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Two new tirucallane-type triterpenoids, (24 Z)-tirucalla-7,24-diene-3 β,11 β,26-triol ( 1) and (3 S,24 R)-tirucall-7-ene-3,24,25-triol ( 2), along with the known compound celastrol ( 3), were isolated from the root barks of Celastrus stylosus Wall. The structures of 1- 3 were established by spectroscopic methods, including extensive 2D NMR and MS analyses. It is the first report on tirucallane-type triterpenoids from the genus Celastrus and may be of vital chemotaxonomic significance. [ABSTRACT FROM AUTHOR]

Two new C21 steroidal glycosides named as cynotophyllosides K-L, were isolated from the roots of Cynanchum otophyllum, together with three known steroids cynotophylloside H, sarcostin and deacetylmetaplexigenim. The structure of the new compounds were established by spectroscopic and chemical analyses, especially 2D NMR techniques. [ABSTRACT FROM AUTHOR]

Cleisostorna Bl. is an orchid genus with approximately 100 accepted species widely distributed in tropical and subtropical areas. There are about 16 species in China (4 endemic) before. Cleisostoina aspersuin (Rchb. f.) Garay, so far known only from Yunnan, is reported from China. A detailed description and photos are provided. This species is easily distinguished from its relatives by bilobulate leaves, fat and obtuse midlobe of the lip, conical rostellum with an oblique apex, and beaked operculum. It is similar to Cleisostoma discolor Lindl. in floral morphology, but the latter differs by having a lip with thin spathulate truncate midlobe, with erose front edge. [ABSTRACT FROM AUTHOR]

Abstract: The formation mechanism of pyrazine aroma compounds in the reaction between 1,4-13C-labeled l-ascorbic acid and l-glutamic acid was investigated. MS data indicated that the C-1 of l-ascorbic acid was not involved in the pyrazine formation. The α-amino carbonyl or α-amino hydroxy compounds were found to be the precursors of pyrazines. l-Glutamic acid could release ammonia when heated in aqueous solution. During the thermal degradation of l-ascorbic acid, some active intermediates such as acetol, hydroxybutadione and butanedione could be produced. These intermediates reacted with ammonia to generate α-amino carbonyl or α-amino hydroxy compounds, which then formed pyrazines. The odor quality of the pyrazine aroma compounds generated from l-ascorbic acid and l-glutamic acid was evaluated. The pyrazines may contribute to the toasted, roasted, nutty and burnt smells. [Copyright &y& Elsevier]