Phenolic molecules represent one of the most prevalent and biologically important categories of secondary metabolites. Within this diverse group, phenolic acids and flavonoids are the most extensively studied categories, primarily due to their structural diversity and broad spectrum of reported bioactivities. We first provide an overview of the physicochemical characteristics of flavonoids and phenolic acids and discuss how these properties relate to mass spectrometry (MS) fragmentation patterns and chromatographic behavior, including retention characteristics and isomer resolution. Next, we systematically examine the utilization of MS-based procedures for the characterization of flavonoids and phenolic acids in complex natural matrices. We initially examine targeted liquid chromatography–tandem mass spectrometry (LC–MS/MS) utilizing triple-quadrupole (QQQ) platforms, focusing on selected/multiple reaction monitoring (SRM/MRM) and associated scanning techniques (product-ion and precursor-ion scans). We summarize validated methodologies and strategies for both absolute and relative quantification, including stable-isotope dilution, matrix-matched calibration or standard addition, and internal-standard normalization. We subsequently analyze untargeted high-resolution mass spectrometry methodologies (direct injection and coupled to liquid chromatography), highlighting recent progress in data acquisition while addressing ongoing challenges in computational processing. Finally, we present a brief evaluation of commonly used extraction and clean-up processes, highlighting their practical impact on phenolic recoveries.

Laurus nobilis L., Lauraceae, bay laurel, has been traditionally used for its various therapeutic properties, and in recent years has been gaining interest for its potential applications in skincare products. However, the biological effects of bay laurel, particularly its hydrosols, a water fraction obtained during essential oil production, remain unexplored. The objective of this study was to identify the volatile compounds in L. nobilis hydrosols (LnHYs) from different coastal regions of Croatia (north, middle, and south Adriatic) and to evaluate their potential safety and efficacy for dermatological applications. Upon isolating LnHYs using microwave-assisted extraction, LnHY volatiles were identified and quantified using gas chromatography and mass spectrometry. Oxygenated monoterpenes were the dominant compounds in all LnHYs (61.72–97.00%), with 1,8-cineole being the most abundant component (52.25–81.89%). The physical and chemical parameters of LnHYs were investigated to assess their purity and quality. Biological activity (cytotoxicity and wound-healing effect) was tested on the human keratinocyte cell line (HaCaT), selected as the experimental model due to its relevance to skin biology. Additionally, contents of polyphenolic substances, antioxidative effects using the Oxygen Radical Absorbance Capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods, and the antimicrobial activity of LnHYs toward five skin microorganisms were determined. All tested hydrosols showed similar biological activity, with only minor differences. Cytotoxicity studies indicated the safety of the dermatological application of LnHYs, and the results of the wound-healing assay showed their neutral to mildly positive effect. Considering the growing use of bay laurel preparations in pharmaceutical and cosmetic applications, extensive studies on their biological activity, quality, and safety are essential to either support or regulate their use in humans.

Ozone is a triatomic allotropic modification of oxygen with very high oxidation potential and strong antimicrobial properties, and can be used as a disinfecting agent. The aim of this work was to investigate the effectiveness of gaseous ozone in reducing the number of bacteria and the total biomass of E. coli biofilm using different methods of quantification and detection. Biofilm of all tested clinical isolates and standard strain was grown on ceramic tiles with dimensions of 1.0 × 1.0 cm over 24 h. These plates were then treated with gaseous ozone for 1 h. After washing, CFU/cm² was determined, ATP bioluminescence was measured with a luminometer, and the total biomass reduction was measured after crystal-violet staining. Gaseous ozone proved to be very effective in destroying the created bacterial biofilm on ceramic tiles. Treatment caused a reduction in total bacteria number of up to 2.00 log₁₀CFU/cm², followed by a reduction in total biomass of up to 61.40%. Inhibition rates varied from 35.80% to 99.41%, depending on the method of quantification used. All methods used in this study are effective in determining the anti-biofilm activity of gaseous ozone, but more research is needed.

Honeydew honey (HH) is a distinctive type of honey known for its dark colour, high mineral and polyphenol content, and pronounced biological activity. This study continues previous research on beech and chestnut honeydew honeys by presenting a comprehensive analysis of linden honeydew honey (LHH) from Bosnia and Herzegovina—a variety that, until now, has not been characterised in detail. Physicochemical parameters confirmed its classification as HH, with high electrical conductivity (1.21 mS/cm) and low moisture (15.1%). GC-MS analysis revealed a unique volatile profile dominated by α-terpinolene (17.4%), distinguishing LHH from other HH types. The sample exhibited high total phenolic content (816.38 mg GAE/kg) and moderate antioxidant capacity (1.11 mmol TE/kg). Antimicrobial testing demonstrated strong activity against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA), with lower efficacy against Gram-negative bacteria. No cytotoxic effects were observed in HaCaT keratinocytes at concentrations up to 60 mg/mL, and wound healing assays showed improved scratch closure reaching approximately 30% after 24 h and 41% after 48 h compared to the control. These results indicate that LHH possesses promising bioactive properties and potential for dermatological application. Further studies with broader sample sets are needed to explore variability and confirm the therapeutic relevance of LHH in comparison to other honeydew types.

The group of nontuberculous mycobacteria (NTM) includes about 200 mycobacteria that are widespread in the natural environment as free-living saprophytic bacteria, commensals or symbionts. NTM, also referred to as atypical mycobacteria, are mostly apathogenic; nowadays, they are increasingly important environmental opportunistic pathogens. This study continues the work of previous studies which investigated the individual and synergistic effect of different essential oils (EOs) on NTM. The aim was to investigate the effect of the interaction of the common juniper (Juniperus communis) EO and the antimicrobials, amikacin, clarithromycin and rifampicin, against Mycobacterium avium and M. intracellulare using the checkerboard synergy method in an enriched Middlebrook 7H9 broth. Morphological changes of treated NTM cells were observed with a transmission electron microscope. The most synergistic combinations were found at subinhibitory concentrations of the common juniper EO and rifampicin against both tested NTM and this EO and clarithromycin against M. avium. A slightly smaller number of synergistic effects on both NTM were found using a combination of this EO and amikacin. Combinations of clarithromycin and the common juniper EO showed no synergism against M. intracellulare. The exposure of both NTM to synergistic combinations of this EO and antimicrobials caused significant morphological changes in mycobacterial cells. Synergism with the combined use of EOs and antimicrobials allows the use of low effective concentrations via the sustained antimicrobial effect of the tested substances, but with potentially reduced toxicity.