Discovery of Natural Sesquiterpene Lactone 1-O-Acetylbritannilactone Analogues Bearing Oxadiazole, Triazole, or Imidazole Scaffolds for the Development of New Fungicidal Candidates

In recent decades, natural products have been considered important resources for developing of new agrochemicals because of their novel architectures and multibioactivities. Consequently, herein, 1-O-acetylbritannilactone (ABL), a natural sesquiterpene lactone from Inula britannica L., was used as a lead for further modification to discover fungicidal candidates. Six series of ABL-based derivatives containing an oxadiazole, triazole, or imidazole moiety were designed and synthesized, and their antifungal activities were also evaluated in vitro and in vivo. Bioassay results revealed that compounds 8d, 8h, and 8j (EC₅₀ = 61.4, 30.9, and 12.4 μg/mL, respectively) exhibited more pronounced inhibitory activity against Fusarium oxysporum than their precursor ABL (EC₅₀ > 500 μg/mL) and positive control hymexazol (EC₅₀ = 77.2 μg/mL). Derivatives 8d and 11j (EC₅₀ = 19.6 and 41.5 μg/mL, respectively) exhibited more potent antifungal activity toward Cytospora mandshurica than ABL (EC₅₀ = 68.3 μg/mL). Compound 10 exhibited excellent and broad-spectrum antifungal activity against seven phytopathogenic fungal mycelia. Particularly, the inhibitory activity of compound 10 against the mycelium of Botrytis cinerea was more than 10.8- and 2.3-fold those of ABL and hymexazol, respectively. Meanwhile, derivative 10 (IC₅₀ = 47.7 μg/mL) displayed more pronounced inhibitory activity against the spore of B. cinerea than ABL (IC₅₀ > 500 μg/mL) and difenoconazole (IC₅₀ = 80.8 μg/mL). Additionally, the in vivo control efficacy of compound 10 against B. cinerea was further studied using infected tomatoes (protective effect = 58.4%; therapeutic effect = 48.7%). The preliminary structure-activity relationship analysis suggested that the introduction of the 1,3,4-oxadiazole moiety (especially the 1,3,4-oxadiazole heterocycle containing the 4-chlorophenyl, 2-furyl, or 2-pyridinyl group) on the skeleton of ABL was more likely to produce potential antifungal compounds. These findings pave the way for further design and development of ABL-based derivatives as potential antifungal agents.

In vitro and in vivo evaluation of cnicin from blessed thistle (Centaurea benedicta) and its inclusion complexes with cyclodextrins against Schistosoma mansoni

Schistosomiasis, caused by a blood fluke of the genus Schistosoma, afflicts over 230 million people worldwide. Treatment of the disease relies on just one drug, praziquantel. Cnicin (Cn) is the sesquiterpene lactone found in blessed thistle (Centaurea benedicta) that showed antiparasitic activities but has not been evaluated against Schistosoma. However, cnicin has poor water solubility, which may limit its antiparasitic activities. To overcome these restrictions, inclusion complexes with cyclodextrins may be used. In this work, we evaluated the in vitro and in vivo antischistosomal activities of cnicin and its complexes with β-cyclodextrin (βCD) and 2-hydroxypropyl-β-cyclodextrin (HPβCD) against Schistosoma mansoni. Cnicin were isolated from C. benedicta by chromatographic fractionation. Complexes formed by cnicin and βCD (Cn/βCD), as well as by cnicin and HPβCD (Cn/HPβCD), were prepared by coprecipitation and characterized. In vitro schistosomicidal assays were used to evaluate the effects of cnicin and its complexes on adult schistosomes, while the in vivo antischistosomal assays were evaluated by oral and intraperitoneal routes. Results showed that cnicin caused mortality and tegumental alterations in adult schistosomes in vitro, also showing in vivo efficacy after intraperitoneal administration. The oral treatment with cnicin or Cn/βCD showed no significant worm reductions in a mouse model of schistosomiasis. In contrast, Cn/HPβCD complex, when orally or intraperitoneally administered to S. mansoni-infected mice, decreased the total worm load, and markedly reduced the number of eggs, showing high in vivo antischistosomal effectiveness. Permeability studies, using Nile red, indicated that HPβCD complex may reach the tegument of adult schistosomes in vivo. These results demonstrated the antischistosomal potential of cnicin in preparations with HPβCD.

