Study on Chemical Composition and Biological Activity of Psidium guajava Leaf Extracts.

Guava (Psidium guajava) is a plant widely distributed in tropical and subtropical regions. Its leaves contain a large amount of physiological molecules such as flavonoid, sesquiterpene, triterpenoid, coumarin, alkaloid, and tannin molecules with antioxidative and anti-inflammatory effects. In this study, the use of concentrated P. guajava leaf extract molecules as a functional natural material was evaluated by confirming the extract's antioxidative, antibacterial, tyrosinase activity inhibition, and collagenase activity inhibition effects and its trans-2-nonenal removal ability. As a result of the analysis of the antioxidant and antibacterial components of concentrated P. guajava leaf extract molecules through GC-MS, a large amount of aromatic hydrocarbon molecules were detected. When different concentrations of ethanol were used for extraction, the leaf extract concentrated with 70% ethanol showed the most effective active molecules. As a result of measuring DPPH radical scavenging activity, a concentration-dependent antioxidant activity was confirmed. The antioxidant activity tended to increase when the ethanol content used for extraction was increased. Molecules such as 2,4-di-tert-butylphenol, caryophyllene oxide, and γ-muurolene in P. guajava leaf extract concentrate appeared to have antibacterial activities against S. aureus bacteria known to cause atopy. As ethanol content increased, the inhibitory effect on tyrosinase activity was increased. In addition, when ethanol content was 50%, the concentrated leaf extract was able to remove trans-2-nonenal by 52.4%. As a result of determining the concentrated leaf extract's collagenase inhibition activity, an inhibition rate close to that of ascorbic acid, a positive control, was confirmed. The concentrated guajava leaf extract molecules were confirmed to have whitening and wrinkle-improving functionality. Thus, the P. guajava leaf extract has high potential as a food and natural cosmetic material.

Unveiling the bioactive potential of Actinomycetota from the Tagus River estuary.

The increase in global travel and the incorrect and excessive use of antibiotics has led to an unprecedented rise in antibiotic resistance in bacterial and fungal populations. To overcome these problems, novel bioactive natural products must be discovered, which may be found in underexplored environments, such as estuarine habitats. In the present work, estuarine actinomycetotal strains were isolated with conventional and iChip techniques from the Tagus estuary in Alcochete, Portugal, and analysed for different antimicrobial bioactivities. Extracts were produced from the isolated cultures and tested for bioactivity against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Aspergillus fumigatus ATCC 240305, Candida albicans ATCC 10231 and Trichophyton rubrum FF5. Furthermore, bioactive extracts were subjected to dereplication by high-performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS) to putatively identify their chemical components. In total, 105 isolates belonging to 3 genera were obtained. One which was isolated, MTZ3.1 T, represents a described novel taxon for which the name Streptomyces meridianus was proposed. Regarding the bioactivity testing, extracts from 12 strains proved to be active against S. aureus, 2 against E. coli, 4 against A. fumigatus, 3 against C. albicans and 10 against T. rubrum. Dereplication of bioactive extracts showed the presence of 28 known bioactive molecules, 35 hits have one or more possible matches in the DNP and 18 undescribed ones. These results showed that the isolated bacteria might be the source of new bioactive natural products.

Bee venom enhances performance and immune function in thinlip mullet: A promising approach for sustainable aquaculture.

As an environmentally friendly alternative to antibiotics, bee venom holds promise for aquaculture due to its diverse health advantages, including immune-amplifying and anti-inflammatory features. This study investigated the effects of dietary bee venom (BV) on the growth and physiological performance of Thinlip mullet (Liza ramada) with an initial body weight of 40.04 ± 0.11 g for 60 days. Fish were distributed to five dietary treatments (0, 2, 4, 6, and 8 mg BV/kg diet) with three replicates. Growth traits, gut enzyme ability (lipase, protease, amylase), intestinal and liver histology, blood biochemistry, immune responses [lysozyme activity (LYZ), bactericidal activity (BA), nitroblue tetrazolium (NBT%)], and antioxidant status [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), malondialdehyde (MDA)] were evaluated. BV supplementation significantly improved growth performance, digestive enzyme activity, histological integrity of organs, immune responses (LYZ, BA), and antioxidant status (SOD, CAT, GPx), while declining MDA levels. Optimal BV levels were identified between 4.2 and 5.8 mg/kg diet for different parameters. Overall, the findings suggest that BV supplementation can enhance growth and physiological performance in Thinlip mullet, highlighting its potential as a beneficial dietary supplement for fish health and aquaculture management.

