Triterpenoids from Lawsonia alba.

Two pentacyclic triterpenoids have been isolated from the aerial parts of Lawsonia alba. The structures of the new constituents, named as lawsonic acid and lawsonin have been elucidated as 3 alpha-E-ferulyloxy-lup-20(29)-en-28-oic acid and 3 alpha-E-ferulyloxy-urs-11-en-13 beta-ol respectively through spectroscopic studies.     

Crystal structure at 87 K of sodium α-l-guluronate dihydrate

X-Ray data collected at 87 K showed crystals of sodium α-l-guluronate dihydrate (C₆H₉O₇Na · 2 H₂O) to be orthorhombic, P2₁2₁2₁ with a = 7.591(2), b = 18.884(5), c = 6.842(2) Å, and Z = 4. The structure was solved by direct methods, and full-matrix least-squares refinement based on 1587 F_o yielded R = 0.043 and R_w = 0.033. The structure analysis indicates partial anomeric disorder with α:β ～90:10. The guluronate ring has the ¹C₄(l) conformation. Sodium binds two translation-equivalent guluronate units and one water molecule in a primary five-fold coordination. The complexing oxygen functions, which include all axial hydroxyl groups and one carboxylate oxygen atom in the guluronate ring, describe a distorted trigonal bipyramid. A prominent feature of the crystal structure is the stacks of sodium atoms and guluronate residues in alternating sequence along the c axis. The stacks are held together by an intricate system of hydrogen bonds involving all oxygen atoms in the structure. The water molecules play an important role in this system both as hydrogen donors and acceptors.     

Diurnal variations in a shallow tropical freshwater fish pond in Shahjahanpur,U.P. (India)

Summary Diurnal variations in water chemistry and plankton in this eutrophic tropical freshwater ponds were quite apparent. Large fluctuations were noted in dissolved oxygen, pH, carbonate and bicarbonate concentrations. The pond water gets oversaturated with oxygen during day (24.2 p.p.m.) and depleted in the night (1.2 p.p.m.). Diurnal migrations of plankton were not in conformity with temperate waters.     

Dehydrophenylalanine analogues: conformational characterization.

Few dehydrophenylalanine (deltaPhe) analogues (X-deltaPhe-Phe-Gly-X1, X = Ac-; Boc-; Z-; X1 = OMe; OH; ONH2) of virus replication inhibiting peptide (Z-D-Phe-Phe-Gly) were synthesized, and their solution conformations were investigated by 1H NMR, UV and circular dichroism (CD) spectroscopy. Homogeneity of these analogues was also assessed by reverse phase-high performance liquid chromatography (RP-HPLC) using water-acetonitrile gradients.