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A Review of Natural Products with Anti-Biofilm Activity
Abstract
Background: Biofilm is a microbial community of microbes that attach to a surface and are enclosed in an extracellular polymeric substance (EPS). Formation of these sessile communities and their inherent resistance to antimicrobial agents are the main reasons for many persistent and chronic infections. Chemotherapy of these infections is unsatisfactory for various reasons including unacceptable toxicity, poor efficacy and drug resistance. In this connection, the last few decades have witnessed wide investigations, which have been geared to investigate the anti-biofilm effects of natural products, including medicinal plant extracts and phytochemicals. Objective: This paper gives a review on the plant extracts and phytochemicals with antibiofilm capability, which hopefully provides useful information and guidance for future antimicrobial study. Method: This review is to summarize the natural products, including various phytochemicals, decoctions, plant fractions and extracts that have shown anti-biofilm activity. Literatures were collected from published articles that reported in vitro or in vivo anti-biofilm activity of natural products. Results: A total of 95 related references were found. The phytochemicals, fractions and extracts are grouped by their general classes or by their putative active components. More than 90 bioactive anti-biofilm compounds have been identified from different parts of the plants. The inhibitory concentration of the natural products was also included, and some of them were investigated for their possible anti-biofilm mechanism. Conclusion: This review has demonstrated solid evidences that plants are an excellent source to provide abundant natural compounds for the development of preventative and therapeutic agents against biofilm-based infections.
... Biofilms are an adherent population of sessile bacteria that stick to a live or inactive surface because they are enclosed in an extracellular polymeric substance (EPS) matrix (Lahiri et al., 2019). Numerous bacteria and an extracellular matrix consisting of proteins, lipids, nucleic acids, polysaccharides, and other biological or chemical materials make up its main components (Song et al., 2018). On a wide range of biotic and abiotic surfaces, these biofilms can form, including on medicinal supplies and foliage from plants. ...
... Plants communicate with one another via these secondary metabolites. Numerous plant chemicals have demonstrated antibiofilm characteristics and have been shown to greatly limit the formation of biofilms (Song et al., 2018). ...
... Numerous academic studies have emphasized the ability of phytochemicals found in a variety of plants and plant extracts to both prevent the growth of new biofilm and break down preexisting biofilm (Song et al., 2018). Many species of Erigeron yield essential oils that are rich in terpenoids and physiologically active polyacetylene compounds. ...
An adhering population of sessile bacteria enclosed in an extracellular polymeric material (EPS) is called a biofilm. One important aspect of the pathogenicity of many bacteria that cause chronic illnesses is the production of biofilms. Many plants have been shown to possess antibacterial qualities and are utilized in the treatment of various infectious diseases. The purpose of this work is to examine the phytochemicals, antibacterial, and antibiofilm properties of the leaves of Erigeron bonariensis (L.) Cronq. methanolic extract. Standard biochemical procedures were used to conduct a preliminary phytochemical study. To determine which functional groups were present in the phytochemicals, FTIR analysis was performed. While MIC was ascertained by the Resazurin method, the well diffusion method was utilized to evaluate the antibacterial activity. DPPH and the hydrogen peroxide techniques were used to assess the antioxidant capabilities. An experiment for biofilm inhibition was run against the test organisms (Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecalis). There are secondary metabolites in the methanolic extract of E. bonariensis that are associated with different functional groups. Significant antibacterial, antibiofilm, and antioxidant properties were also demonstrated by E. bonariensis leaf extract. According to our research, E. bonariensis shows promise as a therapeutic candidate for the management of infectious diseases, especially those brought on by biofilm.
... As a result, the treatment of biofilmassociated infections is a notorious challenge due to the difficulty of diagnosis and the lack of appropriate biomarkers (Floyd et al., 2017). Therefore, new strategies to prevent or eradicate bacterial biofilms have been studied extensively (Alara et al., 2021;Lu et al., 2019;Song et al., 2018). In recent years, medicinal plants have received attention for their biological properties, including antioxidant and anti-inflammatory (Unuofin & Lebelo, 2020), anticancer (Mani et al., 2021), antimicrobial and antibiofilm formation (Ribeiro et al., 2019). ...