Antimicrobial activity of eight plant essential oils having antioxidant property against spoilage microbes.

AIMS: To identify efficient, broad-spectrum, and non-toxic preservatives for natural agricultural products, eight essential oils were screened for high inhibitory and antioxidant activities against spoilage microbes. METHODS AND RESULTS: The zone of inhibition test and minimum inhibitory concentration (MIC) assay were performed to assess the antimicrobial activity of eight essential oils against B. subtilis, S. aureus, Penicillium, Saccharomyces, and E. coli. Among the eight essential oils, garlic and rose essential oils exhibited the best inhibitory effects, their MICs against the spoilage microbes were 40-640 µL/L and 10-320 µL/L, respectively. In addition, the antioxidant activities of eight essential oils were compared using the DPPH and ABTS radical-scavenging assays and the reducing power assay. eight essential oils had antioxidant capacity, among which rosemary, thyme, rose, and tea tree essential oils performed best. Moreover, the combination of thyme and rose exerted stronger antioxidant activity. Therefore, the concentrations of rose and garlic, and thyme essential oils were optimized using response surface methodology to obtain the optimal composite ratios, which were 1254 µL/L, 640 µL/L, and 1228 µL/L for rose, garlic, and thyme, respectively. The DPPH free radical-scavenging rate detected using this formulation was 50.2%, basically consistent with the prediction. Zone of inhibition diameters with the compound essential oil, against five spoilage microbes, were all greater than 45 mm. CONCLUSIONS: The essential oil combination had high antimicrobial, against agricultural product spoilage microbes, and antioxidant activities.

Secondary metabolites with fungicide potentials from the deep-sea seamount-derived fungus Talaromyces scorteus AS-242.

Marine natural products play an important role in biopesticides. Seven new secondary metabolites with different structural classes, including two cycloheptapeptides, scortide A (1) and scortide B (2), two 19-nor-diterpenoids, talascortene H (3) and talascortene I (4), two diterpenoid acids, talascortene J (5) and talascortene K (6), and one triterpenoid, talascortene L (7) were isolated and identified from the sea-anemone-derived endozoic fungus Talaromyces scorteus AS-242. Their structures were comprehensively assigned by spectroscopic data analysis, single-crystal X-ray diffraction, tandem mass spectrometry, and electronic circular dichroism (ECD) calculations. The result of the antimicrobial assay demonstrated that compounds 1 - 6 have inhibitory activity against several human, aquatic, and plant pathogens with minimum inhibitory concentration (MIC) values ranging from 1 to 64 µg/mL. Specially, compounds 2 and 4 showed significant activities against the pathogenic fungus Curvularia spicifera with the MIC value of 1 µg/mL, providing an experimental basis of 2 and 4 with the potential as lead compounds to be developed into biopesticides.

Marine Bromotyrosine Derivatives in Spotlight: Bringing Discoveries and Biological Significance.

The Verongida order comprises several sponge families, such as Aplysinellidae, Aplysinidae, Ianthellidae, and Pseudoceratinidae, reported for producing bromotyrosine-derived compounds. First identified in 1913, bromotyrosine derivatives have since captivated interest notably for their antitumor and antimicrobial properties. To date, over 360 bromotyrosine derivatives have been reported. Our review focuses specifically on bromotyrosine derivatives newly reported from 2004 to 2023, by summarizing current knowledge about their chemical diversity and their biological activities.

Synthesis, Antimicrobial Activities, and Molecular Modeling Studies of Agents for the Sortase A Enzyme.

