Mycolic acid-containing bacteria (MACB) are known to activate cryptic natural product biosynthesis in co-cultures with actinobacteria. We cultured Actinosynnema mirum NBRC 14064, a producer of the mono-cyclic polyene macrolactam mirilactam A (6), with the MACB Tsukamurella pulmonis TP-B0596. As a result, three novel compounds (mirilactams C–E, 1–3) were produced in the co-culture conditions. Compounds 1–3 were likely derived from 6 by epoxidation and subsequent spontaneous cyclization. The chemical structures and stereochemistries of 1–3 were determined by spectroscopic analyses (NMR and MS), conformational searches in the optimized potentials for liquid simulations-3 (OPLS3) force field, and calculations of electronic circular dichroism (ECD).

Genus Dendrobium (Orchidaceae) contains numerous species. Phylogenetic analyses based on morphological characteristics and DNA sequences indicated that this genus is divided into two major groups: Asian and Australasian clades. On the other hand, little is known about the phytochemical differences and similarities among the species in each clade. In this study, we selected 18 Dendrobium species (11 from the Asian clade and 7 from the Australasian clade) and constructed HPLC profiles, arrays composed of relative intensity of the chromatographic peaks. Next, orthogonal partial least square discriminant analysis (OPLS-DA) was applied to the profile matrix to classify Dendrobium species into the Asian and Australasian clades in order to identify the peaks that significantly contribute to the class separation. In the end, two phenanthrenes, 4,9-dimethoxyphenanthrene-2,5-diol 1 and 1,5-dimethoxyphenanthrene-2,7-diol 2, which contributed to the class separation, were isolated from the HPLC peaks. The existence of 2 was limited to the genetically related Australasian species.

The isolation of useful microbes is one of the traditional approaches for the lead generation in drug discovery. As an effective technique for microbe isolation, we recently developed a multidimensional diffusion-based gradient culture system of microbes. In order to enhance the utility of the system, it is favorable to have diffusion coefficients of nutrients such as sugars in the culture medium beforehand. We have, therefore, built a simple and convenient experimental system that uses agar-gel to observe diffusion. Next, we performed computer simulations—based on random-walk concepts—of the experimental diffusion system and derived correlation formulas that relate observable diffusion data to diffusion coefficients. Finally, we applied these correlation formulas to our experimentally-determined diffusion data to estimate the diffusion coefficients of sugars. Our values for these coefficients agree reasonably well with values published in the literature. The effectiveness of our simple technique, which has elucidated the diffusion coefficients of some molecules which are rarely reported (e.g., galactose, trehalose, and glycerol) is demonstrated by the strong correspondence between the literature values and those obtained in our experiments.

The antiparallel triplex DNA is formed by the interaction between purine-rich triplex forming oligonucleotides (TFOs) and the homo-purine region within a duplex DNA. The formation of such a structure with the genome DNA promises to control the gene expression in a living cell. In this study, in an attempt to enhance the stability of the triplex DNAs, we have designed the N²-arylated deoxyguanosine derivatives. Among these analogues, we found that the TFOs containing N²-phenyl-2′-deoxyguanosine (PhdG) showed a stable and selective triplex DNA formation with the GC base pair as compared to the natural dG/GC triplet. However, the multiple incorporation of PhdG into the TFOs hampered the stable triplex DNA, instead, showed a tendency to form a higher order structure. Therefore, we concluded that the stable and selective triplex DNA formation is expected by the replacement of dG by PhdG in the purine-rich TFO sequence.

Dolastatin 16 is a cyclic depsipeptide isolated from the marine invertebrates and cyanobacterium Lyngbya majuscula, however, its bioactivity has been a historical question. In this study, peptidyl–prolyl cis–trans isomerase FKBP1A (FKBP12) was predicted as a potential target of dolastatin 16 via PharmMapper as well as verified using chemical–protein interactome (CPI) and molecular docking. FKBP1A has been previously identified as a target for the natural polyketide FK506 (tacrolimus), an immune suppressor inhibiting the rejection of organ transplantation in clinical use. The comparison study via the reverse pharmacophore screening and molecular docking of dolastatin 16 and FK506 indicated the good consistency of analysis with the computational approach. As the results, the lowest binding energy of dolastatin 16–FKBP1A complex was −7.4 kcal/mol and FK506–FKBP1A complex was −8.7 kcal/mol. The ligand dolastatin 16 formed three hydrogen bonds vs. four of FK506, as well as seven hydrophobic interactions vs. six of FK506 within the active site residues. These functional residues are highly repetitive and consistent with previously reported active site of model of FK506–FKBP1A complex, and the pharmacophore model was shown feasibly matching with the molecular feature of dolastatin 16.