Klebsiella pneumoniae is an opportunistic pathogen related to several cases of healthcare-associated and community-acquired infections worldwide, especially in Brazil. Numerous studies have shown that isolated secondary metabolites, such as phenolic acids, have the potential to act against this problem. This study aimed to investigate the inhibitory potential associated with phenolic acids on growth and biofilm formation in clinical isolates of Multidrug-Resistant and Extensively Drug-Resistant K. pneumoniae (MDR/XDR-KP). Four clinical isolates from a public hospital in Recife, Pernambuco, Brazil, and a sensitive standard strain were used. The initial identification of the samples was carried out using VITEK®2 and BD-PhoenixTM 100 automation equipment, as well as the characterization of the resistance profile. The samples were then confirmed using the MALDI-TOF/MS technique. The Crystal Violet method was used to assess biofilm formation capacity. Four phenolic acids (gallic, trans-ferulic, caffeic, and 4-hydroxybenzoic) were used to evaluate the antimicrobial and biofilm-forming activities. The isolates were confirmed as K. pneumoniae species with MALDI-TOF/MS scores ranging from 2.459-2.083. The samples showed both MDR and XDR resistance profiles, and biofilm formation with different intensities. Of all the compounds tested, caffeic and trans-ferulic acids were the most effective, with growth and biofilm inhibition values of 70-85% and 70-90% using a concentration of 2 mg/mL, respectively. Notably, K. pneumoniae belongs to a group considered by the WHO to be a critical public health priority to be combated. In this context, the results showed that phenolic acids had a great potential impact on both bacterial growth and the biofilm-forming capacity of MDR/XDR-KP clinical isolates. This leads us to recognize the use of phenolic acids as a possible alternative in the fight against infections caused by MDR, XDR, and biofilm-forming bacterial species.
... Numerous studies have looked at natural resources to understand how to prevent and control biofilms 8 . Humans have traditionally exploited natural compounds and food's secondary metabolites, medicine, and cosmetics 4 . ...
Most infectious diseases are primarily caused by the growth of microorganisms called biofilms. The formation of
bacterial biofilms enables microorganisms to inhabit biotic and abiotic surfaces which increases their resistance to
antimicrobials. To control this issue, there is a critical need for novel approaches and compounds can suppress the
expression or regulation of virulence genes. A potential method for disarming rather than eliminating bacterial pathogens
is antivirulence therapy based on the blockage of biofilm pathways. In current study, the action of water, diethyl ether
and acetone extraction on two types of algae namely Scenedesmus quadricauda and Chlorosarcinopsis eremi in their subinhibitory concentration (SIC) was investigated against Pseudomonas aeroginosa and Escherichia coli biofilm formation
and their gene expression instead of killing them. The SIC values of each extract were determined by minimal inhibitory
concentration (MIC) assay then gene expression products were assessed using Real-Time PCR (RT-PCR) when the cells
were exposed to the SICs of algal extracts. Results revealed that the expression of ndvB (P. aeroginosa) & FimH (E. coli)
genes that involved in biofilm formation was reduced by the extracts at their SICs. Diethyl ether was the best solvent
with greater inhibitory activity followed by water and acetone against two pathogenic bacteria under this survey. Values
of 25 mg/ml, 20 mg/ml for MIC and 15 mg/ml, 10 mg/ml for SIC were recorded by diethyl ether solvent against
P. aeroginosa and E. coli respectively. According to biofilm detection, water extract was more efficient in S. quadricauda
against P. aeroginosa and E. coli.
