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Bioassay-guided fractionation of the chloroform extract of Byrsonima fagifolia leaves led to the isolation of active antitubercular compounds alkane dotriacontane (Minimal Inhibitory Concentration—MIC, 62.5 μgmL-1), triterpenoids as bassic acid (MIC = 2.5 μgmL-1), α-amyrin acetate (MIC = 62.5 μgmL-1), a mixture of lupeol, α- and β-amyrin (MIC = 31.5 μgmL-1) and a mixture of lupeol, and acetates of α- and β-amyrin (MIC = 31.5 μgmL-1). The antimycobacterial activity was determined by the Microplate Alamar Blue Assay (MABA) and the structures of promising compounds were determined by spectroscopic analysis. This investigation constitutes the first report of a chemical and antitubercular study of apolar compounds from B. fagifolia Niedenzu (IK). [ABSTRACT FROM AUTHOR]

Objectives: The most recent survey conducted by the World Health Organization described Tuberculosis (TB) as one of the top 10 causes of death and the leading cause of death from a single infectious agent. The increasing number of TB-resistant cases has contributed to this scenario. In light of this, new strategies to control and treat the disease are necessary. Our research group has previously described furoxan derivatives as promising scaffolds to be explored as new antitubercular drugs., Results: Two of these furoxan derivatives, (14b) and (14c), demonstrated a high selectivity against Mycobacterium tuberculosis. The compounds (14b) and (14c) were also active against a latent M. tuberculosis strain, with MIC 90 values of 6.67 μM and 9.84 μM, respectively; they were also active against monoresistant strains (MIC 90 values ranging from 0.61 to 20.42 μM) and clinical MDR strains (MIC 90 values ranging from 3.09 to 42.95 μM). Time-kill experiments with compound (14c) showed early bactericidal effects that were superior to those of the first- and second-line anti-tuberculosis drugs currently used in therapy. The safety of compounds (14b) and (14c) was demonstrated by the Ames test because these molecules were not mutagenic under the tested conditions. Finally, we confirmed the safety, and high efficacy of compounds (14b) and (14c), which reduced M. tuberculosis to undetectable levels in a mouse aerosol model of infection., Conclusion: Altogether, we have identified two advanced lead compounds, (14b) and (14c), as novel promising candidates for the treatment of TB infection., (Copyright © 2020. Published by Elsevier Masson SAS.)

Context: Whether natural product drug discovery programs should rely on wild plants collected "randomly" from the natural environment, or whether they should also include plants collected on the basis of use in traditional medicine remains an open question., Objective: This study analyzes whether plants with ethnomedical uses from Vietnam and Laos have a higher hit rate in bioassay testing than plants collected from a national park in Vietnam with the goal of maximizing taxonomic diversity ("random" collection)., Materials and Methods: All plants were extracted and subjected to bioassay in the same laboratories. Results of assays of plant collections and plant parts (samples) were scored as active or inactive based on whether any extracts had a positive result in a bioassay. Contingency tables were analyzed using χ(2) statistics., Results: Random collections had a higher hit rate than ethnomedical collections, but for samples, ethnomedical plants were more likely to be active. Ethnomedical collections and samples had higher hit rates for tuberculosis, while samples, but not collections, had a higher hit rate for malaria. Little evidence was found to support an advantage for ethnomedical plants in HIV, chemoprevention and cancer bioassays. Plants whose ethnomedical uses directly correlated to a bioassay did not have a significantly higher hit rate than random plants., Discussion: Plants with ethnomedical uses generally had a higher rate of activity in some drug discovery bioassays, but the assays did not directly confirm specific uses., Conclusions: Ethnomedical uses may contribute to a higher rate of activity in drug discovery screening.

Clinical utility of rifabutin 1 (RBT), a potent antibiotic used in multidrug regimens for tuberculosis (TB) as well as for infections caused by Mycobacterium avium complex (MAC), has been hampered due to dose-limiting toxicity. RBT analogs 2-11 were synthesized and evaluated against M. avium 1581 and Mycobacterium tuberculosis susceptible and resistant strains in vitro. A selection of candidates were also assayed against non-replicating persistent (NRP) M. tuberculosis. Subsequent in vivo studies with the best preclinical candidate drugs 5 and 8, in a model of progressive pulmonary tuberculosis of Balb/C mice infected either with H(37)Rv drug-sensible strain or with multidrug resistant (MDR) clinical isolates, resistant to all primary antibiotics including rifampicin, were performed. The results disclosed here suggest that 5 and 8 have potential for clinical application.