Sortase A (SrtA) is an attractive target for developing new anti-infective drugs that aim to interfere with essential virulence mechanisms, such as adhesion to host cells and biofilm formation. Herein, twenty hydroxy, nitro, bromo, fluoro, and methoxy substituted chalcone compounds were synthesized, antimicrobial activities and molecular modeling strategies against the SrtA enzyme were investigated. The most active compounds were found to be T2, T4, and T19 against Streptococcus mutans (S. mutans) with MIC values of 1.93, 3.8, 3.94 µg/mL, and docking scores of -6.46, -6.63, -6.73 kcal/mol, respectively. Also, these three active compounds showed better activity than the chlorohexidine (CHX) (MIC value: 4.88 µg/mL, docking score: -6.29 kcal/mol) in both in vitro and in silico. Structural stability and binding free energy analysis of S.mutans SrtA with active compounds were measured by molecular dynamic (MD) simulations throughout 100 nanoseconds (ns) time. It was observed that the stability of the critical interactions between these compounds and the target enzyme was preserved. To prove further, in vivo biological evaluation studies could be conducted for the most promising precursor compounds T2, T4, and T19, and it might open new avenues to the discovery of more potent SrtA inhibitors.

Naturally Occurring Polyhydroxylated Spirostanol Saponins, A Review of the Classification, Sources, Biosynthesis, Biological Activities, and Toxicity.

Polyhydroxylated spirostanol saponins, characterized by three or more hydroxy substitutions in the aglycone, have various interesting biological activities. In the present study, "steroids", "saponins", "polyhydroxylated", "spirostanol saponins", and "steroidal saponins" were used as search terms to screen the literature. Cited references were collected between 1950 and 2023 from the Web of Science, SciFinder, and China National Knowledge Internet (CNKI). A total of 407 polyhydroxylated spirostanol saponins were included in this review. These saponins were classified into three types, α, ß, and γ. Polyhydroxylated spirostanol saponins have potential benefits, primarily anti-inflammatory, antimicrobial, cytotoxic, and cAMP phosphodiesterase inhibitory activities. These compounds were found in 11 plant families and 36 genera. The top three families containing the most saponins were Asparagaceae, Melanthiaceae, and Amaryllidaceae, and the top five genera were Trillium, Helleborus, Allium, Dracaena, and Paris. The top five plants were Trillium tschonoskii Maxim., Ypsilandra thibetica Franch., Paris polyphylla var. yunnanensis (Franch.) Hand.-Mazz., Helleborus thibetanus Franch., and Helleborus foetidus L. On the basis of their diverse biological activities, these saponins and related plant resources are worthy of further development and utilization.

Assessment of Vicia faba L. Peels: Phytochemical Characterization and Evaluation of Cytotoxic and Antimicrobial Potentials.

The current study intends to reach the optimal use of plant wastes and explore their biological activities. It evaluated the bioactivities and phytoconstituents of 70% methanol extract of Vicia faba L. peels. The results revealed that the extract possessed very potent cytotoxicity against ovarian cancer cell line (SKOV-3) (IC50 =0.01 µg/mL) which exceeds doxorubicin (IC50 =0.95 µg/ml), a reference anticancer agent, potent cytotoxicity against prostate cancer cell line (PC-3) (IC50 =13.60 µg/ml), and moderate cytotoxicity against liver cancer cell line (HepG2) (IC50 = 40.9 µg/ml). Furthermore, the extract exhibited a potent antimicrobial effect on the tested gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis& Micrococcus luteus) with inhibition zone (IZ) range (14.0 - 23.0 mm), gram-negative bacteria (Pseudomonas aeruginosa) (IZ= 14.0 mm), and pathogenic fungal yeast (Candida albicans) (IZ= 19.0 mm). Moreover, 46 phytoconstituents were tentatively identified using ultra-high-performance liquid chromatography (UHPLC) hyphenated with quadrupole-time-of-flight tandem mass spectrometry (QTOF-MS) in positive ionization mode, 21 phytoconstituents were detected in Vicia faba peel for the first time. High-performance liquid chromatography (HPLC) was used to quantify phenolic compounds, the major compounds were chlorogenic acid, ferulic acid, catechin, and vanillin. In conclusion, plant wastes are a rich source of phytoconstituents that exhibit biological efficacy.

Antimicrobial Isochroman-Derived Atropo-diastereomeric Dimers from Penicillium steckii SCISO 41228.