... The ability of the aqueous E. senegalensis extract to inhibit biofilm formation in K. pneumoniae suggests it may be a useful tool for reducing microbial colonization on surfaces and mucosal epithelia, potentially preventing serious infections [74]. The antibiofilm activity against K. pneumoniae is thought to be due to the extraction solvent and the presence of bioactive compounds such as phenolics, flavonoids, quinones, alkaloids, terpenoids, reducing sugars, and cardiac glycosides, which may inhibit quorum sensing and biofilm production [75][76][77]. It is noted that plant extracts have bioactive compounds with the following antibiofilm activity such as enzymatic or chemical properties which can degrade extracellular polymeric substance (EPS) of biofilm [78,79], interference with bacterial communication strategies (quorum sensing) [80], bacterial adhesion proteins preventing initial adherence to surfaces [81], direct killing of bacterial within the biofilm matrix [82][83][84], inhibit efflux pump (which is the main mechanism of resistance in biofilm formation) and thereby reducing biofilm production. ...
Biofilms are bacterial communities on surfaces within an extracellular matrix. Targeting biofilm-specific bacteria is crucial, and natural compounds with reported antibiofilm activity have garnered significant interest. The study evaluated the antibacterial and antibiofilm activity of Erythrina senegalensis leaf extract against multidrug-resistant (MDR) Gram-negative bacteria, including S. Typhimurium, S. Typhi, S. Enteritidis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The leaf extract was prepared using aqueous and ethanol solvents, and qualitative phytochemical screening revealed the presence of various bioactive compounds such as tannins, saponins, cardiac glycosides, flavonoids, terpenoids, alkaloids, anthraquinone, reducing sugar, and ketones. A Kirby–Bauer disc diffusion assay was performed to test the susceptibility of antibiotics, and the antibacterial efficacy of the aqueous and ethanol extracts of E. senegalensis was determined using the cup-plate method, while the antibiofilm activities were determined using the crystal violet titer-plate method. The aqueous and ethanol extracts of E. senegalensis revealed the presence of tannins, saponins, cardiac glycosides, flavonoids, terpenoids, alkaloids, anthraquinone, reducing sugar, and ketones. The study found that the Gram-negative bacteria isolates that were MDR were S. Typhimurium, S. Enteritidis, and P. aeruginosa, while K. pneumoniae was resistant to beta-lactam and fluoroquinolones, and S. Typhi was susceptible to all antibiotics tested. Statistically, susceptibility to antibiotics had an inverse, weak, and significant relationship with biofilm production (r = −0.453, −0.106, −0.124, −0.106, −0.018, n = 10, p < 0.05). The aqueous extract showed good biofilm inhibition against K. pneumoniae and P. aeruginosa, and poor biofilm inhibition against S. Enteritidis, while S. Typhimurium and S. Typhi exhibited no biofilm inhibition. The ethanol extract did not demonstrate any antibiofilm activity against the tested Gram-negative pathogens. The study suggests that the Gram-negative bacteria’s capacity to form biofilms is negatively associated with their antibiotic resistance phenotypes, and the aqueous extract of E. senegalensis exhibited moderate antibiofilm activity against K. pneumoniae, P. aeruginosa, and S. Enteritidis.
... In addition, the catechin bioactive compound can reduce 72% of P. aeruginosa biofilms' extracellular DNA content, an essential structural component of bacterial biofilm formation. Similarly, Song et al. (2018) found that negletein flavone, isolated from the leave extract of Scutellaria oblonga, exhibited a 72.3% P. aeruginosa biofilmreducing ability at a concentration of 64 μg/mL. These findings underscore the potential application of plant extracts as antibacterial agents against biofilms, highlighting the role of bioactive constituents, such as flavonoids and other phenolic compounds, in minimizing bacterial adherence, which is the initial step in bacterial biofilm formation. ...
