New quercetin-based derivatives are synthesized in an easily accessible one-pot manner. The method is based on the reaction of quercetin with in situ formed electrophilic N-alkoxycarbonylazolium ions. The position of the newly formed C-C bond and structure were spectrally characterized by 1D, 2D ¹H, ¹³C-NMR, IR, and MS analysis. Thus, in all cases, good regioselectivity in the C-8 position for the obtained products was demonstrated. The obtained compounds were evaluated for their DPPH and ABTS free radical scavenging activity and compared to natural compounds—quercetin and rutin.

N-acyliminium reagents formed in situ from benzothiazole and alkyl chloroformates react with hydroxyarenes in a Friedel-Crafts manner, providing access to 2-(hydroxyaryl)-benzothiazolines with antibacterial properties.

The Thymus vulgaris and Origanum vulgare essential oils (contained thymol and carvacrol in a range of 35–80%) are used in various products in the fields of medicine, cosmetics, and foods. Molecular hybridization between benzothiazole (BT) and phenolic monoterpenoids is a promising method for the development of biologically active compounds. New benzothiazole–monoterpenoid hybrids were synthesized through a regioselective α-amidoalkylation reaction of thymol and carvacrol with high yields (70–96%). This approach is both simple and cost-effective, employing easily accessible and inexpensive reagents to produce target molecules. The structure of the synthesized compounds was characterized spectrally using ¹H-, ¹³C-NMR, FT-IR, and HRMS data. The newly obtained compounds are structural analogues of the UVB filter PBSA, which is used in cosmetics. The spectral properties of the aromatic products thymol hybrid (2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole) and carvacrol hybrid (2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole) were successfully examined, using a validated spectrophotometric method. SPF values varied from 31 to 36, compared to the PBSA (30), and were observed at concentrations of 1–0.25 mM. 2-Hydroxyphenylbenzothiazoles are known antimicrobial and antioxidant agents that have potential applications in the food industry and cosmetics as preservatives and antioxidants. In this context, antimicrobial activity of the hybrid compounds was evaluated using the agar diffusion method against E. coli, S. aureus, P. aeruginosa, and C. albicans. Compounds of methyl-2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate containing carvacrol fragments showed high activity against Staphylococcus aureus ATCC 25923 (with 0.044 μmol content). The radical scavenging activity was determined using ABTS and DPPH assays, the highest activity was exhibited by the thymol hybrids ethyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—133.70 ± 10 µM) and methyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—157.50 ± 10 µM), defined by ABTS. The aromatic benzothiazole–monoterpenoid hybrids are classified using in silico analyses as non-mutagenic, with low toxicity, and they are non-irritating to the skin. These compounds were identified as new hit scaffolds for multifunctional molecules in cosmetics.

New 2-(2,4-dihydroxyphenyl)benzimidazolines are synthesized in an easily accessible approach. The method is based on the reaction of resorcinol with in situ-formed electrophilic N-ethoxycarbonylbenzimidazolium reagents. The structure of the two newly formed products was spectrally characterized by 1D and 2D NMR, IR, and MS spectral analyses.

This study aimed to determine the total phenolic content of Oriental tobacco waste seeds, grown under organic production, and to evaluate their antioxidant activity by extraction with different solvents under different conditions. The extraction was performed with H2O, 99.9% CH3OH, 60% CH3OH, and 96% C2H5OH under maceration and ultrasonic extraction at 20°C and 40°C. All solvents were used in a volume of 4 mL, 5 mL, and 6 mL. The total phenolic content varied between 0.89 mg/g GAE (maceration; sample/solvent ratio 0.1g/5mL, C2H5OH) and 5.85 mg/g GAE (maceration; sample/solvent ratio 0.1g/6mL, C2H5OH). Ethanolic and 60% methanolic extracts had the highest antioxidant activity as determined by the DPPH method; 60% methanolic and water extracts had the highest antioxidant activity as determined by the ABTS method; while methanolic and 60% methanolic extracts had the highest antioxidant activity as determined by the FRAP method. In addition, the content of nicotine in tobacco seed extract was not detected.