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Effect of pretilachlor on nitrogen uptake and assimilation by the cyanobacterium Desmonostoc muscorum PUPCCC 405.10

100%

Singh D. P. , Khattar J. I. S. , Kaur G. , Gupta M. , Singht Y. , Gulati A.

nr 09

Tolerance limit, kinetics of nitrogen uptake and activity of nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS) enzymes of cyanobacterium Desmonostoc muscorum PUPCCC 405.10 were studied under the regime of chloroacetanilide herbicide pretilachlor. The organism was isolated from the paddy field under application of the herbicide and tolerated pretilachlor up to 10 ppm under laboratory conditions. The incubation of the cyanobacterium in 2.5 ppm pretilachlor did not cause significant effect on N uptake while supplementation of 5–10 ppm pretilachlor in medium reduced the rate of nitrate and nitrite uptake by 35–73 % with 50 % decrease in Vmax and no change in Km. These results indicated that herbicide did not affect the affinity of uptake system to nitrate and nitrite. In presence of herbicide, the activity of nitrogen assimilation enzymes was inhibited by 16 % for NR and 18 % for NiR. Unchanged Km and decreased Vmax (50–60 %) in presence of herbicide indicated non-competitive- type inhibition of the enzymes.A50 %decrease in Vmax and Km of ammonium uptake indicated un-competitive type inhibition of the ammonium transport system by the herbicide. GS activity also exhibited non-competitive inhibition in presence of pretilachlor with 21 % decrease in activity with unchanged Km and 40 % decrease in Vmax. Likewise, decreases in nitrogenase activity by 43 % and heterocyst formation by 40 % were recorded in presence of herbicide. Results indicated that pretilachlor affected nitrogen assimilation at uptake level and interacted with nitrogen-assimilating enzymes in a non-competitive manner.

Development and validation of an HPLC-UV-MS-MS method for identification and quantification of polyphenols in Artemisia pallens L.

100%

Niranjan A. , Barthwal J. , Lehri A. , Singh D. P. , Govindrajan R. , Rawat A. K. S. , Amla D. V.

tom Vol. 21, no. 1

105-116

Artemisia pallens L. (Compositae) is used in Indian traditional medicine to treat diabetes mellitus, jaundice, hysteria, body pain, and bacterial and fungal infections. A major cause of a variety of diseases is oxidative stress which is reduced by antioxidants such as polyphenols. These secondary metabolites are generally ubiquitous in plants and extensively used in the pharmaceutical, cosmetic, and food industries. In this study a simple and sensitive HPLC-UV-MS-MS-based method was developed for separation, identification, and quantification of polyphenols, for example gallic, protocatechuic, chlorogenic, caffeic, and ferulic acids, rutin, quercetin, and kaempferol. Amounts of polyphenols detected in 50% methanol-water extracts of the plant varied from 0.005% (kaempferol) to 0.24% (protocatechuic acid). Separation of the polyphenols was achieved on a reversed-phase C 18 with a mobile phase prepared from 1% aqueous with acetic acid and acetonitrile at a flow rate of 0.6 mL min -1 . The phenolic compounds were detected by UV absorption at 254 nm. The method was validated for linearity, accuracy, precision, LOD, LOQ, specificity, selectivity, and compound stability. Results from intra and inter-day validation (n = 6) showed the method was efficient and rapid. The optimized method was applied to extracts of A. pallens for identification and quantification of the polyphenols. The reference standards and their presence in A. pallens were confirmed by mass spectrometry.