Commonly used antimicrobial agents are no longer effective due to their overuse or misuse. In addition, many medicinal plant extracts can combat infectious diseases due to their main active constituents or secondary metabolites. The current study aimed to assess the bioactivities of Launaea nudicaulis (LN) leaf extract (LE) against different multi-drug resistant (MDR) Pseudomonas aeruginosa (P. aeruginosa) isolates. The ethyl acetate extract of a Launaea nudicaulis (LN) leaf was analyzed using GC–MS, which identified 27 key bioactive compounds. The major constituents found were as follows: 7-acetyl-6-ethyl-1,1,4,4-tetramethyltetralin, isopropyl myristate, thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl-2-butenyl ester, hahnfett, cyclopentane acetic acid, 3-oxo-2-pentyl-, methyl ester, hexadecanoic acid, and dotriacontane. Our study demonstrated that the LN leaf was a rich source of other important phytochemicals, including phenolic acids, tannins, saponins, and steroids. The relative biosafety of the L. nudicaulis LE was determined from the elevated inhibitory concentration 50 (IC50) of 262 μg/mL, as calculated from the cytotoxicity assay against the Wi-38 normal cell line. Conversely, 12.7 and 24.5 μg/mL were the recorded low IC50 values for the tested extract against the MCF-7 and Hep-G2 cancerous cell lines, respectively, reflecting its potent activity against the tested cancerous cell lines. Microbiologically, the susceptible P. aeruginosa isolates to the tested extract showed a growth inhibition zone diameter, in the well diffusion assay, ranging from 11.34 ± 0.47 to 26.67 ± 0.47 mm, and a percent inhibition (PI) value of 50–106.2%, reflecting its acceptable activity. In addition, the broth microdilution assay recorded minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in the ranges of 15.625–1,000 μg/mL and 125–1,000 μg/mL, respectively. In conclusion, the L. nudicaulis LE revealed showed promising activity and high selectivity against P. aeruginosa. Moreover, the extract exhibited natural anticancer activities with safe low concentrations, indicating its potential as a superior candidate for future studies of its active constituents.
... However, the constant evolution of resistant bugs suggests newer innovative attempts to counteract bacterial infections. Thus, scientists are more than ever focusing on the discovery of agents that can affect biofilms (Song et al., 2018). Morbidity and mortality by S. aureus and P. aeruginosa are the most common causes of death worldwide. ...
Eryngium aquaticum L. (Apiaceae), a culinary herb enjoyed in global cuisines, is also valued for its medicinal properties. The essential oil (EO) extracted from E. aquaticum leaves by hydro-distillation was subjected to antibacterial and antibiofilm activity using a microtiter plate-based in vitro assay against Staphylococcus aureus and Pseudomonas aeruginosa. Compounds identified by GC-MS analysis of EO were screened against the transcriptional regulatory proteins SarA of S. aureus and LasR of P. aeruginosa by molecular docking analysis. The minimum inhibitory concentration (MIC) was recorded as 250 μg/mL against both of these two pathogens. The EO of E. aquaticum also showed concentration-dependent antibiofilm activity against these pathogens, with a maximum inhibition of 50.9 and 48.03% against P. aeruginosa and S. aureus, respectively, at the highest concentration (500 μg/mL) tested. The GC-MS analysis identified 17 compounds and all of them showed moderate to weak binding affinity for the active sites of SarA and LasR, with pentanedioic acid (2,4-di-t-butylphenyl) mono-ester showing the best docking score against SarA (-5.7 kcal/mol) and LasR (-8.0 kcal/mol). This study suggests that E. aquaticum can be a good source of EO with antibacterial and antibiofilm activity against P. aeruginosa and S. aureus.
Peronema canescens Jack has shown promising anticancer activities. This study set out to investigate the rich biodiversity and potential anticancer properties of fungal endophytes derived from P. canescens. Forty‐eight pure isolates of fungal endophytes were obtained from cultures of both young and old leaves across eleven different branch types. Furthermore, four specific fungal strains were selected for the evaluation of anticancer activity: Fusarium sp. strain PCL‐34‐B, Phomopsis sp. strain PCL‐Y‐48, Lasiodiplodia sp. strain PCL‐O‐9, and Phomopsis sp. strain PCL‐O‐23. The ethyl acetate and methanol extracts of these fungal endophytes demonstrated intriguing results, with the ethyl acetate extracts of PCL‐Y‐48 exhibiting the most significant cytotoxic activity among the various fungal endophyte extracts. The IC50 values were recorded at 10.52 and 33.54 mg/L against the A549 lung cancer and MG‐63 osteosarcoma cells, respectively. The identification of chemical substances reveals a range of components believed to play a role in their anticancer effects.
