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The quinone avarone, isolated from the marine sponge Dysidea avara, possesses the ability to chemically modify proteins. In this work, modification of lectin isolated from the coral Gerardia savaglia by avarone was examined. The techniques used for studying the modification were: SDS PAGE, isoelectric focusing and hemagglutination testing. The results of the SDS PAGE indicate dimerization of the protein. A shift of the pI toward lower value occurs upon modification. The change of the hemagglutination activity of the protein confirms that chemical modification of G. savaglia lectin by avarone changes its ability to interact with the membrane of erythrocytes.

Amyloglucosidase from A. niger was covalently immobilized onto poly (GMA-co-EGDMA) by the glutaraldehyde and periodate method. The immobilization of amyloglucosidase after periodate oxidation gave a preparate with the highest specific activity reported so far on similar polymers. The obtained immobilized preparates show the same pH optimum, but a higher temperature optimum compared with the soluble enzyme. The kinetic parameters for the hydrolysis of soluble starch by free and both immobilized enzymes were determined.

The avarone/avarol quinone/hydroquinone couple shows considerable antitumor activity. In this work, covalent modification of b-lactoglobulin by avarone and its derivatives as well as by the synthetic steroidal quinone 2,5(10)-estradiene-1,4,17-trione and its derivatives were studied. The techniques for studying chemical modification of b-lactoglobulin by quinones were: UV/Vis spectrophotometry, SDS PAGE and isoelectrofocusing. SDS PAGE results suggest that polymerization of the protein occurs. It could be seen that the protein of 18 kD gives the bands of 20 kD, 36 kD, 40 kD, 45 kD, 64 kD and 128 kD depending on modification agent. The shift of the pI of the protein (5.4) upon modification toward lower values (from pI 5.0 to 5.3) indicated that lysine amino groups are the principal site of the reaction of b-lactoglobulin with the quinones.

The avarone/avarol quinone/hydroquinone couple, as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of b-lactoglobulin, isolated from cow milk, by avarone, its model compound 2-tert-butyl-1,4-benzoquinone, and several of their alkylthio derivatives were studied. The techniques applied for assaying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of the reaction of b-lactoglobulin with the quinones.

The regioselectivity of the reaction of conjugate addition of thiols, amines, methanol and hydrogen chloride with the monoalkyl-1,4-benzoquinones avarone and 2-tert-butyl-1,4-benzoquinone was investigated. It was shown that the regioselectivity of the reaction is influenced by the electrophilicity of position 5 in unprotonated 2-alkylquinones, the increased electrophilicity of position 6 in acidic medium, and by the acidity of the intermediate hydroquinones.

Basil (Ocimum basilicum L.) is a widely used culinary herb. In this study, ethanol, dichloromethane, and sunflower oil were used separately as solvents with distinct polarities for the extraction of basil aerial parts to simulate the different polarity conditions in domestic food processing. The oil extract (OE) was re-extracted with acetonitrile, and the chemical composition, antioxidant potential, and antimicrobial activities of the ethanol (EE), dichloromethane (DCME), and acetonitrile (ACNE) extracts were determined. A total of 109 compounds were tentatively identified in EE, DCME, and ACNE by HPLC–DAD/ESI-ToF-MS. Fatty acids were present in all extracts. Phenolic acids and flavonoids dominated in EE. DCME was characterised by triterpenoid acids, while diterpenoids were mainly found in ACNE. The extracts were analysed for their antioxidant capacity using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. EE and DCME showed significant radical scavenging potential. Antimicrobial activity was explored in eight bacterial, two yeast, and one fungal species. All extracts exhibited high antifungal activity, comparable to or better than that of the commercial drug nistatin. Antibacterial activities were notable for EE and ACNE, while DCME showed no activity against bacteria in the applied concentration ranges. The different polarities of the solvents led to distinctive phytochemical compositions and bioactivities in the extracts.

Helichrysum plicatum DC. is widely used in folk medicine in treating a variety of health disorders. The aim of this study was to examine the influence of different extraction solvents on the chemical composition, antioxidant potential, and antimicrobial activities of H. plicatum. Aerial parts were separately extracted with ethanol, dichloromethane, and sunflower oil. The oil extract (OE) was re-extracted with acetonitrile. A total of 142 compounds were tentatively identified in ethanolic (EE), dichloromethane (DCME), and acetonitrile (ACNE) extracts using HPLC-DAD/ESI-ToF-MS. The dominant compound class in all extracts were α-pyrones, alongside flavonoids in EE, terpenoids in DCME and ACNE, and phloroglucinols in DCME. The antioxidant potential of the extracts was assessed by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. EE and DCME possessed the most potent radical scavenging capacity. Antimicrobial activity was investigated on eight bacterial, two yeast, and one fungal species. All extracts exhibited high antifungal and notable antibacterial activities compared to control substances, with DCME being the most potent. DCME exhibited stronger antimicrobial activity against P. aeruginosa than the standard chloramphenicol.

Thymoquinone (TQ), a natural compound with antimicrobial and antitumor activity, was used as the starting molecule for the preparation of 3-aminothymoquinone (ATQ) from which ten novel benzoxazole derivatives were prepared and characterized by elemental analysis, IR spectroscopy, mass spectrometry and NMR (1H, 13C) spectroscopy in solution. The crystal structure of 4-methyl-2-phenyl-7-isopropyl-1,3-benzoxazole-5-ol (1a) has been determined by X-ray diffraction. All compounds were tested for their antibacterial, antifungal and antitumor activities. TQ and ATQ showed better antibacterial activity against tested Gram-positive and Gram-negative bacterial strains than benzoxazoles. ATQ had the most potent antifungal effect against Candida albicans, Saccharomyces cerevisiae and Aspergillus brasiliensis. Three benzoxazole derivatives and ATQ showed the highest antitumor activities. The most potent was 2-(4-fluorophenyl)-4-methyl-7-isopropyl-1,3-benzoxazole-5-ol (1f). Western blot analyses have shown that this compound inhibited phosphorylation of protein kinase B (Akt) and Insulin-like Growth Factor-1 Receptor (IGF1R β) in HeLa and HepG2 cells. The least toxic compound against normal fibroblast cells, which maintains similar antitumor activities as TQ, was 2-(4-chlorophenyl)-4-methyl-7-isopropyl-1,3-benzoxazole-5-ol (1e). Docking studies indicated that 1e and 1f have significant effects against selected receptors playing important roles in tumour survival.

The sesquiterpene hydroquinone avarol (1) was isolated from the marine sponge Dysidea avara, whereas the corresponding quinone, avarone (2), was obtained by oxidation of avarol, and the significantly more lipophilic compounds [3’-(p-chloro-phenyl)avarone (3), 3’,4’-ethylenedithioavarone (4), 4’-isopropylthioavarone (5), 4’-tert-butylthioavarone (6), 4’-propylthioavarone (7), 4’-octylthioavarone (8)] were obtained by nucleophilic addition of thiols or p-chloroaniline to avarone. All these compounds were tested, at concentrations ranging from 0.5 to 50 μg/mL, for their effect on the settlement of the cyprid stage of Balanus amphitrite, for toxicity to both nauplii and cyprids and for their growth inhibitory activity on marine bacteria (Cobetia marina, Marinobacterium stanieri, Vibrio fischeri and Pseudoalteromonas haloplanktis) and marine fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata and Monodictys pelagica).