Effect of replacing maize silage with red clover silage in the diet on milk fatty acid composition in cows.

This study aimed to evaluate the effect of replacing maize silage plus soybean meal with red clover silage (RCS) plus wheat on the fatty acid (FA) profile in the milk fat of cows. Forty-four lactating German Holstein cows were used in a 4 × 4 Latin square design with 21-d periods composed of 13 d of adaptation to diets followed by an 8-d sampling phase. Experimental diets offered as total mixed ration consisted of a constant forage-to-concentrate ratio (75:25) with target proportions of RCS to maize silage of 15:60 (RCS15), 30:45 (RCS30), 45:30 (RCS45), and 60:15 (RCS60) on a dry matter basis. Increasing the level of RCS in the diet was accompanied by a reduction of linoleic acid content in the diet and decreased linearly the proportions of linoleic acid in the milk up to 4%. Proportions of α-linolenic acid in milk increased 2-fold with RCS60 compared with RCS15, which resulted from the linear increase in α-linolenic acid intake with incremental levels of RCS. Vaccenic acid in the milk fat was reduced by 24%. Rumenic acid, a conjugated linoleic acid (cis-9,trans-11 conjugated linoleic acid) considered to be a human health promoter, was also decreased by 22%. Reduced rumenic acid in the milk fat was probably due to a reduced amount of vaccenic acid produced in the rumen and, consequently, to the low amount of vaccenic acid to be desaturated to rumenic acid in the mammary gland by Δ9-desaturase. Oleic acid was enriched in the milk fat, although the dietary concentration of oleic acid decreased. Stearic acid proportions remained constant with increasing levels of RCS. The proportions of total polyunsaturated FA were increased by 12%, and the long-chain FA proportions increased linearly with increasing levels of RCS. Myristic acid was reduced linearly, but palmitic acid remained constant. Saturated FA was reduced linearly by 2%. Branched-chain FA, which are presumed to possess anticarcinogenic properties, were reduced to a small extent only (quadratic effect). We conclude that replacing maize silage with RCS appears to alter milk FA composition by reducing linoleic acid intake and ruminal biohydrogenation. Feeding RCS represents a strategy to increase intake of α-linolenic acid in dairy cows. However, because changes in the FA profile show positive as well as negative effects, no distinct conclusions can be drawn with regard to human health benefits.

Michael acceptor based antiplasmodial and antitrypanosomal cysteine protease inhibitors with unusual amino acids.

New peptidic Michael acceptor based cysteine protease inhibitors displaying antiparasitic activity were identified by testing a broad series of 45 compounds in total, containing Asn, Gln, or Phe. As target enzymes, falcipain-2 and -3 from P. falciparum and rhodesain from T. b. rhodesiense were used. In the case of the Asn/Gln containing compounds, the trityl-protected, diastereomeric E-configured vinylogous dipeptide esters 16 (Boc-(S)-Phg-(R/S)-vGln(Trt)-OEt) were discovered as most active inhibitors concerning both protease inhibition and antiparasitic acitivity, with inhibition constants in the submicromolar range. The compounds were shown to display time-dependent and competitive inhibition. In the case of the Phe containing compounds, the maleic acid derivatives 42 and 43 (BnO-Phe<--Mal-Phe-OBn, BnO-Phe<--Mal-Phe-Ala-OBn, Mal = maleic acid) displayed good inhibition of rhodesain as well as good antitrypanosomal activity, while the fumaric acid derived E-analogue 14 (BnO-Phe<--Fum-Phe-OBn) only displayed inhibition of the target enzymes but no antiparasitic activity. Inhibition by these Phe derivatives was shown to be time-independent and competitive.

Synthesis and evaluation of non-peptidic cysteine protease inhibitors of P. falciparum derived from etacrynic acid.

A series of etacrynic acid derivatives was synthesized and screened for their in vitro activity against Plasmodium falciparum, as well as their activity against recombinantly expressed falcipain-2 and -3. The two most active compounds of the series displayed IC(50) values of 9.0 and 18.8 microM against Plasmodia.

Aziridide-based inhibitors of cathepsin L: synthesis, inhibition activity, and docking studies.

A comprehensive screening of N-acylated aziridine (aziridide) based cysteine protease inhibitors containing either Boc-Leu-Caa (Caa=cyclic amino acid), Boc-Gly-Caa, or Boc-Phe-Ala attached to the aziridine nitrogen atom revealed Boc-(S)-Leu-(S)-Azy-(S,S)-Azi(OBn)(2) (18 a) as a highly potent cathepsin L (CL) inhibitor (K(i)=13 nM) (Azy=aziridine-2-carboxylate, Azi=aziridine-2,3-dicarboxylate). Docking studies, which also accounted for the unusual bonding situations (the flexibility and hybridization of the aziridides) predict that the inhibitor adopts a Y shape and spans across the entire active site cleft, binding into both the nonprimed and primed sites of CL.

Screening of electrophilic compounds yields an aziridinyl peptide as new active-site directed SARS-CoV main protease inhibitor.

The coronavirus main protease, M(pro), is considered a major target for drugs suitable to combat coronavirus infections including the severe acute respiratory syndrome (SARS). In this study, comprehensive HPLC- and FRET-substrate-based screenings of various electrophilic compounds were performed to identify potential M(pro) inhibitors. The data revealed that the coronaviral main protease is inhibited by aziridine- and oxirane-2-carboxylates. Among the trans-configured aziridine-2,3-dicarboxylates the Gly-Gly-containing peptide 2c was found to be the most potent inhibitor.