Synthesis and antimicrobial activity of some new 4-hydroxy-2H- 1,4-benzoxazin-3(4H)-ones

Antiproliferative activity of antimicrobial peptides and bioactive compounds from the mangrove Glutamicibacter mysorens

The Glutamicibacter group of microbes is known for antibiotic and enzyme production. Antibiotics and enzymes produced by them are important in the control, protection, and treatment of chronic human diseases. In this study, the Glutamicibacter mysorens (G. mysorens) strain MW647910.1 was isolated from mangrove soil in the Mangalore region of India. After optimization of growth conditions for G. mysorens on starch casein agar media, the micromorphology of G. mysorens was found to be spirally coiled spore chain, each spore visualized as an elongated cylindrical hairy appearance with curved edges visualized through Field Emission Scanning Electron Microscopy (FESEM) analysis. The culture phenotype with filamentous mycelia, brown pigmentation, and ash-colored spore production was observed. The intracellular extract of G. mysorens characterized through GCMS analysis detected bioactive compounds reported for pharmacological applications. The majority of bioactive compounds identified in intracellular extract when compared to the NIST library revealed molecular weight ranging below 1kgmole^-1. The Sephadex G-10 could result in 10.66 fold purification and eluted peak protein fraction showed significant anticancer activity on the prostate cancer cell line. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis revealed Kinetin-9-ribose and Embinin with a molecular weight below 1 kDa. This study showed small molecular weight bioactive compounds produced from microbial origin possess dual roles, acting as antimicrobial peptides (AMPs) and anticancer peptides (ACPs). Hence, the bioactive compounds produced from microbial origin are a promising source of future therapeutics.

Synthesis and Reactivity of 6,8-Dibromo-2-ethyl-4H-benzo[d][1,3]oxazin-4-one Towards Nucleophiles and Electrophiles and Their Anticancer Activity

BACKGROUND

The genetic heterogeneity of tumor cells and the development of therapy-resistant cancer cells in addition to the high cost necessitate the continuous development of novel targeted therapies.

METHODS

In this regard, 14 novel benzoxazinone derivatives were synthesized and examined for anticancer activity against two human epithelial cancer cell lines; breast MCF-7 and liver HepG2 cells. 6,8-Dibromo-2- ethyl-4H-benzo[d][1,3]oxazin-4-one was subjected to react with nitrogen nucleophiles to afford quinazolinone derivatives and other related moieties (3-12). Benzoxazinone 2 responds to attack with oxygen nucleophile such as ethanol to give ethyl benzoate derivative 13. The reaction of benzoxazinone 2 with carbon electrophile such as benzaldehyde derivatives afforded benzoxazinone derivatives 14a and 14b.The structure of the prepared compounds was confirmed with spectroscopic tools including IR, 1H-NMR, and 13C-NMR.

RESULTS

Derivatives 3, 9, 12, 13, and 14b exhibited high antiproliferative activity and were selective against cancer cells showing no toxicity in normal fibroblasts. Derivative 3 with NH-CO group in quinazolinone ring was effective only against breast cells, while derivative 12 with NH-CO group in imidazole moiety was only effective against liver cells probably through arresting cell cycle and enabling repair mechanisms. The other derivatives (9, 13, and 14b) had broader antiproliferative activity against both cell lines. These derivatives enhance the expression of the p53 and caspases 9 and 3 to varying degrees in both cell lines. Derivative 14b caused the highest induction in the investigated genes and was the only derivative to inhibit the EGFR activity.

CONCLUSIONS

The unique features about derivative 14b could be attributed to its high lipophilicity, high carbon content, or its extended conjugation through planar aromatic system. More investigations are required to identify the lead compound(s) in animal models.

