Biomedical subjects

I Kubo

Publications and source records attributed to I Kubo.

94 records · Page 6Linked to original sources

PubMedDate not supplied

Polygodial, an antifungal potentiator.

A series of sesquiterpene dialdehydes was isolated from the East African medicinal plants Warburgia stuhlmannii and Warburgia ugandensis (Canellaceae) as antibiotics, particularly against Saccharomyces cerevisiae, Candida utilis, and Sclerotinia libertiana. Among these sesquiterpene dialdehydes, polygodial [1] exhibited the most potent activity. When tested on S. cerevisiae, polygodial proved to be fungicidal rather than fungistatic. When the cells of S. cerevisiae are treated in vitro with polygodial for 10 min, the cell membrane becomes severely damaged, and many vesicles, possibly formed from the fragmented cell membrane, can be observed within the cytoplasm. The observation of cell membrane lesions led us to propose a rather innovative hypothesis: the use of polygodial to facilitate the transmembrane transport of exogenous chemicals into cells. For example, polygodial could be combined with an antibiotic having poor cell membrane permeability in an effort to increase its antibiotic activity by increasing its ability to gain entrance into the cell. We report here that a remarkably enhanced efficacy was obtained when actinomycin D was used in combination with polygodial. We believe polygodial may be acting as an "advance scout," punching holes in the plasma membrane and gaining an entrance into the cell for an antibiotic previously less effective because of problems with cell membrane permeability.

Antifungal Agents↗

PubMedDate not supplied

Isolation, structure, and synthesis of novel 4-quinolinone alkaloids from Esenbeckia leiocarpa.

Two new biocidal quinolinone alkaloids, 3-methoxy-1-methyl-2-propyl-4-quinolone [1] and 2(1'-ethylpropyl)-1-methyl-4-quinolone [2], were efficiently isolated using reversed-phase recycling hplc from the leaves of Esenbeckia leiocarpa. The structures were determined through spectroscopic data and confirmed by total synthesis. These alkaloids have antifeedant activities against the pink bollworm, Pectinophora gossypiella.

Alkaloids↗

PubMedDate not supplied

Sesquiterpenoids from Brachylaena hutchinsii.

The MeOH extract from the bark of Brachylaena hutchinsii yielded two ketoaldehyde sesquiterpenes, 8-ketocopaenal [1] and 8-ketoylangenal [2], which are also known as brachylaenalones A and B, respectively. In addition to the above-mentioned aldehydes, the corresponding ketoalcohols 8-ketocopaenol [3] and 8-ketoylangenol [4] were also isolated from the same plant, along with a fifth non-ketonic compound, ylangenol [5]. Although the ketoaldehydes 1 and 2 have already been described in the literature, their structures have not been completely established. We describe the isolation, identification, and antibacterial activity of five sesquiterpenes from Bra. hutchinsii and propose new structures for brachylaenalones A and B based on their spectral data.

Anti-Infective Agents↗

PubMedDate not supplied

Acetylcholinesterase and insect growth inhibitory activities of Gutierrezia microcephala on fall armyworm Spodoptera frugiperda J.E. Smith.

From the aerial parts of Gutierrezia microcephala (Asteraceae), four oxyflavones were isolated, namely 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone (1); 5,7,4'-trihydroxy-3,6,8-trimethoxyflavone (2); 5,7,2',4'-tetrahydroxy-3,6,8,5'-tetramethoxyflavone (3); 5,2'-dihydroxy-3,6,7,8,4',5'-hexamethoxyflavone (4), and an ent-clerodane, bacchabolivic acid (5). Compounds 1-5, the synthetic methyl ester (6), n-hexane and MeOH extracts were evaluated against the fall armyworm (Spodoptera frugiperda). Gedunin, a known insect growth regulator isolated from Cedrela spp. was used as a positive control. When tested for activity on neonate larvae into the no-choice artificial diet bioassay, flavone (1), clerodane (5), its methyl ester (6), MeOH and n-hexane extracts caused significant larval mortality with MC50 of 3.9, 10.7, 3.46, 7.95 and 7.5 ppm at 7 days, respectively, as well as growth reduction. They also increased the development time of surviving larvae and a significant delay in time to pupation and adult emergence. Acute toxicity against adults of S. frugiperda was also found, 5, 6, gedunin and n-hexane extract had the most potent activity with LD50 value of 6.59, 15.05, 10.78, and 12.79 ppm, respectively. In addition, MeOH, n-hexane extracts, 5, 6 and gedunin caused acetylcholinesterase inhibition with 93.7, 100, 90.2, 62.0 and 100% at 50.0 ppm, respectively; whereas 1-4 exhibited only moderate inhibitory activity. Compounds 1, 5 and 6 showed inhibitory activities comparable with gedunin. These compounds could be responsible of the insect growth inhibitory activity of this plant.

Acetylcholinesterase↗