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Optimized nitrate reductase assay predicts the rate of nitrate utilization in the halotolerant microalga Dunaliella viridis (1997)

Javier, F. ; Gordillo, L. ; Jiménez, Carlos ; [et al.]

Springer

Journal of applied phycology 9 (1997), S. 99-106

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ISSN: 1573-5176

Keywords: Nitrate reductase ; in situ enzymatic activity ; Dunaliella viridis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract An in situ method for measuring nitrate reductase (NR) activity in Dunaliella viridis was optimized in terms of incubation time, concentration of KNO3, permeabilisers (1-propanol and toluene), pH, salinity, and reducing power (glucose and NADH). NR activity was measured by following nitrite production and was best assayed with 50 mM KNO3, 1.2 mM NADH, 5% 1-propanol (v/v), at pH 8.5. The estimated half-saturation constant (Ks) for KNO3 was 5 mM. Glucose had no effect as external reducing power source, and NADH concentrations 〉1.2 mM inhibited NR activity. Nitrite production was linear up to 20 min; longer incubation did not lead to higher nitrate reduction. The use of the optimized assay predicted the rate of NO 3 − removal from the external medium by D. viridis with high degree of precision.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007978512458

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Cytotoxic Triterpene Glycosides from Far-Eastern Sea Cucumbers Belonging to the Genus Cucumaria (1997)

Drozdova, Olga A. ; Avilov, Sergey A. ; Kalinin, Vladimir I. ; [et al.]

Weinheim : Wiley-Blackwell

Liebigs Annalen 1997 (1997), S. 2351-2356

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ISSN: 0947-3440

Keywords: Carbohydrates ; Cucumaria japonica ; Cucumaria miniata ; Sea cucumbers ; Cucumariosides ; Triterpene glycosides ; Antitumor activity ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: New cytotoxic triterpene oligoglycoside disulfates, cucumariosides A3 (1) and A6-2 (2), have been isolated from the sea cucumber Cucumaria japonica. The trisulfated cucumarioside A7-3 (4) was found to be the major component in the glycoside fraction of Cucumaria miniata. The structures were assigned on the basis of extensive spectral data (NMR and MS), selective solvolysis of desulfated derivative 3 and other chemical evidence. The presence or absence of a carbonyl group at C-16 of the aglycone and of sulfate groups at C-6 of the glucose and 3-O-methylglucose units are interpreted in terms of the functional evolution of sea cucumbers in order to improve their defensive system. Both (1) and (2) are cytotoxic in vitro at IC50 = 1 μg/ml against a selection of five human and mice tumoral cell lines.

Additional Material: 2 Ill.