First report on the synthesis and structural studies of trans-Phakellistatin 18: a rotamer of marine natural product phakellistatin 18.

Phakellistatin peptides from marine organisms are the sources of proline-rich cyclic peptides with reported significant antitumor activities. Phakellistatin 18 (1), reported from marine sponge Phakellia fusca, contains three proline-peptide linkages in cis form. We attempted the total synthesis of natural product 1 through solution-phase macrocyclization approach, as a result, the synthetic cyclic peptide 2 was obtained as a rotamer of natural product having all three proline residues in trans-conformation. Here, we describe the synthesis, structural, and cytotoxicity studies of trans-Phakellistatin 18 (2), and its analog [Ala1,3,6]-Phakellistatin 18 (3). Detailed NMR studies were carried out to characterize the synthesized peptides, and anti-cancer screening was performed by using MTT assay. The synthetic trans-Phakellistatin 18 (2) (IC50=67.5 ± 2.938 µM) showed comparable cytotoxicity against HepG2 cancer cell line with standard drug doxorubicin (IC50=63.88 ± 6.48 µM). Here, the first synthetic and structural studies on trans-Phakellistatin 18 (2), and its anticancer screening against HepG2 cell line was reported.

Phytochemical analysis and fertility enhancement effects of aerial parts of Fagonia arabica in male and female rats.

In this study, fertility enhancing effect of ethanol extract of aerial parts of Fagonia arabica was evaluated. 24 female and 12 male virgin Wistar rats (Average wt 150-250g) were selected. Dose was given daily for 23 days in 4 groups of animal. After 23 days, they were cohabitated for mating. Then dosing was continued for further 5 days. On 5th day of mating, sperm counting was done by observing vaginal smear under the microscope which showed fertility enhancement in male. Female were kept separately until delivery. The number of pubs born provided female fertility enhancement as compared to control. Average sperm count in 1 cm2 were counted in group A, B, C and control as 14.000±1.732, 12.000±1.000, 23.333±1.528 and 11.000±1.000 respectively. Number of pubs were counted in Group A, B, C and D as 8.667±2.082, 7.333±1.528, 7.333±1.528 10.000±2.000 and 5.333±0.577 respectively and fertility index was calculated for Group A, B and C as 62.516%, 37.502% and 87.512% respectively. Result showed that the orally administered dose of Fagonia arabica possess highly significant fertility enhancing activity in male and female rats after observing improvement in the sperm count and number of pubs as compared to control.

Phytohormones Trigger Drought Tolerance in Crop Plants: Outlook and Future Perspectives.

In the past and present, human activities have been involved in triggering global warming, causing drought stresses that affect animals and plants. Plants are more defenseless against drought stress; and therefore, plant development and productive output are decreased. To decrease the effect of drought stress on plants, it is crucial to establish a plant feedback mechanism of resistance to drought. The drought reflex mechanisms include the physical stature physiology and biochemical, cellular, and molecular-based processes. Briefly, improving the root system, leaf structure, osmotic-balance, comparative water contents and stomatal adjustment are considered as most prominent features against drought resistance in crop plants. In addition, the signal transduction pathway and reactive clearance of oxygen are crucial mechanisms for coping with drought stress via calcium and phytohormones such as abscisic acid, salicylic acid, jasmonic acid, auxin, gibberellin, ethylene, brassinosteroids and peptide molecules. Furthermore, microorganisms, such as fungal and bacterial organisms, play a vital role in increasing resistance against drought stress in plants. The number of characteristic loci, transgenic methods and the application of exogenous substances [nitric oxide, (C28H48O6) 24-epibrassinolide, proline, and glycine betaine] are also equally important for enhancing the drought resistance of plants. In a nutshell, the current review will mainly focus on the role of phytohormones and related mechanisms involved in drought tolerance in various crop plants.