Evaluation of mutagenicity and metabolism-mediated cytotoxicity of the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin from Paepalanthus latipes

Synthesis of Eugenol Derivatives and Evaluation of their Antifungal Activity Against Fusarium solani f. sp. piperis

BACKGROUND

Fusarium solani f. sp. piperis is a phytopathogen that causes one of the most destructive diseases in black pepper crops, resulting in significant economic and crop production losses. Consequently, the control of this fungal disease is a matter of current and relevant interest in agriculture.

OBJECTIVE

The objective was to synthesize eugenol derivatives with antifungal activity.

METHODS

In this study, using bimolecular nucleophilic substitution and click chemistry approaches, four new and three known eugenol derivatives were obtained. The eugenol derivatives were characterized and their antifungal and cytotoxic effects were evaluated.

RESULTS

Eugenol derivative 4 (2-(4-allyl-2-methoxyphenoxy)-3-chloronaphthalene-1,4-dione) was the most active against F. solani f. sp. piperis and showed acceptable cytotoxicity. Compound 4 was two-fold more effective than tebuconazole in an antifungal assay and presented similar cytotoxicity in macrophages. The in silico study of β-glucosidase suggests a potential interaction of 4 with amino acid residues by a cation-π interaction with residue Arg177 followed by a hydrogen bond with Glu596, indicating an important role in the interactions with 4, justifying the antifungal action of this compound. In addition, the cytotoxicity after metabolism was evaluated as a mimic assay with the S9 fraction in HepG2 cells. Compound 4 demonstrated maintenance of cytotoxicity, showing IC50 values of 11.18 ± 0.5 and 9.04 ± 0.2 μg mL-1 without and with the S9 fraction, respectively. In contrast, eugenol (257.9 ± 0.4 and 133.5 ± 0.8 μg mL-1), tebuconazole (34.94 ± 0.2 and 26.76 ± 0.17 μg mL-1) and especially carbendazim (251.0 ± 0.30 and 34.7 ± 0.10 μg mL-1) showed greater cytotoxicity after hepatic biotransformation.

CONCLUSION

The results suggest that 4 is a potential candidate for use in the design of new and effective compounds that could control this pathogen.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

Antitumour, Immunomodulatory activity and in silico studies of naphthopyranones targeting iNOS, a relevant target for the treatment of Helicobacter pylori infection

The naphthopyranones paepalantine and 5-methoxy-3,4-dehydroxanthomegnin isolated from Paepalanthus sp, showed in previous studies antioxidant, anti-inflammatory, antitumour and antimicrobial potential, such as anti-Helicobacter pylori activity. H. pylori infection is one of the main causes of gastric cancer, causing an excessive inflammatory response through the neutrophils and macrophages infiltration, increasing the release of reactive species and thus inducing the production of pro-inflammatory mediators. In the present study, immunomodulatory activity of naphthopyranones in LPS-stimulated macrophages and cytotoxic action in gastric adenocarcinoma cell lines was evaluated. The potential of interaction of these substances in the iNOS binding site was investigated by molecular docking. Cytotoxic activity in gastric adenocarcinoma cells (AGS) was evaluated by the MTT assay. The results evidenced immunomodulatory potential by inhibiting the pro-inflammatory cytokines and nitric oxide produced by LPS-stimulated macrophages. Cytotoxic activity in AGS cell line was also reported. The results indicated that the studied naphthopyranones are viable alternatives in the treatment and prevention of H. pylori infection as well as the diseases related to this infection, especially gastric cancer.

Raphanus sativus Sprout Causes Selective Cytotoxic Effect on p53-Deficient Human Lung Cancer Cells in vitro

Raphanus sativus L. (Brassicaceae) is widely consumed in many different forms worldwide. Its sprouts, in particular, are commonly consumed as a health food. R. sativus sprout has recently been shown to have anti-tumor activity on human colon cancer cells, suggesting that it may have potential use in cancer prevention and treatment. The extent of this anti-tumor activity and its underlying mechanisms, however, remain to be investigated in other types of cancer cells. In this study, we showed that the MeOH extract from R. sativus sprout exhibits significant but variable cytotoxic effects on human lung adenocarcinoma cells depending on their p53 status. The MeOH extract decreased the viability of p53-deleted human lung cancer cells (H1299 and Calu-6) by inducing apoptosis; this effect, however, did not occur for wild-type p53 cancer cells (A549), for cells expressing a p53 mutant lacking the C terminus (H1264), or for non-tumor fibroblast cells (NIH3T3). Phytochemical analyses of the MeOH extract allowed us to identify and isolate β-sitosterol as a major component of the MeOH extract. Direct treatment with β-sitosterol significantly reduced the viability of Calu-6 cells, suggesting that it may, in part, contribute to R. sativus sprout's anti-tumor activity. This work provides experimental evidence for a novel biological application of R. sativus sprout in treating human lung cancer, and it identifies the main component involved in this effect, further supporting its potential use as a functional food for cancer management.

Effect of biotransformation by liver S9 enzymes on the mutagenicity and cytotoxicity of melanin extracted from Aspergillus nidulans

CONTEXT

A mutant that exhibited increased melanin pigment production was isolated from Aspergillus nidulans fungus. This pigment has aroused biotechnological interest due to its photoprotector and antioxidant properties. In a recent study, we showed that melanin from A. nidulans also inhibits NO and TNF-α production.

OBJECTIVE

The present study evaluates the mutagenicity and cytotoxicity of melanin extracted from A. nidulans after its exposure to liver S9 enzymes.

MATERIALS AND METHODS

The cytotoxicity of multiple concentrations of melanin (31.2-500 μg/mL) against the McCoy cell line was evaluated using the Neutral Red assay, after incubation for 24 h. Mutagenicity was assessed using the Ames test with the Salmonella typhimurium strains TA98, TA97a, TA100, and TA102 at concentrations ranging from 125 μg/plate to 1 mg/plate after incubation for 48 h.

RESULTS

The cytotoxicity of A. nidulans melanin after incubation with S9 enzymes was less than (CI50 value= 413.4 ± 3.1 μg/mL) that of other toxins, such as cyclophosphamide (CI50 value = 15 ± 1.2 μg/mL), suggesting that even the metabolised pigment does not cause significant damage to cellular components at concentrations up to 100 μg/mL. In addition, melanin did not exhibit mutagenic properties against the TA 97a, TA 98, TA 100, or TA 102 strains of S. typhimurium, as shown by a mutagenic index (MI)  <2 in all assays.

DISCUSSION AND CONCLUSION

The significance of these results supports the use of melanin as a therapeutic reagent because it possesses low cytotoxicity and mutagenic potential, even when processed through an external metabolising system.