The recent increase in the incidence of tuberculosis with the emergence of multidrug-resistant (MDR) cases has lead to the search for new drugs that are effective against MDR strains of Mycobacterium tuberculosis and can augment the potential of existing drugs against tuberculosis. In the present study, we investigated the activities of a naphthoquinone, 7-methyljuglone, isolated from the roots of Euclea natalensis alone and in combination with other antituberculous drugs against extracellular and intracellular M. tuberculosis. Combinations of 7-methyljuglone with isoniazid or rifampicin resulted in a four to six-fold reduction in the minimum inhibitory concentration of each compound. Fractional inhibitory concentration (FIC) indexes obtained were 0.2 and 0.5, respectively, for rifampicin and isoniazid, suggesting a synergistic interaction between 7-methyljuglone and these anti-TB drugs. The ability of 7-methyljuglone to enhance the activity of isoniazid and rifampicin against both extracellular and intracellular organisms suggests that 7-methyljuglone may serve as a promising compound for development as an anti-tuberculous agent.

A rapid and accurate antimycobacterial susceptibility test is essential for effective treatment of tuberculosis. The aim of this study was to evaluate a modified method applying 2,3-diphenyl-5-thienyl-(2)-tetrazolium chloride (STC) to the Clinical and Laboratory Standards Institute (CLSI) guideline for susceptibility testing of Mycobacterium tuberculosis. A total of 132 clinical isolates of M. tuberculosis, forty-eight isolates showing resistance to one or more of the first-line antituberculosis drugs, and eighty-four fully susceptible isolates were collected from hospitals of a nationwide distribution from June to September 2004. The modified procedure was conducted basically according to the agar-proportion method described in the CLSI Guideline both with STC 50 mug/mL. The amount of growth in each well was recorded and graded at 2nd and 3rd weeks after inoculation. After 3 weeks of incubation, the diagnostic sensitivity and specificity for the detection of drug-resistant strains of STC-containing agar proportion methods were 100%, except ethambutol-low level resistance, of which the diagnostic sensitivity was 93.4%. After two weeks of incubation in STC-containing agar proportion methods, one hundred of the 107 strain-drug combinations have shown drug resistance, indicating the sensitivity of 93.5%. Especially, all 41 isoniazid-resistant strains and 19 of 21 rifampin-resistant strains (90.5%) could be detected after two weeks of incubation. A modification of the agar proportion method using STC resulted in a reliable and more easily interpretable data, and detected most of resistant strains a week earlier than conventional method.

Ethnobotany/ethnopharmacology has contributed to the discovery of many important plant-derived drugs. Field explorations to seek and document indigenous/traditional medical knowledge (IMK/TMK), and/or the biodiversity with which the IMK/TMK is attached, and its conversion into a commercialized product is known as bioprospecting or biodiversity prospecting. When performed in a large-scale operation, the effort is referred to as mass bioprospecting. Experiences from the mass bioprospecting efforts undertaken by the United States National Cancer Institute, the National Cooperative Drug Discovery Groups (NCDDG) and the International Cooperative Biodiversity Groups (ICBG) programs demonstrate that mass bioprospecting is a complex process, involving expertise from diverse areas of human endeavors, but central to it is the Memorandum of Agreement (MOA) that recognizes issues on genetic access, prior informed consent, intellectual property and the sharing of benefits that may arise as a result of the effort. Future mass bioprospecting endeavors must take heed of the lessons learned from past and present experiences in the planning for a successful mass bioprospecting venture.

Naphthoquinones and triterpenes isolated from the roots of Euclea natalensis. A.DC (Ebenaceae) were evaluated for their inhibitory activity against Mycobacterium tuberculosis.. Crude extract, diospyrin and 7-methyljuglone isolated from the plant, exhibited minimum inhibitory concentrations of 8.0, 8.0, and 0.5 µg ml -1 , respectively, against M. tuberculosis. H37 Rv (ATCC 27294), a drug-sensitive strain. Minimum inhibitory concentrations (MICs) of 7- methyljuglone against a panel of clinical pan-sensitive and drug-resistant strains of M. tuberculosis. ranged from 0.32 to 1.25 µg/ml. The concentration of 7-methyljuglone that effected a 90% reduction of growth of M. tuberculosis. Erdman within J774.1 macrophages was 0.57 µg/ml. The superior intracellular and extracellular inhibition of M. tuberculosis. by 7-methyljuglone relative to that of the antituberculosis drugs streptomycin and ethambutol suggests that this compound be considered as a lead for further investigations.