A shape-adaptive hydrogel with sequential antibacterial and osteogenic functions was proposed to repair irregular osteoporosis bone defects. Naringin was incorporated into microspheres and dispersed into GelMA to repair mandibular defects in rats and alveolar bone defects in osteoporotic rats.
The emergence of non-albicans Candida as a potential causative agent of candidiasis
following Candida albicans is occurring globally. It is known that phenolic cresols,
thymol, and carvacrol have anti-Candida characteristics. However, there are few papers
that disclose the mechanism of action, which is characterized by a damaged cell wall
and ergosterol synthesis, as well as calcium-induced death in C. albicans. This work
utilized in-silico docking analysis to examine the molecular targets of thymol and car
vacrol in Candida glabrata. The results were then validated in vitro by antifungal sus
ceptibility testing and growth curve analysis. The study incorporated C. glabrata dele
tion mutants for the target proteins to gain understanding of the function of these pro
teins in the antifungal effects of the two monoterpenoids. After conducting molecular
docking and in silico toxicity evaluations, thymol and carvacrol were chosen for in
vitro investigations. Experimental tests conducted in a laboratory setting have shown
that both phytocompounds exhibit strong binding affinity towards cell wall synthesis
proteins (Kre1p, Kre2p, Ecm33p), calcium channel proteins (Mid1p, Ecm7p), and pro
teins involved in the ergosterol synthesis pathway (Erg5p). These proteins are likely to
be the specific targets for the anti-Candida properties of the two isomeric monoterpe
noids in C. glabrata. Minimum inhibitory concentration (MIC50) values for thymol and
carvacrol range from 50 µg/ml to 75 µg/ml. The wild-type strains exhibit a minimum
fungicidal concentration of 100 µg/ml for thymol and 125 µg/ml for carvacrol. The
results underscore the significance of these proteins in the fungal reaction to thymol
and carvacrol and also indicate a promising opportunity for the development of novel
antifungal treatment methods utilizing these proteins.
BACKGROUND:
The frequent occurrences of antibiotic-resistant biofilm forming pathogens have become global issue since various measures that had been taken to curb the situation led to failure. Euphorbia hirta, is a well-known ethnomedicinal plant of Malaysia with diverse biological activities. This plant has been used widely in traditional medicine for the treatment of gastrointestinal, bronchial and respiratory ailments caused by infectious agents.
METHODS:
In the present study, chemical compositions of methanol extract of E. hirta L. aerial part was analyzed by gas chromatography and gas chromatography coupled to mass spectrometry. A relevant in vitro model was developed to assess the potency of the E. hirta extract to inhibit the bacterial biofilm formation as well as to eradicate the established biofilms. Besides biofilm, E. hirta extract was also evaluated for the inhibition efficacy on planktonic cells using tetrazolium microplate assay. For these purposes, a panel of clinically resistant pathogens and American type culture collection (ATCC) strains were used.
RESULTS:
The methanolic extract of aerial part of E. hirta was predominantly composed of terpenoid (60.5%) which is often regarded as an active entity accountable for the membrane destruction and biofilm cell detachment. The highest antibacterial effect of crude E. hirta extract was observed in the clinical isolates of Pseudomonas aeruginosa with minimum inhibitory concentration (MIC) value of 0.062 mg/ml. The extract also displayed potent biofilm inhibition and eradication activity against P. aeruginosa with minimum biofilm inhibition concentration (MBIC) and minimum biofilm eradication concentration (MBEC) values of 0.25 mg/ml and 0.5 mg/ml, respectively.