A pair of unidentified atropisomeric dimers, penicisteckins G (1) and H (2), and twelve known compounds (3-16) were isolated from the marine coral-derived fungus Penicillium steckii SCISO41228. Their structures including the absolute configuration were determined by HR-ESI-MS, ECD, 1D-, and 2D-NMR spectra. Compounds 1 and 2 exhibited potent antibacterial activity against most pathogenic strains, especially for MASA and Micrococcus luteus, with MIC values of 4.0 µg·mL-1. In addition, compounds 2 and 3 exhibit potent antioxidant activity with IC50 values of 10.76 and 8.66 µg·mL-1, respectively.

Two new quinazoline alkaloids produced by Aspergillus versicolor and their antimicrobial activities.

Two new quinazoline alkaloids versicomides G-H (1 and 2), together with seven known compounds, were isolated from Aspergillus versicolor HYQZ-215 obtained from the sediment of Qarhan Salt Lake. Their structures were elucidated by NMR, HRESIMS, and quantum chemical ECD calculations data. The antimicrobial activities of these compounds were evaluated against seven agricultural pathogenic fungi and eight clinically drug-resistant bacteria.

Are phenolic compounds produced during the enzymatic production of prebiotic xylooligosaccharides (XOS) beneficial: a review.

Phenolics produced during xylooligosaccharide production might inhibit xylanases and enhance the antioxidant and antimicrobial activities of XOS. The effects of phenolic compounds on xylanases may depend on the type and concentration of the compound, the plant biomass used, and the enzyme used. Understanding the effects of phenolic compounds on xylanases and their impact on XOS is critical for developing viable bioconversion of lignocellulosic biomass to XOS. Understanding the complex relationship between phenolic compounds and xylanases can lead to the development of strategies that improve the efficiency and cost-effectiveness of XOS manufacturing processes and optimise enzyme performance.

In vitro and In vivo Determination of Biological Activities of Bitter Gourd (Momordica charantia L.) Peel, Flesh and Seeds.

Momordica charantia L. has been remained a well-known medicinal vegetable used traditionally. However, which part is most effective against which disorder, has been remained undiscovered yet. The objective of this study was to examine the antimicrobial, antihyperlipidemic and antihyperglycemic activities of peel, flesh, and seeds of bitter gourd, through in vitro and in vivo assays. Ethanolic extracts from powders of three fractions of bitter gourd were assessed for antimicrobial potential against bacterial and fungal strains, whereas, powders of these fractions were used to determine antihyperlipidemic and antihyperglycemic activity, in alloxan induced diabetic rats. Our results showed that BSE exhibited better antimicrobial activity against Bacillus cereus, whereas BFE exhibited better against Escherichia coli. Blood glucose was significantly lowered by all three powders in a dose dependent manner, when fed to diabetic rats, with the highest decrease by BSP, which reduced the glucose level from 296.20 ± 2.00 mg/dl to 123.10 ± 0.80 mg/dl, at 15 mg dose, after 28 days trial. Elevated levels of TC (101.18 ± 0.65 mg/dl), TG (83.69 ± 0.61 mg/dl) and LDL-C (25.90 ± 0.09 mg/dl) in positive control rats were lowered down in well manners by BSP at 15 mg dose, to 86.30 ± 0.53, 67.70 ± 0.53 and 19.32 ± 0.06 mg/dl, respectively. As compared to BFP and BPP, BSP showed significant involvement in antibacterial, antihyperglycemic, and antihyperlipidemic actions. Along with the edible flesh, peels and seeds, which are usually discarded as waste, could also be utilized for development of pharma foods capable of promoting health.

Carbon Dots: Classically Defined versus Organic Hybrids on Shared Properties, Divergences, and Myths.

Carbon dots are defined as small carbon nanoparticles with effective surface passivation via organic functionalization. The definition is literally a description of what carbon dots are originally found for the functionalized carbon nanoparticles displaying bright and colorful fluorescence emissions, mirroring those from similarly functionalized defects in carbon nanotubes. In literature more popular than classical carbon dots are the diverse variety of dot samples from "one-pot" carbonization of organic precursors. On the two different kinds of samples from the different synthetic approaches, namely, the classical carbon dots versus those from the carbonization method, highlighted in this article are their shared properties and apparent divergences, including also explorations of the relevant sample structural and mechanistic origins for the shared properties and divergences. Echoing the growing evidence and concerns in the carbon dots research community on the major presence of organic molecular dyes/chromophores in carbonization produced dot samples, demonstrated and discussed in this article are some representative cases of dominating spectroscopic interferences due to the organic dye contamination that have led to unfound claims and erroneous conclusions. Mitigation strategies to address the contamination issues, including especially the use of more vigorous processing conditions in the carbonization synthesis, are proposed and justified.

