(−)-Epigallocatechin 3-gallate (EGCG) is a natural polyphenol from green tea with reported anticancer activity and capacity to inhibit the lipogenic enzyme fatty acid synthase (FASN), which is overexpressed in several human carcinomas. To improve the pharmacological profile of EGCG, we previously developed a family of EGCG derivatives and the lead compounds G28, G37 and G56 were characterized in HER2-positive breast cancer cells overexpressing FASN. Here, diesters G28, G37 and G56 and two G28 derivatives, monoesters M1 and M2, were synthesized and assessed in vitro for their cytotoxic, FASN inhibition and apoptotic activities in MDA-MB-231 triple-negative breast cancer (TNBC) cells. All compounds displayed moderate to high cytotoxicity and significantly blocked FASN activity, monoesters M1 and M2 being more potent inhibitors than diesters. Interestingly, G28, M1, and M2 also diminished FASN protein expression levels, but only monoesters M1 and M2 induced apoptosis. Our results indicate that FASN inhibition by such polyphenolic compounds could be a new strategy in TNBC treatment, and highlight the potential anticancer activities of monoesters. Thus, G28, G37, G56, and most importantly M1 and M2, are anticancer candidates (alone or in combination) to be further characterized in vitro and in vivo.

Recent strong restrictions on the use of pesticides has prompted the search for safer alternatives, being antimicrobial peptides promising candidates. Herein, with the aim of identifying new agents, 15 peptides reported as plant defense elicitors, promiscuous, multifunctional or antimicrobial were 20 selected and tested against six plant pathogenic bacteria of economic importance. Within this set, KSL-W (KKVVFWVKFK-NH 2 ) displayed high antibacterial activity against all the tested pathogens, low hemolysis and low phytotoxicity in tobacco leaves. This peptide was taken as a lead and 49 analogues were designed and synthesized, including N-terminal deletion sequences, peptides incorporating a Damino acid and lipopeptides. The screening of these sequences revealed that a nine amino acid length 25 was the minimum for activity. The presence of a D-amino acid significantly decreased the hemolysis and endowed KSL-W with the capacity to induce the expression of defense-related genes in tomato plants. The incorporation of an acyl chain led to sequences with high activity against Xanthomonas strains, low hemolysis and phytotoxicity. Therefore, this study demonstrates that KSL-W constitutes an excellent candidate as new agent to control plant diseases and can be considered as a lead to develop 30 derivatives with multifunctional properties, including antimicrobial and plant defense elicitation. Keywords35 D-Amino acids; Lipopeptides; Plant pathogens; Plant defense elicitors have identified linear undecapeptides, cyclic decapeptides and triazolyl or acylated derivatives with 55high antibacterial activity, low hemolysis and phytotoxicity, and reasonable susceptibility to protease degradation [19][20][21][22]. Moreover, we have recently investigated a new strategy for plant disease management based on the use of peptides as plant defense elicitors. Interestingly, we have found sequences from the aforementioned families that are able to induce defense responses on tobacco cells and tomato plants, and that efficiently control fire blight infections on pear [23]. 60 4 The finding of new antimicrobial peptides active in vivo against plant pathogens demands the accessibility to a wide range of sequences with high activity in vitro. Realizing this need, we selected sequences described in the literature as plant defense elicitors, promiscuous, multifunctional or antimicrobial to be further tested against our target plant pathogens.Among peptide elicitors, we chose PIP-1 (YGIHTH-NH 2 ), identified through combinatorial 65 chemistry, and Pep-13 (VWNQPVRGFKVYE-OH), a pathogen-associated molecular pattern (PAMP) from Phytophthora sojae, which trigger multiple defense responses in plant cells [24][25][26][27][28]. The promiscuous peptides studied were the AMPs Cn-AMP1 (SVAGRAQGM-NH 2 ), Cn-AMP2 (TESYFVFSVGM-NH 2 ) and Cn-AMP3 (YCSYTMEA-NH 2 ) identified from green coconut (Cocos nucifera) water [29,30]. 70Regarding multifunctional peptides, we considered QKALNEINQF-NH 2 (p10) and TKKTKLTEEEKNRL-NH 2 (p14) which were isolated from bovine...