CONCLUSIONS:
The crude methanol extract of E. hirta has proven to have interesting and potential anti-biofilm properties. The findings from this study will also help to establish a very promising anti-infective phytotherapeutical to be exploited in the pharmaceutical industries.
The exopolysaccharides (EPS) produced by Streptococcus mutans-derived glucosyltransferases (Gtfs) are essential virulence factors associated with the initiation of cariogenic biofilms. EPS forms the core of the biofilm matrix-scaffold, providing mechanical stability while facilitating the creation of localized acidic microenvironments. Cranberry flavonoids, such as A-type proanthocyanidins (PACs) and myricetin, have been shown to inhibit the activity of Gtfs and EPS-mediated bacterial adhesion without killing the organisms. Here, we investigated whether a combination of cranberry flavonoids disrupts EPS accumulation and S. mutans survival using a mixed-species biofilm model under cariogenic conditions. We also assessed the impact of cranberry flavonoids on mechanical stability and the in situ pH at the biofilm-apatite interface. Topical application of an optimized combination of PACs oligomers (100-300 μM) with myricetin (2 mM) twice daily was used to simulate treatment regimen experienced clinically. Treatments with cranberry flavonoids effectively reduced the insoluble EPS content (>80% reduction vs. vehicle-control; p
Scutellaria oblonga Benth., a hitherto phytochemically unexplored Indian medicinal folklore plant was extracted with acetone and subjected to chromatography to yield nine flavonoids, for the first time from this plant. Antimicrobial assays were performed against 11 foodborne pathogens, and three molecules (Techtochrysin, Negletein and Quercitin-3-glucoside) depicted significant activity. These molecules were assessed for their rate of antibacterial action using time-kill curves which depicted complete inhibition of most of the bacteria within 12-16 h. The significant biofilm-reducing capability exhibited by these three molecules formed a significant finding of the current study. In most of the experiments, a 90-95% reduction in biofilms was observed. Thus, flavonoids as natural molecules from S. oblonga could be further researched to be used as potent antimicrobial and antibiofilm agents.
Wild mushrooms are mainly collected during the rainy season and valued as a nutritious food and sources of natural medicines and nutraceuticals. The aim of this study was to determine the chemical composition and bioactive properties (antioxidant, antimicrobial and cytotoxicity) of Polyporus squamosus from two different origins, Portugal and Serbia. The sample from Portugal showed higher contents of as protein (17.14 g/100 g), fat (2.69 g/100 g), ash (3.15 g/100 g) and carbohydrates (77.02 g/100 g); the same sample gave the highest antioxidant activity: highest reducing power, DPPH radical scavenging activity, and lipid peroxidation inhibition in both β-carotene/linoleate and TBARS assay. These results could be related to its higher content in total tocopherols (1968.65 μg/100 g) and phenolic compounds (1.29 mg/100 g). Both extracts exhibited antibacterial activity against all the tested organisms. The samples from Serbia gave higher overall antibacterial activity and showed excellent antibiofilm activity (88.30 %). Overall, P. squamosus methanolic extracts possessed antioxidant, antimicrobial, antibiofilm and anti-quorum sensing activity, and without toxicity for liver cells. This investigation highlights alternatives to be explored for the treatment of bacterial infections, in particular against Pseudomonas aeruginosa. This study provides important results for the chemical and bioactive properties, especially antimicrobial activity of the mushroom P. squamosus. Moreover, to the authors’ knowledge this is the first report on sugars, organic acids, and individual phenolic compounds in P. squamosus.
Four new polyol polyketides containing a decalin ring, nahuoic acids B-E (1-4), together with a known analogue, nahuoic acid A (5), possessing an unprecedented carbon skeleton, were isolated from a culture broth of the marine-derived Streptomyces sp. SCSGAA 0027. Their structures were determined by detailed analysis of spectroscopic data and chemical transformations including acetonide formation and Mosher's ester method. Compounds 1-5 showed weak antibiofilm activity against Shewanella onedensis MR-1 biofilm. This is the first series of analogues of the novel selective SETD8 inhibitor nahuoic acid A.