QSAR of 1,4-benzoxazin-3-one antimicrobials and their drug design perspectives

Synthetic derivatives of 1,4-benzoxazin-3-ones have been shown to possess promising antimicrobial activity, whereas their natural counterparts were found lacking in this respect. In this work, quantitative structure-activity relationships (QSAR) of natural and synthetic 1,4-benzoxazin-3-ones as antimicrobials were established. Data published in literature were curated into an extensive dataset of 111 compounds. Descriptor selection was performed by a genetic algorithm. QSAR models revealed differences in requirements for activity against fungi, gram-positive and gram-negative bacteria. Shape, VolSurf, and H-bonding property descriptors were frequently picked in all models. The models obtained for gram-positive and gram-negative bacteria showed good predictive power (Q²_Ext 0.88 and 0.85, respectively). Based on the models generated, an additional set of 1,4-benzoxazin-3-ones, for which no antimicrobial activity had been determined in literature, were evaluated in silico. Additionally, newly designed lead compounds with a 1,4-benzoxazin-3-one scaffold were generated in silico by varying the positions and combinations of substituents. Two of these were predicted to be up to 5 times more active than any of the compounds in the current dataset. The 1,4-benzoxazin-3-one scaffold was concluded to possess potential for the design of new antimicrobial compounds with potent antibacterial activity, a multitarget mode of action, and possibly reduced susceptibility to gram negatives' efflux pumps.

Structure and biosynthesis of benzoxazinoids: Plant defence metabolites with potential as antimicrobial scaffolds

Benzoxazinoids, comprising the classes of benzoxazinones and benzoxazolinones, are a set of specialised metabolites produced by the plant family Poaceae (formerly Gramineae), and some dicots. The family Poaceae in particular contains several important crops like maize and wheat. Benzoxazinoids play a role in allelopathy and as defence compounds against (micro)biological threats. The effectivity of benzoxazinones in these functionalities is largely imposed by the subclasses (determined by N substituent). In this review, we provide an overview of all currently known natural benzoxazinoids and a summary of the current state of knowledge of their biosynthesis. We also evaluated their antimicrobial activity based on minimum inhibitory concentration (MIC) values reported in literature. Monomeric natural benzoxazinoids seem to lack potency as antimicrobial agents. The 1,4-benzoxazin-3-one backbone, however, has been shown to be a potential scaffold for designing new antimicrobial compounds. This has been demonstrated by a number of studies that report potent activity of synthetic derivatives of 1,4-benzoxazin-3-one, which possess MIC values down to 6.25 μg mL^-1 against pathogenic fungi (e.g. C. albicans) and 16 μg mL^-1 against bacteria (e.g. S. aureus and E. coli). Observations on the structural requirements for allelopathy, insecticidal, and antimicrobial activity suggest that they are not necessarily conferred by similar mechanisms.

Sonochemical synthesis of novel pyrano[3,4-e][1,3]oxazines: A green protocol

The atom-efficient and green protocol for formation of pyrano[3,4-e][1,3]oxazines utilizing dimethyl carbonate under ultrasound irradiation in a presence of KF/basic alumina was reported. We provide a novel series of pyrano[3,4-e][1,3]oxazine derivatives interesting for biological screening tests. In general, it was found that ultrasound irradiations enable the reactions to occur which could not be carried out under silent conditions. These remarkable effects appeared in sonicated reactions can be reasonably interpreted in terms of acoustic cavitation phenomenon. Structures of the products were established on analytical and spectral data. This protocol offers several advantages attain many principles of green chemistry including, save energy, atom economy, clean reactions, inexpensive green reagent and use catalysts rather than stoichiometric reagents.

Synthesis and antifungal activity of 2H-1,4-benzoxazin-3(4H)-one derivatives

A series of 2-alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-l) was easily synthesized by two-step process involving O-alkylation of 2-nitrophenols with methyl 2-bromoalkanoates and next "green" catalytic reductive cyclization of the obtained 2-nitro ester intermediates (3a-l). Further, 6,7-dibromo (5a-c) and N-acetyl (6) derivatives were prepared by bromination and acetylation of unsubstituted 2-alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-c). The novel compounds (3a-l, 4d-l, 5a-c and 6) were fully characterized by spectroscopic methods (MS, (1)H and (13)C NMR). 2-Alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-l, 5a-c and 6) were screened for antifungal activity. Preliminary assays were performed using two methods: in vitro against seven phytopathogenic fungi-Botrytis cinerea, Phythophtora cactorum, Rhizoctonia solani, Phoma betae, Fusarium culmorum, Fusarium oxysporum and Alternaria alternata-and in vivo against barley powdery mildew Blumeria graminis. The tested compounds displayed moderate to good antifungal activity at high concentration (200 mg L(-1)). The most potent compounds were 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a), 2-ethyl-7-fluoro-2H-1,4-benzoxazin-3(4H)-one (4g) and 4-acetyl-2-ethyl-2H-1,4-benzoxazin-3(4H)-one (6), which completely inhibited the mycelial growth of seven agricultural fungi at the concentration of 200 mg L(-1) in the in vitro tests. Moreover, 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a) and 4-acetyl-2-ethyl-2H-1,4-benzoxazin-3(4H)-one (6) were also screened for antifungal activity at concentrations of 100 mg L(-1) and 20 mg L(-1). In the concentration of 100 mg L(-1), the N-acetyl derivative (6) completely inhibited the growth of three strains of fungi (F. culmorum, P. cactorum and R. solani), while 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a) completely inhibited only R. solani strain. At the concentration of 20 mg L(-1), compound 6 showed good activity only against P. cactorum strain (72%).