Food matrix design can influence the antimicrobial activity in the food systems: A narrative review.

Antimicrobial agents are safe preservatives having the ability to protect foods from microbial spoilage and extend their shelf life. Many factors, including antimicrobials' chemical features, storage environments, delivery methods, and diffusion in foods, can affect their antimicrobial activities. The physical-chemical characteristics of the food itself play an important role in determining the efficacy of antimicrobial agents in foods; however the mechanisms behind it have not been fully explored. This review provides new insights and comprehensive knowledge regarding the impacts of the food matrix, including the food components and food (micro)structures, on the activities of antimicrobial agents. Studies of the last 10 years regarding the influences of the food structure on the effects of antimicrobial agents against the microorganisms' growth were summarized. The mechanisms underpinning the loss of the antimicrobial agents' activity in foods are proposed. Finally, some strategies/technologies to improve the protection of antimicrobial agents in specific food categories are discussed.

Characterization and identification of antimicrobial compounds from endophytic Fusarium incarnatum isolated from Cymbidium orchids.

This study characterized and identified the antimicrobial compounds from an endophytic fungus (Fusarium incarnatum (C4)) isolated from the orchid, Cymbidium sp. Chromatographic techniques were employed to separate the bioactive compounds from the crude extracts of F. incarnatum (C4). Following bio-guided fractionation, two fractionated extracts (fractions 1 and 2) of F. incarnatum (C4) exhibited antibacterial and antifungal activities against Bacillus cereus (MIC: 0.156 mg/mL) and Ganoderma boninense (MIC: 0.3125 mg/mL), respectively. The active fractions were discovered to comprise of a variety of bioactive compounds with pharmacological importance (alkaloids, flavonoids, phenolic compounds, terpenoids, peptides and fatty acids). Liquid chromatography mass-spectrometry (LCMS) analysis detected the presence of antibacterial (kanzonol N, rifaximin, linoleic acid (d4), cannabisativine, docosanedioic acid, and stearamide) and antifungal components (3-methyl-quinolin-2-ol, prothiocarb, kanzonol N, peganine, 5Z-tridecene, and tetronasin) in fractions 1 and 2, respectively, which may have contributed to the antimicrobial effects. Findings from this study highlighted the important potential of fungal endophytes from medicinal hosts as producers of antimicrobials and antibiotics.

Effectiveness of plant-based hand sanitizer incorporating Quercus infectoria gall extract.

AIMS: Quercus infectoria (Qi), a traditional herbal plant with a broad spectrum of activities on multidrug-resistant bacteria, has been developed for hand sanitizer applications. METHODS AND RESULTS: Antimicrobial activity was evaluated using agar-well diffusion and broth microdilution method. Bactericidal activity was determined following the European Standard 1276 antibacterial suspension test. Neutralization assay was performed to assess antirespiratory syncytial virus. Safety, stability, and skin permeation of Qi hand gel was investigated. Qi hand sanitizer gel inhibited microorganisms ranging from 99.9% to 99.999% against Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant Staph. aureus, Staph. epidermidis, Staph. pseudintermedius, Staph. saprophyticus, Streptococcus pyogenes, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Candida albicans. A significant reduction in main human dermatophytes including Microsporum canis, M. gypseum, and Talaromyces marneffei of ∼50% was observed (P < .05). Qi hand sanitizer gel inactivated >99% viral particles entering human laryngeal epidermoid carcinoma cells in a dose-dependent manner. Scanning electron micrographs further illustrated that Qi hand sanitizer gel disrupted microbial cell membrane after 1-min contact time resulting in cell death. Qi hand sanitizer gel delivered emollient compounds through simulated human skin layers and showed no cytotoxicity on fibroblast cells. Moreover, Qi hand sanitizer gel demonstrated stability under extreme conditions. CONCLUSIONS: Qi hand sanitizer gel was able to inhibit various microorganisms including bacteria, dermatophytes, and virus.