Crude extracts of Haplopappus sonorensis (A. Gray) S.F. Blake (Asteraceae), showed activity against Mycobacterium tuberculosis H(37)Rv. By assay-guided fractionation, 5-hydroxy-3,7,4'-trimethoxyflavone (1). 5,7-dihydroxy-3,4'-dimethoxyflavone (2). and 5,4'-dihydroxy-3,7-dimethoxyflavone (3). were identified as the antimycobacterial principles. Compound 2 was the most active compound.

The MTT method for rifampicin and isoniazid susceptibility testing of Mycobacterium tuberculosis was developed by using bacterial suspension prepared from colonies on solid media. The MTT tube assay in 1 ml Middlebrook 7H9 broth was completed within 4 days for rifampicin (RMP) and within 7 days for isoniazid (INH). When MTT assay results with 279 M. tuberculosis clinical isolates were compared with those of the conventional proportion method on Löwenstein-Jensen medium, high specificity and sensitivity values of 100% and 94.1%, respectively, for RMP susceptibility testing, and 99.5% and 89.2%, respectively, for INH susceptibility testing were obtained. The accuracy of the MTT method for RMP and INH was > 0.97 concordance with the proportion method. The MTT method is simple, inexpensive and rapid. The high level of agreement with the conventional proportion method suggests a potential to rapidly detect drug-resistant M. tuberculosis in developing countries, as only basic microbiological equipment is need.

Abstract. Tuberculosis (TB), mainly caused by Mycobacterium tuberculosis, is the leading killer among all infectious diseases worldwide and is responsible for more than two million deaths annually. For over thirty years no antitubercular agents with new mechanisms of action have been developed. The recent increase in the number of multi-drug resistant clinical isolates of M. tuberculosis has created an urgent need for the discovery and development of new antituberculosis leads. This review covers recent reports on plant-derived terpenoids that have demonstrated moderate to high activity in in vitro bioassays against M. tuberculosis. In this review, mono-, sesqui-, di- and triterpenes, and sterols, their structural analogs and semisynthetic derivatives will be discussed, with particular emphasis on the structural features essential for antimycobacterial activity.

Dicationic 2,5-bis(4-guanidinophenyl)furans 5a-5f, 2,5-bis[4-(arylimino)aminophenyl]furans 6a-6b and 6e-6k, and 2,5-bis[4-(alkylimino)aminophenyl]furans 6c-6d have been synthesized starting from 2,5-bis[tri-n-butylstannyl]furan. Thermal melting studies with poly dA*dT and the duplex oligomer d(CGCGAATTCGCG)2 demonstrated high DNA binding affinities for a number of the compounds. The binding affinities are highly dependent on structure and are significantly affected by substituents both on the phenyl rings of the 2,5-diphenylfuran nucleus and on the cationic centers. Of the 17 novel dicationic compounds synthesized, six (6a, 6b, 5b, 6f, 6h, 6i) exhibited MICs of 2 microg/mL or less versus Mycobacterium tuberculosis. Of the compounds screened against Candida albicans, three gave MICs of 2 microg/mL or less (5b, 6h, 6i), and two (5b, 6i) were fungicidal, unlike a standard antifungal drug fluconazole, which was fungistatic. In addition, one of the tested compounds (6i) exhibited a MIC of <1 microg/mL against Aspergillus fumigatus, while also being a fungicidal against this organism. Finally, when evaluated against an expanded fungal panel, compound 6h showed good activity against Cryptococcus neoformans and Rhizopus arrhizus.

An L-rhamnosyl residue plays an essential structural role in the cell wall of Mycobacterium tuberculosis. Therefore, the four enzymes (RmlA to RmlD) that form dTDP-rhamnose from dTTP and glucose-1-phosphate are important targets for the development of new tuberculosis therapeutics. M. tuberculosis genes encoding RmlA, RmlC, and RmlD have been identified and expressed in Escherichia coli. It is shown here that genes for only one isotype each of RmlA to RmlD are present in the M. tuberculosis genome. The gene for RmlB is Rv3464. Rv3264c was shown to encode ManB, not a second isotype of RmlA. Using recombinant RmlB, -C, and -D enzymes, a microtiter plate assay was developed to screen for inhibitors of the formation of dTDP-rhamnose. The three enzymes were incubated with dTDP-glucose and NADPH to form dTDP-rhamnose and NADP(+) with a concomitant decrease in optical density at 340 nm (OD(340)). Inhibitor candidates were monitored for their ability to lower the rate of OD(340) change. To test the robustness and practicality of the assay, a chemical library of 8,000 compounds was screened. Eleven inhibitors active at 10 microM were identified; four of these showed activities against whole M. tuberculosis cells, with MICs from 128 to 16 microg/ml. A rhodanine structural motif was present in three of the enzyme inhibitors, and two of these showed activity against whole M. tuberculosis cells. The enzyme assay was used to screen 60 Peruvian plant extracts known to inhibit the growth of M. tuberculosis in culture; two extracts were active inhibitors in the enzyme assay at concentrations of less than 2 microg/ml.

