The plant substance, lapachol, which is a hydroxyquinone, an antitumor agent, and an uncoupling agent, mimics the behaviour of the classical uncoupling agent 2, 4-dinitrophenol in the following manner. Firstly, an ATP energized mitochondrial volume change is induced by the combination of lapachol with showdomycin (a nonmercurial thiol reagent which is an antibiotic and also an antitumor agent). Secondly, an appropriate concentration of lapachol is capable of inhibiting the ATP energized mitochondrial volume change induced by gramicidin in the presence of the permeant ions potassium and L-malate. The further addition of showdomycin reinstates an effect of gramicidin. Thus lapachol exposes a strategically located mitochondrial thiol group which occupies a pivotal position between a cycle which meshes with the respiratory chain and a cycle which meshes with ATP. This role for lapachol is in agreement with our previous hypothesis that the cycle meshing with the respiratory chain involves quinones, hydroxyquinones and hydroquinones and that lapachol acting as a foreign hydroxyquinone interferes with this cycle and exposes the mitochondrial thiol group normally meshing with the cycle. The hydroxyquinone lawsone also mimics 2, 4-dinitrophenol. Lawsone is decidedly less effective than lapachol. Lawsone unlike lapachol does not possess an isopentenyl side chain. A simple test has been devised for selecting combinations of antitumor agents which act against a single intracellular target, such as mitochondria.

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A new antibiotic, hondamycin, was isolated from the mycelium of Streptomyces griseochrontogenes var. albicus¹⁾, as colorless crystals. The antibiotic is active against phytopathogenic fungi and Trichophyton spp. Structural studies showed that the antibiotic has a molecular formula of C₄₇H₇₈O₁₃ and a molecular weight of about 850. This result was confirmed by high resolution mass spectrography of hondamycin triacetate.

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A strain, Streptomyces sp. No. 771, was isolated from a soil sample collected in Chiba Prefecture. The strain produced a new antibiotic which was isolated as colorless hexagonal crystals and named hondamycin. Hondamycin is mainly active against phytopathogenic fungi and Trichophyton, but is not active against any bacteria. The LD₅₀ was 1.43mg/kg by intraperitoneal route and greater than 500mg/kg orally. This strain was recognized to be a variety of Streptomyces griseochromogenes and named Streptomyces griseochromogenes var. albicus.

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The oxidation and alkaline degradation of the antibiotic hondamycin (C₄₇H₇₈O₁₃) give a tentative identification of the various functional groups.Evidence for an α, β-unsaturated ester group was obtained from ultraviolet, infrared and nuclear magnetic resonance spectra. Catalytic hydrogenation resulted in the reduction of four double bonds.

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The isolation, some chemical and biological properties of a new antitumour antibiotic Actinoxanthin are described. It was found to be a low-molecular weight protein.

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The biosynthesis of lucensomycin in cultures of Streptomyces lucensis has been studied using ¹⁴C-labelled precursors. The aglycone arises from two propionate and twelve acetate units. One propionate unit provides the chain-initiating unit, whilst the second, involved in chain-extension, undergoes oxidation of its methyl group to form the free carboxyl function of the aglycone.

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By means of a two-step chromatographic technique propionyl erythromycin. and erythromycin can be separated from the normal blood components and then from each other. The relative amounts of each form of the antibiotic can be determined on bioautograph plates by comparison of the zone sizes with those of a set of reference standards. Using this method, we have found that when propionyl erythromycin is added to blood there is an initial rapid hydrolysis to erythromycin. The hydrolytic rate decreases markedly with time, however, and overall is much slower than in buffer solution at the same pH. The rate of hydrolysis in blood differs with different animal species.

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Leupeptins, leupeptin Pr and leupeptin Ac, strongly inhibit proteolysis by plasmin, trypsin and papain, but do not inhibit proteolysis by α-chymotrypsin. The inhibition is competitive with substrates. The inhibitory effect on esterolysis by plasmin and trypsin is weaker than on proteolysis. The results with derivatives of leupeptins which contain carboxyl or alcohol instead of aldehyde and of di-n-butyl acetals of leupeptins indicate that the free aldehyde group plays a role in the activities. Leupeptins are absorbed orally and at least about 25 % is excreted in urine. Oral administration of leupeptins exhibited an anti-inflammatory effect on edema. Leupeptins inhibited thrombokinase reaction and coagulation of blood of human and rabbit. Type of inhibition was different from heparin. Coagulation of blood of rats and dogs are not inhibited. The effects of leupeptins on thrombokinase, thrombin, plasmin, trypsin, papain, kallikrein and α-chymotrypsin were compared with those of ε-aminocaproic acid, trans-4-aminomethylcyclohexanecarboxylic acid, soybean trypsin inhibitor and trasylol.

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Decrease of melting temperature (Tm) of Escherichia coli 15T^- DNA, with little breakage of the DNA strand, was observed in the presence of bleomycin A₂ and 2-mercaptoethanol. DNA digested more drastically with pancreatic deoxyribonuclease (E. C. 3.1.4.5) revealed no shift of Tm. When the DNA, treated with bleomycin and 2-mercaptoethanol, was dialyzed after heat denaturation, marked strand scission occurred. Tm of poly (dG)•poly (dC) decreased by 9°C with a change of transition width at 40μg/ml of bleomycin, although that of poly d(AT)•poly d(TA) showed no change. Single strand scission of synthetic deoxyribopolymers was observed to occur slightly in the presence of bleomycin and markedly when dialyzed after the incubation. Strand scission without dialysis was produced more significantly on poly (dG).poly (dC) than poly d(AT)•poly d(TA) in the presence of bleomycin.

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