Comparative analysis of antimicrobial compounds from endophytic Buergenerula spartinae from orchid.

A rare fungal endophyte, identified as Buergenerula spartinae (C28), was isolated from the roots of Cymbidium orchids and was characterised and evaluated for its antimicrobial activities. Bio-guided fractionation revealed 4 fractions from B. spartinae (C28) having antibacterial activities against at least one bacterial pathogen tested (Bacillus cereus and Staphylococcus aureus). However, inhibitory activities were absent against pathogenic fungi (Ganoderma boninense, Pythium ultimum and Fusarium solani). Fraction 2 and fraction 4 of B. spartinae (C28) exhibited potent antibacterial activities against S. aureus (MIC: 0.078 mg/mL) and B. cereus (MIC: 0.313 mg/mL), respectively. LCMS analysis revealed the presence of antibacterial agents and antibiotics in fraction 2 (benoxinate, pyropheophorbide A, (-)-ormosanine and N-undecylbenzenesulfonic acid) and fraction 4 (kaempferol 3-p-coumarate, 6-methoxy naphthalene acetic acid, levofuraltadone, hinokitiol glucoside, 3-α(S)-strictosidine, pyropheophorbide A, 5'-hydroxystreptomycin, kanzonol N and 3-butylidene-7-hydroxyphthalide), which may be responsible for the antibacterial activities observed. Most of the bioactive compounds profiled from the antibacterial fractions were discovered for the first time from endophytic isolates (i.e. from B. spartinae (C28)). Buergenerula spartinae (C28) from Cymbidium sp. is therefore, an untapped resource of bioactive compounds for potential applications in healthcare and commercial industries.

A review: Biological activities of novel cyanopyridine derivatives.

The discovery of new therapeutic drugs is heavily reliant on the structural diversity and pharmacological properties of heterocyclic compounds. Pyridine heterocyclic-related medicines, in particular, have garnered considerable attention due to their wide pharmacological activities and therapeutic effects. Among them, cyanopyridine derivatives have demonstrated diverse pharmacological effects. This review aims to systematically compile and discuss the diverse pharmacological effects of cyanopyridine derivatives. The review is divided into multiple sections, highlighting the biological activities of cyanide derivatives, with emphasis on anticancer, antimicrobial (i.e., antibacterial, insecticidal anticonvulsant, and antiviral activities), anticonvulsant, anti-Alzheimer's, and enzyme inhibitory activities. Furthermore, the review emphasizes the interesting therapeutic potential of cyanopyridine derivatives as kinase inhibitors and cytotoxic agents, which are promising candidates for anticancer drug development. The relationship between structure and activity is also discussed, with molecular docking used to provide insights into the mechanism of action of these compounds.

α,ω-Diacyl-Substituted Analogues of Natural and Unnatural Polyamines: Identification of Potent Bactericides That Selectively Target Bacterial Membranes.

In this study, α-ω-disubstituted polyamines exhibit a range of potentially useful biological activities, including antimicrobial and antibiotic potentiation properties. We have prepared an expanded set of diarylbis(thioureido)polyamines that vary in central polyamine core length, identifying analogues with potent methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Acinetobacter baumannii and Candida albicans growth inhibition properties, in addition to the ability to enhance action of doxycycline towards Gram-negative bacterium Pseudomonas aeruginosa. The observation of associated cytotoxicity/hemolytic properties prompted synthesis of an alternative series of diacylpolyamines that explored aromatic head groups of varying lipophilicity. Examples bearing terminal groups each containing two phenyl rings (15a-f, 16a-f) were found to have optimal intrinsic antimicrobial properties, with MRSA being the most susceptible organism. A lack of observed cytotoxicity or hemolytic properties for all but the longest polyamine chain variants identified these as non-toxic Gram-positive antimicrobials worthy of further study. Analogues bearing either one or three aromatic-ring-containing head groups were either generally devoid of antimicrobial properties (one ring) or cytotoxic/hemolytic (three rings), defining a rather narrow range of head group lipophilicity that affords selectivity for Gram-positive bacterial membranes versus mammalian. Analogue 15d is bactericidal and targets the Gram-positive bacterial membrane.