A series of mainly marine derived natural products were tested for their activities against Mycobacterium tuberculosis and M. avium. Of the thirty-nine compounds tested fifteen demonstrated minimum inhibition concentrations (MICs) of 32 micrograms/ml or less, and eleven had MICs of 16 micrograms/ml or less. The most active compound found in this study was the sponge derived metabolite axisonitrile-3 (MIC 2 micrograms/ml).

In a bioassay-guided search for antimycobacterial natural products from higher plants, we have chemically investigated the methanol extract of aerial parts of Ajuga remota Benth. (Labiatae) for its active constituent(s). Bioactive chromatographic fractions of the crude extract provided the known triterpene ergosterol-5,8-endoperoxide plus the diterpenes clerodin, ajugarin-I, and ajugarin-II, which had been previously isolated from A. remota. This is the first report on the isolation of ergosterol-5,8-endoperoxide from this plant. The above compounds were tested in a radiorespirometric bioassay for activity against Mycobacterium tuberculosis. Ergosterol-5,8-endoperoxide showed a minimum inhibitory concentration (MIC) of 1 microgram/ml, while ergosterol-5,8-endoperoxide acetate, ergosterol, and ergosta-5,7,9(11),22-tetraen-3 beta-ol gave MICs of 8 micrograms/ml, > 128 micrograms/ml, and 128 micrograms/ml, respectively. Clerodin, ajugarin-I, and ajugarin-II were inactive with MICs of > 128 micrograms/ml.

Screening of plants from South America for antitubercular activity and subsequent assay-guided fractionation resulted in the isolation and characterization of several pentacyclic triterpenoids. The MIC values of 22 triterpenoids were determined using the radiorespiratory BACTEC assay and range from 8 microM to above 128 microM. The structure-activity relationships are discussed.

Bioassay-directed fractionation of the organic extract of the Kenyan pyrethrum flowers (Chrysanthemum cinerariaefolium Vissiani) resulted in the isolation of two natural pyrethrin esters, pyrethrin I (PI) and pyrethrin II (PII) as the major constituents. These esters elicited inhibition of the multiple drug resistant (MDR) Mycobacterium tuberculosis. The high-field (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of PI and PII were unequivocally assigned using modern two-dimensional (2D) proton-detected heteronuclear multiple-quantum coherence (HMQC) and heteronuclear multiple-bond correlation (HMBC) experiments. The conformations of both esters were deduced from (1)H-(1)H vicinal coupling constants and confirmed by 2D nuclear Overhauser effect spectroscopy (NOESY). Computer molecular modeling (MM) studies revealed that PI and PII molecules adopt a "love-seat" conformation in chloroform (CDCl(3)) solution.

The therapeutic efficacy of liposomal clofazimine (L-CLF) was studied in mice infected with Mycobacterium tuberculosis Erdman. Groups of mice were treated with either free clofazimine (F-CLF), L-CLF, or empty liposomes twice a week for five treatments beginning on day 1 (acute), day 21 (established), or day 90 (chronic) postinfection. One day after the last treatment, the numbers of CFU of M. tuberculosis in the spleen, liver, and lungs were determined. F-CLF at the maximum tolerated dose of 5 mg/kg of body weight was ineffective; however, 10-fold-higher doses of L-CLF demonstrated a dose response with significant CFU reduction in all tissues without any toxic effects. In acutely infected mice, 50 mg of L-CLF/kg reduced CFU 2 to 3 log units in all three organs. In established or chronic infection, treated mice showed no detectable CFU in the spleen or liver and 1- to 2-log-unit reduction in the lungs. A second series of L-CLF treatments cleared M. tuberculosis in all three tissues. L-CLF appears to be bactericidal in the liver and spleen, which remained negative for M. tuberculosis growth for 2 months. Thus, L-CLF could be useful in the treatment of tuberculosis.

