Structure determination of two new sesquiterpenoids from Streptomyces sanglieri
Sesquiterpenoids are a group of abundant and structurally diverse secondary metabolites mainly derived from plant and fungi. By contrast, they are rarely isolated from bacteria, and the terpene synthase genes had been considered to be silent in prokaryotes. Recently, more and more terpenes were identified from bacteria, and the biosynthesis of some terpenes has been discussed in heterologous bacteria. Actually, it demonstrated that the terpene synthases are widely distributed in bacteria, including streptomycete, and some new sesquiterpenoids and diterpenoids had been obtained through heterologous expression of terpene synthase genes derived from Streptomyces microorganism. In our ongoing investigation of new bioactive natural products from streptomycete, two new sesquiterpenes, 15-hydroxy-(+)-epicubenol (1) and 7β-hydroxy-7-epi-α-eudesmol (2), were identified from a fermentation broth of Streptomyces sanglieri (YIM 121209-2), which was isolated from the forest soil sample collected from Wuyi Mountain, Fujian Province, China. The structures of compounds 1 and 2 (Fig. 1) were elucidated based on detailed spectroscopic data analyses, including 1D and 2D NMR techniques. The cytotoxicity against two human cancer cell lines and antimicrobial activity against a panel of bacteria and fungi of 1 and 2 were evaluated. None of them showed cytotoxic or antimicrobial activities at 100μg/ml.
Bafilomycins and Odoriferous Sesquiterpenoids from Streptomyces albolongus Isolated from Elephas maximus Feces.
From a fermentation broth of Streptomyces albolongus obtained from Elephas maximus feces, nine bafilomycins (1-9) and seven odoriferous sesquiterpenoids (10-16) were isolated. The structures of the new compounds, including three bafilomycins, 19-methoxybafilomycin C1 amide (1), 21-deoxybafilomycin A1 (2), and 21-deoxybafilomycin A2 (3), and two sesquiterpenoid degradation products, (1β,4β,4aβ,8aα)-4,8a-dimethyloctahydronaphthalene-1,4a(2H)-diol (10) and (1β,4β,4aβ,7α,8aα)-4,8a-dimethyloctahydronaphthalene-1,4a,7(2H)-triol (11), were elucidated by comprehensive spectroscopic data analysis. The cytotoxicity activity against four human cancer cell lines and antimicrobial activities against a panel of bacteria and fungi of all compounds isolated were evaluated. Compounds 1, 7, and 8 were cytotoxic, with IC50 values ranging from 0.54 to 5.02 μM. Compounds 2, 7, 8, and 10 showed strong antifungal activity against Candida parapsilosis, with MIC values of 3.13, 1.56, 1.56, and 3.13 μg/mL respectively.
THE PERFORMANCE OF STEADY DETONATION ENGINES
Propulsion systems driven by steady normal detonations are studied. The practical di‐culties associated with stabilizing a detonation wave are highlighted. The requirement on the freestream total enthalpy is considered in parallel with efiects such as condensation or auto-ignition of the fuel-air mixture and limitations associated with fuel sensitivity to detonation. A criterion for detonation stabilization is formulated and applied to an analytical treatment of a detonation ramjet and a detonation turbojet, which are the respective analogs of the ramjet and the turbojet using detonative combustion. The performance of these engines is evaluated and compared to the ideal ramjet and turbojet models for hydrogen and JP10. A limitation is placed on the maximum total temperature allowed in the combustor, based on material considerations. The results show that steady detonation engines have a small thrust-producing range, due to the requirements for detonation stabilization. Their performance is always lower than that of the conventional ramjet and turbojet because of the total pressure loss across the detonation.