In this paper, peptide conjugates were designed and synthesized by incorporating the antimicrobial undecapeptide BP16 at the C- or N-terminus of the plant defense elicitor peptide flg15, leading to BP358 and BP359, respectively. The evaluation of their in vitro activity against six plant pathogenic bacteria revealed that BP358 displayed MIC values between 1.6 and 12.5 μM, being more active than flg15, BP16, BP359, and an equimolar mixture of BP16 and flg15. Moreover, BP358 was neither hemolytic nor toxic to tobacco leaves. BP358 triggered the overexpression of 6 out of the 11 plant defense-related genes tested. Interestingly, BP358 inhibited Erwinia amylovora infections in pear plants, showing slightly higher efficacy than the mixture of BP16 and flg15, and both treatments were as effective as the antibiotic kasugamycin. Thus, the bifunctional peptide conjugate BP358 is a promising agent to control fire blight and possibly other plant bacterial diseases.

The first solid-phase strategy for the synthesis of cyclic depsipeptides containing a phenyl ester linkage in their structure is described. The key steps of the synthesis were the formation of the phenyl ester bond and the on-resin head-to-side-chain cyclization. The amino acid configuration significantly influenced the formation and the stability of the cyclic depsipeptides. The presence of a l-Tyr(1) and a d-Tyr(7) led to the most stable sequences.

A rapid and efficient solid-phase strategy for the synthesis of dehydroxy fengycins derivatives is described. This synthetic approach involved the linkage of a Tyr to a Wang resin via a Mitsunobu reaction and the elongation of the peptide sequence followed by subsequent acylation of the N-terminus of the resulting linear peptidyl resin, esterification of the phenol group of a Tyr with an Ile, and final macrolactamization. The amino acid composition as well as the presence of the N-terminal acyl group significantly influenced the stability of the macrolactone. Cyclic lipodepsipeptides with a L-Tyr 3 /D-Tyr 9 configuration were more stable than those containing the Tyr residues with an opposite configuration. This work constitutes the first approach on the total solid-phase synthesis of dehydroxy fengycin derivatives.

A library of 66 cyclic decapeptides incorporating a Trp residue was synthesized on solid phase and screened against the phytopathogenic bacteria Pseudomonas syringae pv. syringae, Xanthomonas axonopodis pv. vesicatoria, and Erwinia amylovora. The hemolytic activity of these peptides was also evaluated. The results obtained were compared with those of a collection of Phe analogues previously reported. The analysis of the data showed that the presence of the Trp improved the antibacterial activity against these three pathogens. In particular, 40 to 46 Trp analogues displayed lower minimum inhibitory concentration (MIC) values than their corresponding Phe counterparts. Interestingly, 26 Trp-containing sequences exhibited MIC of 0.8 to 3.1 μM against X. axonopodis pv. vesicatoria, 21 peptides MIC of 1.6 to 6.2 μM against P. syringae pv. syringae and six peptides MIC of 6.2 to 12.5 μM against E. amylovora. Regarding the hemolysis, in general, Trp derivatives displayed a percentage of hemolysis comparable to that of their Phe analogues. Notably, 49 Trp-containing cyclic peptides showed a hemolysis ≤ 20% at 125 μM. The peptides with the best biological activity profile were c(LKKKLWKKLQ) (BPC086W) and c(LKKKKWLLKQ) (BPC108W), which displayed MIC values ranging from 0.8 to 12.5 μM and a hemolysis ≤ 8% at 125 μM. Therefore, it is evident that these Trp sequences constitute promising candidates for the development of new agents for use in plant protection.

The solid‐phase synthesis of cyclic lipopeptidotriazoles derived from the cyclic decapeptide c(Lys‐Lys2‐Leu‐Lys‐Lys5‐Phe‐Lys‐Lys‐Leu‐Gln) (BPC194), incorporating a triazolyl ring at Lys2 and a hexanoyl group at Lys5, was studied. Four different strategies that required the use of five orthogonal protecting groups (Fmoc, tBu, All, pNZ, ivDde) were explored. The influence of the side‐chain protection of Lys2 and Lys5 with the ivDde and pNZ groups was evaluated by incorporating Lys2(ivDde)/Lys5(pNZ) or Lys2(pNZ)/Lys5(ivDde). The order of removal of these protecting groups and of the introduction of the hexanoyl and triazolyl moieties was also studied. The best strategy included: (i) synthesis of a cyclic peptidyl resin bearing Lys2(ivDde) and Lys5(pNZ); (ii) pNZ group removal; (iii) acylation with hexanoic acid; (iv) ivDde group removal; and (v) acylation with propiolic acid followed by an azide–alkyne 1,3‐dipolar cycloaddition. By using this protocol, a set of cyclic lipopeptidotriazoles was prepared in high purities.

The consequences of plant pathogens on crop production together with the lack of effective and environmentally friendly pesticides evidence the need of new agents to control plant diseases. Antimicrobial and plant defense elicitor peptides have emerged as good candidates to tackle this problem.