In a bioassay guided search for antimycobacterial compounds from higher plants, the root extracts of Elecampane (Inula helenium L.; Asteraceae) and Sweet Coneflower (Rudbeckia subtomentosa Pursh.; Asteraceae) were chemically investigated for their active constituents. Chromatographic fractions of root extracts of l. helenium, which exhibited significant activity against Mycobacterium tuberculosis, provided the known eudesmanolides alantolactone, isoalantolactone, and 11 alpha H, 13-dihydroisoalantolactone. Peracid epoxidation of alantolactone and isoalantolactone provided 5 alpha-epoxyalantolactone and 4(15) alpha-epoxyisoalantolactone, respectively and oxidation of alantolactone with OsO4 gave 11,13-dihydroxyalantolactone. Active fractions from R subtomentosa contained the known alloalantolactone and 3-oxoalloalantolactone. The structures of the above compounds were established by spectroscopic methods including 1D and 2D NMR techniques as well as spectral comparison with previously reported data. The molecular structure of 5 alpha-epoxyalantolactone was determined by single crystal X-ray diffraction. Eleven natural and semisynthetic eudesmanolides were tested in a radiorespirometric bioassay for activity against M. tuberculosis. 5 alpha-Epoxyalantolactone and encelin from Montanoa speciosa showed minimum inhibitory concentrations (MICs) of 8 and 16 micrograms ml-1, respectively. Alantolactone, isoalantolactone and its 4 alpha, 15-epoxide, 1,2-dehydro-3-epi-isotelekin and alloalantolactone gave MICs of 32 micrograms ml-1. All other compounds showed MIC values of 128 micrograms ml-1 or higher.

The minimum inhibitory concentrations (MIC) against Mycobacterium tuberculosis and M. avium of parthenolide, costunolide, 1 (10)-epoxycostunolide and other germacranolide-type sesquiterpene lactones and derivatives were determined by use of a radiorespirometric bioassay. Structure-activity relationship studies with natural and semisynthetic sesquiterpene lactones suggested that the alpha-methylene-gamma-lactone moiety is an essential, but not sufficient, structural requirement for significant in vitro activity against M. tuberculosis and M. avium.

Two-hundred and thirty crude organic extracts from 118 plant species distributed among 10 families were evaluated for anti-mycobacterial activity. Activity was determined against Mycobacterium tuberculosis H(37)Rv and Mycobacterium avium using the BACTEC 460 radiorespirometric assay. At 100 μg/ml, twenty-four and ten of the extracts caused more than 95% inhibition of growth of M. tuberculosis and M. avium, respectively. The most active plant species (100% inhibition) were Borrichia frutescens, Solidago arguta, and Inula helenium against M. tuberculosis, Euthamia leptocephala against M. avium, and Erigeron strigosus and Magnolia acuminata against both mycobacteria., (Copyright © 1998 Gustav Fischer Verlag. Published by Elsevier GmbH.. All rights reserved.)

A colorimetric, microplate-based Alamar Blue assay (MABA) method was used to determine the MICs of isoniazid (INH), rifampin, streptomycin (SM), and ethambutol (EMB) for 34 Peruvian Mycobacterium tuberculosis isolates (including both pansensitive and multidrug-resistant strains) and the H37Rv strain by using bacterial suspensions prepared directly from solid media. Results for all isolates were available within 8 days. Discordant results were observed on initial tests for 3 of 16 INH-susceptible isolates, 5 of 31 EMB-susceptible isolates, and 2 of 4 SM-resistant isolates (by the BACTEC 460 system). The overall agreements between the MICs obtained by MABA and the results obtained with the BACTEC 460 system were 87.9% for initial results and 93.6% after retesting 12 of 17 samples with discrepant results. Interpretation of MABA endpoints improved with technical experience. The MABA is a simple, rapid, low-cost, appropriate technology which does not require expensive instrumentation and which makes use of a nontoxic, temperature-stable reagent.

