The uptake of amino acids by the cyanobacterium Planktothrix rubescens is stimulated by light at low irradiances

The rates of uptake of five amino acids--alanine, glutamate, glycine, leucine and serine--by axenic cultures of the cyanobacterium Planktothrix rubescens were measured over a range of irradiances using the (14)C-labelled amino acids at the nanomolar concentrations observed in Lake Zürich. The rates in the light exceeded the dark rates by as much as two- to ninefold. The light-affinity constants for stimulation were similar, indicating a similar process for each of the five amino acids. The E(k) (light saturation irradiance) for light stimulation was only 1 micromol m(-2) s(-1), less than the compensation point for photosynthesis and autotrophic growth, and much lower than the E(k) for either process. The E(k) for amino acid uptake was also less than the irradiance at which filaments obtain neutral buoyancy, which determines the depth at which they stratify and the irradiance they receive. This indicates that stimulation of amino acid uptake by light of low irradiances provides a mechanism for supplementing growth of filaments stratifying deep in the metalimnion, which, while able to grow at low irradiances, are often left with insufficient light to sustain them. Acetate uptake was also stimulated by light, but the kinetics differed.     

Three angiotensin-converting enzyme inhibitors from Rabdosia coetsa

The EtOAc extract of Rabdosia coetsa showed angiotensin-converting enzyme (ACE) inhibitory activity. Bioassay-guided isolation of this extract yielded ethyl caffeate (1), rosmarinic acid (2) and methyl rosmarinate (3), which inhibited ACE activity by 32.42%, 55.19% and 39.50% respectively, at the concentration of 10 μg/ml.     

Amino acid incorporation by a natural population of Oscillatoria rubescens. A microautoradiographic study

Abstract The incorporation of a very low concentration (0.015 μM) of an [³H]amino acid mixture was measured for a natural population of Oscillatoria rubescens DC in samples from a eutrophic lake, Lake Nantua (France).
The kinetics of amino acid incorporation in the size fraction ⩾12 μ m showed that uptake was fast and that the maximum was reached after 4 h.
Microautoradiography demonstrated that Oscillatoria rubescens is able to utilize for protein synthesis an external pool of amino acids whose [³H] label becomes distributed generally throughout the cell.     

Studies on Diterpenoids ot Rabdosia macrocalyx var. jiuhua Z. W. Xue et X. W. Wang

Four diterpenoids have been isolated from the dried leaves of Rabdosia macrocalyx var. juihua Z. W. Xue et X..W. Wang. Three of them were shown to be known diter- penoids, excisanin A, excisanin B and macrocalyxin A, while the one, a new kauranetype diterpene, was named jiuhuanin A. On the basis of physico-chemical constants, spectroscopic analysis of the new compound and properties of its derivatives, the structure of the compound was identified as (1). Jiuhuanin A was shown to have cytotoxicity in vitro against cultures of Hela cell and A549 cells.     

Chemical Structures of Reniformin A,B, and C

Three new cytotoxic diterpenoids reniformin A, B and C, have been isolated from the leaves of Rabdosia latifolia var. reniformis Z. W. Xue et X. W. Wang. Their structures were established as (1), (2), and (3) by spectroscopic and chemical data respectively.     

Studies on the Diterpenoids of Rabdosia ternifolia

From the whole plant of Rabdosia ternifolia (Labiatae) two diterpeno-ids were isolated. One of them is a new tetracyclic diterpenoids named ternifolin. Bymeans of spectral methods combined wish chemical conversion ternifolin is assigned as6-acetylsodoponin (Ⅲ). The other one is identified as sodoponin (Ⅰ).     

The Chemical Constituents of Rabdosia coetsa

From the leaves of Rabdosia coetsa (Buch.-Ham. ex D. Don) Ham, a new kauranoic acid, coetsanoic acid, along with eight known compounds, dihydrorabdoktmmin C, rabdoktmmin C, albopilosin A, maerocalyxin C, N-2'-hydroxy-eieosanoyl ( henicosanoyl-hexacosanoyl )-4-hydroxy- trans-8-sphingenine,ursolic acid, 2a, 3β-dihydroxyursolie acid and daucosterol has been isolated. Its structure was established as 7a, 12a, 14β-tri-hydroxy-15-oxo-ent-kauran-18-carboxy acid by spectroscopic means. The ceramides were isolated from the plants of Rabdosia for the first time.     

甘肃香茶菜属药用植物资源分布及其利用对策

目的：调查统计甘肃省香茶菜属药用植物资源,为该属植物资源的合理开发利用提供科学依据。方法：野外调查、采集标本和查阅相关文献资料。结果：经初步研究,甘肃省有12种该属植物,记述了它们在省内的主要分布范围及药用价值。结论：甘肃东南部香茶菜属植物资源较为丰富,有待进一步研究,并提出了相应的开发保护措施。