New herbicide models from benzoxazinones: aromatic ring functionalization effects

The utility of benzoxazinones and some of their synthetic derivatives in the search for new leads for herbicide model development has been widely discussed. As the benzoxazinone skeleton contains three different potential areas for functionalization (C-2, N-4, and aromatic protons H-5, H-6, H-7, and H-8), and the first two have already been optimized, the main objective of this work was the substitution of aromatic protons for different substituent types and the study of the effects of the prepared chemicals on selected standard target species (STS) and weeds. Thus, different combinations of aromatic substituents, including methoxy, methoxycarbonyl, fluorine, chlorine, and trifluoromethyl, were introduced at different positions. Phytotoxicity results were successfully correlated with steric and electronic molecular parameters, the resulting molecular volume (V) and dipole moment (mu) being the most influential ones. Halogenations at C-6 and fluorination at C-7 were the most successful modifications. Compounds 6-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (6F-D-DIBOA), 7-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (7F-D-DIBOA), and 6-chloro-(2H)-1,4-benzoxazin-3(4H)-one (6Cl-D-DIBOA) had the highest phytotoxic activities. The dose-response profiles on wheat and two of its most common weeds (Lolium rigidum Gaud. and Avena fatua L.) were compared by means of a proposed selectivity index, which displayed 7F-D-DIBOA as the most selective of the tested benzoxazinones.

Synthesis of Diverse Benzo[1,4]oxazin-3-one-Based Compounds Using 1,5-Difluoro-2,4-dinitrobenzene

This paper discusses the synthesis of benzo[1,4]oxazin-3-one-based compounds from 1,5-difluoro-2,4-dinitrobenzene (1), including benzo[1,4]oxazin-3-ones (5-11) and five novel benzo[1,4]oxazin-3-one-based tricycles: 6-hydroxy-4H-1-oxa-4,5,8-triazaanthracen-3-one (14), 3,8-dihydro-5-oxa-1,3,8-triazacyclopenta-[b]-naphthalene-7-one (15, 17, 21), 3,8-dihydro-5-oxa-1,2,3,8-tetraazacylopenta[b]-naphthalene-7-one (16, 20), 3,8-dihydro-1H-5-oxa-1,3,8-triazacyclopenta[b]-naphthalene-2,7-dione (18, 22), and 5,8-dihydro-4H-1-oxa-4,5,8-triazaanthracene-3,6,7-trione (19). Finally, a chemical library based on 15 was synthesized in parallel solution-phase reactions.

Synthesis, antimicrobial activity and QSARs of new benzoxazine-3-ones

New ethyl 3,4-dihydro-3-oxo-4,6,7-trisubstituted-2H-1,4-benzoxazine-2-acetate derivatives were synthesized and their structures were elucidated by IR, (1)H NMR and mass spectral data. Antimicrobial activity of the compounds was investigated by using the method of twofold serial dilution technique against different Gram-positive, Gram-negative bacteria and some Candida species in comparison to standard drugs. Microbiological results indicated that the synthesized compounds possessed a broad spectrum of activity having MIC values of 6.25-100 micro g/ml against the tested microorganisms. The QSAR analysis of a set of these compounds tested for growth inhibitory activity against Candida krusei was performed by using the computer-assisted multiple regression procedure. The activity contributions for substituent effects of these compounds were determined from the correlation equation for predictions of the lead optimization.