New perspectives of purple starthistle (Centaurea calcitrapa) leaf extracts: phytochemical analysis, cytotoxicity and antimicrobial activity

Ethnobotanical and ethnopharmacological studies of many Centaurea species indicated their potential in folk medicine so far. However, investigations of different Centaurea calcitrapa L. extracts in terms of cytotoxicity and antimicrobial activity against phytopathogens are generally scarce. The phenolic profile and broad antimicrobial activity (especially towards bacterial phytopathogens) of methanol (MeOH), 70% ethanol (EtOH), ethyl-acetate (EtOAc), 50% acetone (Me₂CO) and dichloromethane: methanol (DCM: MeOH, 1: 1) extracts of C. calcitrapa leaves and their potential toxicity on MRC-5 cell line were investigated for the first time. A total of 55 phenolic compounds were identified: 30 phenolic acids and their derivatives, 25 flavonoid glycosides and aglycones. This is also the first report of the presence of centaureidin, jaceidin, kaempferide, nepetin, flavonoid glycosides, phenolic acids and their esters in C. calcitrapa extracts. The best results were obtained with EtOAc extract with lowest MIC values expressed in µg/mL ranging from 13 to 25, while methicillin resistant Staphylococcus aureus was the most susceptible strain. The most susceptible phytopathogens were Pseudomonas syringae pv. syringae, Xanthomonas campestris pv. campestris and Agrobacterium tumefaciens. The highest cytotoxicity was recorded for EtOAc and Me₂CO extracts with the lowest relative and absolute IC₅₀ values between 88 and 102 µg/mL, while EtOH extract was the least toxic with predicted relative IC₅₀ value of 1578 µg/mL. Our results indicate that all tested extracts at concentration considered as non-toxic can be one of great importance in combat towards phytopathogenic and human pathogenic strains, as well as natural sources of antimicrobials.

Antioxidant, Anti-Inflammatory and Cytotoxic Properties of Centaurea africana Lamk var. [Bonnet] M]

BACKGROUND

In Algerian traditional medicine, Centaurea species are well known in traditherapy. Centaurea africana has been used in folk medicine for the treatment of several inflammatory disorders.

OBJECTIVE

This study aims to examine the antioxidant, anti-inflammatory and anti-proliferative potential of both n-Butanol (BECA) and ethyl acetate (EAECA) extracts of Centaurea africana.

METHODS

The phytochemical analysis of both BECA and EAECA were explored and the antioxidant activities were investigated by measuring the DPPH° scavenging effect, the reducing power and the inhibition of lipid peroxidation (LPO) induced by by Fe²⁺/ ascorbic acid system. The antiinflammatory properties were determined by measuring the NO° scavenging effect and by using carrageenan-induced rat paw oedema. The antiproliferative activity was studied on HT29 (human colorectal adenocarcinoma), OV2008 (human ovarian cancer) and C6 (Rattus norvegicus brain glioma) cell lines using the Sulforhodamine B assay.

RESULTS

The total polyphenol contents (TPC) of EAECA and BECA are recorded at 125.24±10.14 and 53.03±2.50 mgGAE/g extract, respectively. Both extracts revealed the antioxidant activity in a concentration-dependent manner; this effect is more pronounced with EAECA. The BECA exhibited a higher anti-inflammatory activity. This anti-inflammatory activity was reflected in a reduction of swelling of carrageenan-evoked edemas (48.45 %), inhibition of nitric oxide (84.7 %), effective decrease in myeloperoxidase activity (58.82 %) and malondialdehyde level (65.58 %). The cytotoxic effect of BECA was found to be more pronounced against C6 cell lines (IC₅₀ value: 131.93 μg/mL) while the cytotoxic activity of EAECA was more effective against HT29 and OV2008 cell lines.

CONCLUSION

The obtained results indicated that EAECA exhibited a high antioxidant activity, while BECA has significant anti-inflammatory activity. Both extracts showed cytotoxic effects against cancer cell lines at certain concentrations in a cell-specific manner.

New γ-Halo-δ-lactones and δ-Hydroxy-γ-lactones with Strong Cytotoxic Activity

This paper presents the synthesis of γ -halo- δ -lactones, δ -iodo- γ -lactones and δ -hydroxy- γ -lactones from readily available organic substrates such as trans-crotonaldehyde and aryl bromides. Crystal structure analysis was carried out for lactones that were obtained in crystalline form. All halo- δ -lactones and δ -hydroxy- γ -lactones were highly cytotoxic against gastric cancer AGS cells with I C 50 values in the range of 0.0006-0.0044 mM. Some lactones showed high bactericidal activity against E. coli ATCC 8739 and S. aureus ATCC 65389, which reduced the number of CFU/mL by 70-83% and 87% respectively.

Antifeedant and Phagostimulant Activity of Extracts and Pure Compounds from Hymenoxys robusta on Spodoptera exigua (Lepidoptera: Noctuidae) Larvae

In this study, the insecticidal and antifeedant activities of compounds from the leaves of Hymenoxys robusta on Spodoptera exigua, also known as armyworm, are reported. The methanol extract possessed suppressive activity, as well as a high antifeedant activity, suggesting that this extract has toxic effects on larvae. Compounds isolated from the plant show that a derivative of inositol and hymenolides stimulate the feeding, while vermeerin shows a high antifeedant effect. In addition, the methanol extract inhibited oviposition, whereas consumption of the n-hexane extract and hymenolides produced infertile eggs. These findings suggest that compounds extracted from H. robusta have potential for the development of products for pest control.