A dichloromethane extract of the roots from the Panamanian plant Swartzia simplex exhibited a strong antifungal activity in a bioautography assay against a genetically modified hypersusceptible strain of Candida albicans. At-line HPLC activity based profiling of the crude extract enabled a precise localization of the antifungal compounds, and dereplication by UHPLC-HRESIMS indicated the presence of potentially new metabolites. Transposition of the HPLC reversed-phase analytical conditions to medium-pressure liquid chromatography (MPLC) allowed an efficient isolation of the major constituents. Minor compounds of interest were isolated from the MPLC fractions using semipreparative HPLC. Using this strategy, 14 diterpenes (1-14) were isolated, with seven (5-10, 14) being new antifungal natural products. The new structures were elucidated using NMR spectroscopy and HRESIMS analysis. The absolute configurations of some of the compounds were elucidated by electronic circular dichroism spectroscopy. The antifungal properties of these compounds were evaluated as their minimum inhibitory concentrations in a dilution assay against both hypersusceptible and wild-type strains of C. albicans and by assessment of their antibiofilm activities. The potential cytological effects on the ultrastructure of C. albicans of the antifungal compounds isolated were evaluated on thin sections by transmission electron microscopy.
Bacteria that adhere to implanted medical devices or damaged tissue can encase themselves in a hydrated matrix of polysaccharide and protein, and form a slimy layer known as a biofilm. Antibiotic resistance of bacteria in the biofilm mode of growth contributes to the chronicity of infections such as those associated with implanted medical devices. The mechanisms of resistance in biofilms are different from the now familiar plasmids, transposons, and mutations that confer innate resistance to individual bacterial cells. In biofilms, resistance seems to depend on multicellular strategies. We summarise the features of biofilm infections, review emerging mechanisms of resistance, and discuss potential therapies.
Twenty compounds were detected in the essential oil of Rhanterium suaveolens representing 98.01% of the total oil content. Perillaldehyde (45.79%), caryophyllene oxide (24.82%) and β-cadinol (5.61%) were identified as the main constituents. In β-carotene-linoleic acid assay, both the oil and the methanol extract exhibited good lipid peroxidation inhibition activity, with IC50 values of 17.97 ± 5.40 and 11.55 ± 3.39 μg/mL, respectively. In DPPH and CUPRAC assays, however, the methanol extract exhibited a good antioxidant activity. The highest antibiofilm activity has been found 50.30% against Staphylococcus epidermidis (MU 30) at 20 μg/mL for essential oil and 58.34% against Micrococcus luteus (NRRL B-4375) at 25 mg/mL concentration for methanol extract. The in vitro anticholinesterase activity of methanol extract showed a moderate acetylcholinesterase inhibitory (IC50 = 168.76 ± 0.62 μg/mL) and good butyrylcholinesterase inhibitory (IC50 = 54.79 ± 1.89 μg/mL) activities. The essential oil was inactive against both enzymes.
Pandanus amaryllifolius Roxb. (Pandanaceae) is used as a flavor and in folk medicine in Southeast Asia. The ethanolic crude extract of the aerial parts of P. amaryllifolius exhibited antioxidant, antibiofilm, and anti-inflammatory activities in previous studies. In the current investigation, the purification of the ethanolic extract yielded nine new compounds, including N-acetylnorpandamarilactonines A (1) and B (2); pandalizines A (3) and B (4); pandanmenyamine (5); pandamarilactones 2 (6) and 3 (7), and 5(E)-pandamarilactonine-32 (8); and pandalactonine (9). The isolated alkaloids, with either a γ-alkylidene-α,β-unsaturated-γ-lactone or γ-alkylidene-α,β-unsaturated-γ-lactam system, can be classified into five skeletons including norpandamarilactonine, indolizinone, pandanamine, pandamarilactone, and pandamarilactonine. A plausible biosynthetic route toward 1-5, 7, and 9 is proposed.