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Cilembu sweet potato is one of Indonesia's leading agricultural commodities. The high carbohydrate content in sweet potatoes has the potential to change into sugar (glucose, sucrose, and fructose) during storage. The level of sweetness is one of the characteristics that determines the quality of sweet potatoes. The sweetness level of sweet potatoes is influenced by various factors, including genetics, environment, and their interactions. Apart from that, the role of invertase-producing bacteria in breaking down carbohydrates into sugars is very important. Information regarding the number of invertase-producing bacteria in Cilembu sweet potatoes and their activity during storage is still limited. This research aimed to determine the number and activity of invertase-producing bacteria in Cilembu sweet potatoes and estimate the relationship between activity and total invertase-producing bacteria during storage of Cilembu sweet potatoes. The results showed significant differences between the number and activity of invertase-producing bacteria at each storage time. There is a relationship between sugar levels and invertase-producing bacteria. Sucrose levels had a negative and significant correlation with fructose levels (-0.56) and invertase-producing bacteria (-0.58). Glucose levels were significantly and positively correlated with fructose levels (0.91) and invertase-producing bacteria (0.88). Fructose levels also significantly and positively correlated with invertase-producing bacteria (0.95). This information can be used as a reference in determining the quality of sweet potatoes directly and indirectly.

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Four new elaiophylin macrolides (1-4), together with five known elaiophylins (5-9), have been isolated from cultures of the Indonesian soil bacterium Streptomyces sp. ICBB 9297. The new compounds have macrocyclic skeletons distinct from those of the known dimeric elaiophylins in that one or both of the polyketide chains contain(s) an additional pendant methyl group. Further investigations revealed that 1 and 2 were derived from 3 and 4, respectively, during isolation processes. Compounds 1-3 showed comparable antibacterial activity to elaiophylin against Staphylococcus aureus. However, interestingly, only compounds 1 and 3, which contain a pendant methyl group at C-2, showed activity against Mycobacterium smegmatis, whereas compound 2, which has two pendant methyl groups at C-2 and C-2', and the known elaiophylin analogues (5-7), which lack pendant methyl groups at C-2 and/or C-2', showed no activity. The production of 3 and 4 in strain ICBB 9297 indicates that one of the acyltransferase (AT) domains in the elaiophylin polyketide synthases (PKSs) can recruit both malonyl-CoA and methylmalonyl-CoA as substrates. Bioinformatic analysis of the AT domains of the elaiophylin PKSs revealed that the ela_AT7 domain contains atypical active site amino acid residues, distinct from those conserved in malonyl-CoA- or methylmalonyl-CoA-specific ATs.

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Two new apoptolidins, 2'-O-succinyl-apoptolidin A (11) and 3'-O-succinyl-apoptolidin A (12), were isolated from the culture broth of an Indonesian Amycolatopsis sp. ICBB 8242. These compounds inhibit the proliferation and viability of human H292 and HeLa cells. However, in contrast to apoptolidin A (1), they do not inhibit cellular respiration in H292 cells. It is proposed that apoptolidins are produced and secreted in their succinylated forms and 1 is the hydrolysis product of 11 and 12.

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Apoptolidin A was first isolated as a secondary metabolite of a Nocardiopsis sp. and is the founding member of a family of potential selective cancer cell toxins. We now report the isolation, production and pharmacological characterization of apoptolidins A and C from an alternate actinomycete producer, an Amycolatopsis sp. from soil samples collected in Indonesia. We investigated the action of apoptolidins A and C in representative human glioblastoma cells, lung cancer cells and mouse embryonic fibroblasts (MEFs) to better understand the mechanism of action of the known apoptolidins. Shifts in cellular metabolism in intact cells and the status of the AMP-activated protein kinase (AMPK) stress pathway in response to apoptolidin A were entirely consistent with the actions of an ATP synthase inhibitor. We find the metabolic phenotype of the cell to be a critical determinant of apoptolidin sensitivity and the likely basis for cancer cell selectivity. The apoptolidins induce indirect activation of AMPK and trigger autophagy in sensitive cell types without significant inhibition of mTORC1. Human U87-MG glioblastoma cells and wild type MEFs showed increased phosphorylation of AMPK (Thr172), ACC (Ser79) and ULK1 (Ser555), whereas AMPKα-null MEFs and more glycolytic SF-295 glioblastoma cells lacked this response. Although both are reported to be selective inhibitors of mitochondrial ATP synthase, differences between apoptolidin- and oligomycin A-induced responses in cells indicate that the action of these macrolides is not identical.