The crude methanol extract of the Kenyan shrub Leucas volkensii Gürke (Labiatae) displayed in a radiorespirometric bioassay antimycobacterial activity against Mycobacterium tuberculosis. Bioassay-guided fractionation of the crude extract led to the identification of (E)-phytol as the principal active component with a minimum inhibitory concentration (MIC) of 2 micrograms/ml, a value also observed for (3R,S,7R,11R)-phytanol, (Z)-phytol, and a commercially available 2:1 mixture of (E)- and (Z)-phytol. The derivatives (E)-phytol acetate, a mixture of the (2S,3S)- and (2R,3R)-isomers of (E)-phytol epoxide and (3R,S,7R,11R)-phytanic acid displayed lower activities with MICs of 8, 16, and > 128 micrograms/ml, respectively. Geraniol and farnesol, displayed MICs of 64 and 8 micrograms/ml, respectively. The activities of (E)-phytol, (Z)-phytol and (3R,S,7R,11R)-phytanol were found to be in the same range as ethambutol, a clinically useful drug with an MIC in the range 0.95-3.8 micrograms/ml.

Twelve patients were treated with three dose levels of minocycline for 30 days, primarily to detect the dose-related effects on Mycobacterium leprae viability, followed by another 5 months of daily minocycline for overall efficacy and persistence of clinical and antibacterial effects. Subsequently, the patients were given standard WHO/MDT chemotherapy for multibacillary leprosy. Clinical improvement was recognizable during the first month, occurring much earlier among those on minocycline 200 mg daily than those who received minocycline 100 mg daily. A similar change also was observed in one patient 11 days after three daily doses of 100 mg of minocycline. At the end of 6 months, all patients were clinically improved with a slight reduction in the average bacterial index (BI) and logarithmic index of bacilli in biopsy (LIB). The effects of minocycline on viability by mouse foot pad inoculation and palmitic acid oxidation assays were noted beginning at 10 to 14 days of daily dosing and becoming more definite after 30 days of treatment. Both tests correlated fairly well. Doses of 200 mg daily did not appear to be more efficient than minocycline 100 daily. Phenolic glycolipid-I (PGL-I) antigen determinations done on some patients during the first month remained positive and did not correlate with changes in viability results. At the end of 6 months, after 5 months of 100 mg of minocycline monotherapy, no viable organisms could be demonstrated by mouse foot pad inoculation and palmitic acid oxidation assays; assays for PGL-I antigen were all negative.(ABSTRACT TRUNCATED AT 250 WORDS)

The comparative bactericidal activities of sparfloxacin and ofloxacin against Mycobacterium leprae in mice were determined using the proportional bactericidal test at doses of 12.5 mg/kg-100 mg/kg. Significant bactericidal activity was found at 12.5 mg/kg sparfloxacin and 25 mg/kg ofloxacin. Sparfloxacin was significantly more bactericidal than ofloxacin at all doses, and the results with 25 mg/kg sparfloxacin were nearly identical to those obtained with 100 mg/kg ofloxacin. These results, together with pharmacokinetic and toxicological data in mice and man, suggest that sparfloxacin may have a higher therapeutic index than ofloxacin in leprosy, and that the tentative standard dosage of 200 mg sparfloxacin daily should be appropriate for a clinical trial.

Eighteen herbs used in the treatment of infectious diseases in traditional Chinese medicine were evaluated for in vitro activity against ten microbial pathogens. Lyophilized teas were tested by the agar dilution technique at 100-1600 micrograms/ml. Eleven of the preparations were active against at least one microorganism and six of these were active against at least three of the test isolates. Huangqin (Scutellaria sp.) and Huanglian (Coptis sp.) were each active against five of the isolates. Huangqin inhibited Klebsiella pneumoniae and Proteus vulgaris at 200 micrograms/ml. Huangqin alone showed strong activity against Mycobacterium smegmatis (less than or equal to 100 micrograms/ml) and Candida albicans (200 micrograms/ml). The antimicrobial activity of various teas, prepared with equal weights of herbs, could be compared against a particular pathogen by considering both the percentage of water-soluble material in the herbs and the minimum inhibitory concentrations of the filtered, lyophilized decoctions.

The effects of 22 antimicrobial agents on the incorporation of [U14C] palmitic acid ([U14C] PA) into the unique phenolic glycolipid-I (PGL-I) antigen of Mycobacterium leprae were studied. Nude-mouse-propagated M. leprae were incubated in a modified Dubos medium in the presence of antimicrobial agents for 4 days. [U14C] PA was then added and incubation was continued for 8 days. The antileprosy agents dapsone, rifampin, and clofazimine (2 micrograms/ml each) caused a significant reduction in [U14C] PA incorporation into PGL-I. Among other agents, the most active were erythromycin, chloramphenicol, and cerulenin. Low concentrations of ethionamide, tetracycline, and minocycline stimulated label incorporation. This system may prove useful in the evaluation of antileprosy agents.