Two new dihydrostemofoline alkaloids, 11(S),12(R)-dihydrostemofoline (3) and stemoburkilline (4), along with stemofoline (1) and 2'-hydroxystemofoline (2) have been isolated from a root extract of Stemona burkillii Prain. The structure and relative configuration of 3 have been determined via spectroscopic data and from comparison with synthetic 11(S),12(S)-dihydrostemofoline (5). The configuration of the exo-cyclic alkene group in 4 is tentively assigned as E on the basis of mechanistic considerations.
Two new tuberostemonine alkaloids, tuberostemonine L (3) and tuberostemonine M (4) and a new stemofoline alkaloid, (3'S)-hydroxystemofoline (5), along with two known alkaloids, (2'S)-hydroxystemofoline (1) and neotuberostemonine (2) have been isolated from a root extract of an unidentified Stemona species (Stemona sp.). The structure and relative configuration of these new alkaloids has been determined by spectral data interpretation, while the 3'S configuration of 5 was determined from NMR analysis of its (R)-and (S)-Mosher esters.
Polyglutamic acid ( -PGA) has been reported to be an effective biosorbent for metal ions. In vitro binding of lead (II) (Pb) by -PGA produced from Bacillus subtilis NBRC16449 was examined and the effect of Pb and -PGA on Brassica chinensis L. grown in the laboratory was investigated. The results revealed that the optimal pH for Pb adsorption was 5.0. -PGA was stable at 35-50°C and pH 5-7. The maximum removal efficiency was 87.9%. Brassica chinensis L. seeds were germinated and grown at 28±1 C on filter paper soaked with Pb solution at 0, 50, 100 and 250 M and -PGA at 0, 100, 500 and 1,000 mg/L for 7 days. The results indicated that Pb markedly inhibited growth of roots by reducing root length (P<0.05). However; the addition of 500 mg/L -PGA significantly protected seedlings from the adverse effects of Pb (P<0.05). Thus, -PGA has high potential as a biopolymer to be used for alleviation of Pb toxicities in plants.
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