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Fractionation of the extract from the Indonesian Streptomyces sp. ICBB8198 as directed by the antibacterial activity delivered the known phenazine antibiotics griseoluteic acid (1a) and griseolutein A (1b), as well as two new phenazine derivatives (2 and 3). In addition, the known compounds spirodionic acid, dihydrosarkomycins, and 6-ethyl-4-hydroxy-3,5-dimethyl-2H-pyran-2-one (4a), along with the new pyrone 3,6-diethyl-4-hydroxy-5-methyl-2H-pyran-2-one (4b), were isolated. We report here the isolation, structure elucidation, and antibiotic activity of the new metabolites as well as a hypothetical pathway for the formation of the new phenazine derivatives.

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In our screening of Indonesian microorganisms for novel bioactive natural products we have isolated seven new compounds, designated as limazepines A, B1 and B2 (isolated as an isomeric mixture), C, D, E, and F, from the culture broth of Micrococcus sp. strain ICBB 8177. In addition, the known natural products prothracarcin and 7-O-succinylmacrolactin A, as well as two previously reported synthetic compounds, 2-amino-3-hydroxy-4-methoxybenzoic acid methyl ester and 4-ethylpyrrole-2-carboxaldehyde, were obtained from the extract. Chemical structures were determined by spectroscopic methods and by comparison with the NMR data of structurally related compounds. The limazepines belong to the growing group of the pyrrolo[1,4]benzodiazepine antitumor antibiotics isolated from various soil bacteria. Limazepines B1/B2 mixture, C, and E were active against the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli. Limazepine D was also active against S. aureus, but was not active against E. coli. Interestingly, only the limazepines B1/B2 mixture and D were active against Pseudomonas aeruginosa.

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Two Indonesian Streptomyces strains, ICBB8309 and ICBB8415, were investigated for their ability to produce antibiotic compounds. In addition to the known antibiotics actiphenol, naramycin B, and sabaramycin, six new angucyclinones were identified. The isolation, structure elucidation and biological activities for the six new compounds are presented. The angucyclinones 7-deoxo-6-deoxy-7-hydroxy-8-O-methylrabelomycin, 1-deoxo-1-hydroxy-8-O-methylrabelomycin, and the angucycline 7-deoxo-7-hydroxy-1-O-alpha-rhamnosyl-8-O-methyltetrangulol have common angular backbones, while angucyclinone C, limamycin A, and limamycin B appear to be rearranged angucyclinones.

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Six new angucyclinone polyketides named panglimycins A-F were isolated together with the three known metabolites (+)-fujianmycin A, (+)-ochromycinone, and emycin C from the bioassay-guided fractionation of the extract of the Indonesian Streptomyces strain ICBB8230. The new compounds are highly oxygenated angucyclinones that appear to be biosynthetically derived from ochromycinone or fujianmycin. Their structures were determined by X-ray crystal analysis, interpretation of 1D- and 2D-NMR spectra, and comparison of the data with those of structurally related known natural products. Despite structural similarities to angucyclinones with antibiotic activities, the panglimycins did not exhibit any growth inhibition when tested against several bacteria and fungi.

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Modern sugarcane cultivars have complex genetic characteristics and low fertility that render their genetic improvement through traditional breeding difficult. Genetic engineering methodology to introduce foreign genes provides new opportunities for the genetic improvement of sugarcane cultivars. One of prerequisites for successful insertion of a gene cassette into the plant genome is the availability of an efficient transformation protocol. An improved protocol for Agrobacterium-mediated transformation of sugarcane is described. Between 85 and 100% of calli transformed using this procedure produced new calli, and 100% of them were positive for the inserted gene. The whole procedure permitted the production of transgenic calli in a short time (1.5 mo). The transformed calli can be cultured further for the production of the inserted gene-encoded enzyme by using cell culture, or they can be regenerated into transgenic plants. This protocol may be implemented also for the generation of transgenic plants from other species.

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