobactenum tuberculosis as determined by the radiometric method a ΔGI values are means ± s d TABLE 2 Effect of 7-methyljuglone as a single agent and in combination with diospynn on the growth of the sensitive strain (H37Rv) and resistant strains of Mycobactenum tuberculosis as determined by the radiometric method Mιnιmal inhibitory concentration ΔGI values are means ± s d The results show that diospynn and methyljuglone control the Mycobactenum tuberculosis bacterium effectively Oral administration of diospynn or methyljuglone in an appropriate pharmaceutical composition with suitable diluents and carriers will typically be used to treat or control tuberculosis This will be by way of tablet, liquid or similar oral dosage form, as diospynn and methyljuglone are readily absorbed intestinally However, it is believed that diospynn or methyljuglone administered intravenously or intramuscularly will also be absorbed effectively through blood vessels and the blood stream of a patient Transdermal administration, via a plaster or similar transdermal administration vehicle, is also a possibility A combination treatment of diospynn and methyljuglone, which may be more effective than singular treatments of the two naphthoquinones, is also envisaged The applicant believes that it may be possible to increase the concentration of diospynn, methyljuglone and other qumones in £ natalensis or similar species by phytoalexic stimulation or by the biotechnological manipulation of tissue cultures and/or intact plants Qumones are generally synthesised from catechol (1 ,2-quιnones) or hydroqumone (1 ,4-quιnones) by mild oxidation Catechol Hydioquinone As far as the applicant has been able to establish, diospynn has been synthesised once in a laboratory (Yoshida, M and Mori, K 2000 European Journal of Organic Chemistry pages 1313 - 1317) However, similar binapthoquinones can also be synthesised by the reaction of plumbagin (94mg in methanol, 10ml) and its hydroqumone (190mg in methanol 14ml), buffered in phosphate to pH 6 8 at 30°C (Sankaram et al 1975, Kuman et al 1982) Plumbagin It is believed that diospynn, methyljuglone and related naphthoquinone derivatives are viable alternatives to conventional drugs in the treatment and control of tuberculosis in humans

Claims: CLAIMS 1. A naphthoquinone derivative of Formula 1 : wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether; R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; R2 and R3 each independently represent hydrogen or a group selected from: wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; R4 represents hydrogen or a group selected from: wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative; or pharmaceutically acceptable salts thereof, for use in a method of treating and/or controlling tuberculosis in a patient caused by Mycobactenum tuberculosis 2 A naphthoquinone derivative of Formula 1 according to claim 1 which is a compound of Formula 1 a or Formula 1 b Formula 1a wherein R and R1 are as defined for Formula 1 in claim 1 3 A naphthoquinone derivative according to claim 2 wherein R is an OH group 4 A naphthoquinone derivative according to claim 2 or claim 3 wherein R1 is a CH 3 group 5 A naphthoquinone derivative of Formula 1 according to claim 1 which is 5,5' dihydroxy 7,7' binaphthoquinone (diospynn) or 5-hydroxy-7-methyl-1 ,4- naphtoquinone (methyljuglone), or a mixture thereof 6 The use of a naphthoquinone derivative having the Formula 1 wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether, R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R2 and R3 each independently represent hydrogen or a group selected from wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R4 represents hydrogen or a group selected from wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, or pharmaceutically acceptable salts thereof, in the manufacture of a medicament for use in a method of treating and/or controlling tuberculosis in a patient caused by Mycobactenum tuberculosis 7. The use according to claim 6 wherein the naphthoquinone derivative of Formula 1 is a compound of Formula 1a or Formula 1 b' Formula 1 a Formula 1 b wherein R and R1 are as defined for Formula 1 in claim 6. 8. The use according to claim 7 wherein R is an OH group. 9. The use according to claim 7 or claim 8 wherein R1 is a CH 3 group. 10. The use according to claim 6 wherein the naphthoquinone derivative of Formula 1 is 5,5' dihydroxy 7,7' binaphthoquinone (diospynn) or 5-hydroxy- 7-methyl-1 ,4-naphtoquinone (methyljuglone), or a mixture thereof. 1 1 A method of treating and/or controlling tuberculosis caused by Mycobactenum tuberculosis comprising administering to a patient in need thereof an effective amount of a naphthoquinone derivative having the Formula 1 wherein, R represents an OH group, methyl ether, ethyl ether or a similar ether, R1 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R2 and R3 each independently represent hydrogen or a group selected from wherein R5 represents an OH group, methyl ether, ethyl ether or a similar ether and R6 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, R4 represents hydrogen or a group selected from wherein R7 represents an OH group, methyl ether, ethyl ether or a similar ether and R8 represents a methyl, ethyl or similar aliphatic hydrocarbon derivative, or pharmaceutically acceptable salts thereof 12 A method according to claim 1 1 wherein the naphthoquinone derivative of Formula 1 is a compound of Formula 1a or Formula 1 b Formula 1 a Formula 1 b wherein R and R1 are as defined for Formula 1 in claim 11 13 A method according to claim 12 wherein R is an OH group 14 A method according to claim 12 or claim 13 wherein R1 is a CH 3 group. 15. A method according to claim 1 1 wherein the naphthoquinone derivative of Formula 1 is 5,5' dihydroxy 7,7' binaphthoquinone (diospynn) or 5- hydroxy-7-methyl-1 ,4-naphtoquιnone (methyljuglone), or a mixture thereof 16. A method according to claim 11 wherein the naphthoquinone derivative of Formula 1 is administered orally, intravenously, intramuscularly or transdermally.

Inventors: LALL NAMRITA, MEYER JACOBUS JOHANNES MARION, LALL, NAMRITA, MEYER, JACOBUS, JOHANNES, MARION
Applicants: LALL NAMRITA, MEYER JACOBUS JOHANNES MARION, UNIV PRETORIA, LALL, NAMRITA, MEYER, JACOBUS, JOHANNES, MARION, UNIVERSITY OF PRETORIA
Application year: 2000
Main classification: C07C50
IPC codes: A61K31, A61P31, C07C50