NAC Transcription Factors Role in Various Biotic and Abiotic Stresses

NAC transcription factors are considered as main family of transcriptional regulators in plants. NAC gene family members play significant contribution in regulating transcriptional reprogramming in plants related to plant stress response. These proteins possess highly conserved DNA binding domains and play a diverse functions in several plants. NAC gene is related to several stress factors including biotic and abiotic factors. NAC transcription factors controls several interrelated processes and their protein products can function as negative or positive regulators in many cellular processes. These regulatory functions are also controlled by NAC proteins such as auto and cross regulation. These regulatory proteins are regarded as a central regulator for the interaction of phytohormones in various stress signaling pathways. This review highlights the role of NAC transcription factors in modulating gene expression and their role in various biotic and abiotic stress tolerance in plants.

Development and Evaluation of Sustained Release Antiepileptic Drug Using Natural Gums and Polymers

The present study was based on the development and evaluation of sustained release matrix tablets of antiepileptic drugs using natural gums and polymers. The carbamazepine and Phenytoin sodium were selected as model drugs and 48 formulations were prepared for each drug. The wet granulation and solvent evaporation methods were applied for the preparation of sustained release formulations of each drug. The guar gum, xanthan gum, HPMC, CMC and PVP-K90 were used alone and in combination in various drug to polymer ratio and the sustaining effect of these formulations were evaluated. After preparation, all the formulations were evaluated for various physical characteristics. The angle of repose, LBD, TBD, compressibility index, content uniformity of granules and hardness, thickness, friability, weight variation and drug content test were conducted for the evaluation of tablets. The drug release was studied using USP apparatus-I and various models like zero order, first order, Higuchi, Hixson- Crowell, and Korsmeyer were applied to the formulations in order to determine the drug release mechanism of these formulations. All the natural gums and polymers were subjected to prepare various formulations with drug to polymer ratio 1:1, 1:1.5, and 1:2. Formulations in which the natural gums (guar gum and xanthan gum) were used alone with drug to polymer ratio 1:1, 1:1.5, and 1:2. It was observed that both guar gum and Xanthan gum retards the drug release from the matrix tablets of both Carbamazepine and Phenytoin sodium up to 24 hours with drug to polymer ratio 1:2 formulation. Formulations containing HPMC alone as a sustaining agent retards the drug release for both the drugs up to 12 hours with drug to polymer ratio 1:2. CMC used in formulations alone as a retarding material, prolong the release of the drugs from the matrix tablets up to 8 hours with drug to polymer ratio 1:2. Similarly the polymers PVP-K90 were used alone in formulations where it sustained the drug release with drug to polymer ratio 1:2 up to 6 hours. It was also observed that when natural gums were incorporated with other polymers in formulations containing HPMC, CMC, and PVP-K90, enhance the sustaining effect as compared with the formulations prepared with polymers alone. It was observed that increasing polymers concentration decreased the release rate and enhanced sustaining effect. It was also seen that matrix tablets prepared by solvent evaporation method showed constant release, while those prepared by wet granulation method resulted fluctuation in release kinetics. Formulations prepared using natural gums with drug to gum ratios of 1:2 were subjected to in-vivo studies that showed promising results. Stability studies of successful formulations at normal and accelerated conditions were also carried out.