Non-Volatile Component and Antioxidant Activity: A Comparative Analysis between Litsea cubeba Branches and Leaves

Litsea cubeba, which is found widely distributed across the Asian region, functions as both an economic tree and a medicinal plant with a rich historical background. Previous investigations into its chemical composition and biological activity have predominantly centered on volatile components, leaving the study of non-volatile components relatively unexplored. In this study, we employed UPLC-HRMS technology to analyze the non-volatile components of L. cubeba branches and leaves, which successfully resulted in identifying 72 constituents. Comparative analysis between branches and leaves unveiled alkaloids, organic acids, and flavonoids as the major components. However, noteworthy differences in the distribution of these components between branches and leaves were observed, with only eight shared constituents, indicating substantial chemical variations in different parts of L. cubeba. Particularly, 24 compounds were identified for the first time from this plant. The assessment of antioxidant activity using four methods (ABTS, DPPH, FRAP, and CUPRAC) demonstrated remarkable antioxidant capabilities in both branches and leaves, with slightly higher efficacy observed in branches. This suggests that L. cubeba may act as a potential natural antioxidant with applications in health and therapeutic interventions. In conclusion, the chemical composition and antioxidant activity of L. cubeba provides a scientific foundation for its development and utilization in medicine and health products, offering promising avenues for the rational exploitation of L. cubeba resources in the future.

Therapeutic potential of Litsea cubeba essential oil in modulating inflammation and the gut microbiome

Inflammation, a sophisticated and delicately balanced physiological mechanism, is paramount to the host's immunological defense against pathogens. However, unfettered and excessive inflammation can be instrumental in engendering a plethora of chronic ailments and detrimental health repercussions, notably within the gastrointestinal tract. Lipopolysaccharides (LPS) from bacteria are potent endotoxins capable of instigating intestinal inflammation through the disruption of the intestinal epithelial barrier and the stimulation of a pro-inflammatory immune response. In this study, we sought to investigate the influence of Litsea cubeba essential oil (LCEO) on LPS-induced intestinal inflammation and associated changes in the gut microbiota. We investigated the therapeutic potential of LCEO for gut health, with particular emphasis on its gut protective properties, anti-inflammatory properties and modulation of the gut microbiome. LCEO exhibited protective effects on colonic tissue by protecting crypts and maintaining epithelial integrity, and anti-inflammatory properties by reducing TNF-α, IL-6, and IL-1β levels in the liver and intestine. Citral, a major component of LCEO, showed robust binding to IL-1β, IL-6, and TNF-α, exerting anti-inflammatory effects through hydrogen bonding interactions. Using community barplot and LEfSe analyses, we detected significant variation in microbial composition, identified discrete biomarkers, and highlighted the influence of essential oils on gut microbial communities. Our research suggests that LCEO may be a promising natural compound for ameliorating diarrhea and intestinal inflammation, with potential implications for modulating the gut microbiome. These observations provide invaluable insight into the potential therapeutic role of LCEO as a natural anti-inflammatory agent for treating intestinal inflammatory disorders, particularly in the setting of a dysregulated immune response and altered gut microbiota. Furthermore, our findings highlight the need to understand the complex interplay between the host, the gut microbiome and natural products in the context of inflammatory diseases.

Dietary Litsea cubeba essential oil supplementation improves growth performance and intestinal health of weaned piglets

This paper was to determine the effects of dietary Litsea cubeba essential oil (LEO) supplementation on growth performance, immune function, antioxidant level, intestinal morphology and microbial composition in weaned piglets. One hundred and ninety-two piglets (Duroc × [Large White × Landrace]) with 6.85 ± 0.22 kg mean body weight weaned at 21 d of age were randomly assigned to 4 treatment groups with 8 replicates and were fed with a basal diet (CON) or CON diet containing 100 (LLEO), 200 (MLEO) and 400 (HLEO) mg/kg LEO. The results revealed that HLEO supplementation (P < 0.05) increased the average daily gain on d 28 compared with CON. MLEO and HLEO supplementation decreased (P < 0.05) feed conversion ratio. LEO-containing diets had a lower (P < 0.05) diarrhea rate. Supplementation with HLEO increased (P < 0.05) total antioxidant capacity (T-AOC) both in the serum and liver. Meanwhile, the supplementation of MLEO and HLEO resulted in higher (P < 0.05) glutathione peroxidase (GPx) activities both in serum and liver. Supplementation of HLEO increased (P < 0.05) serum immunoglobulin A, immunoglobulin G and interleukin-10, whereas supplementation with MLEO and HLEO decreased (P < 0.05) tumor necrosis factor-α. Villus height in the duodenum or jejunum was increased (P < 0.05) in the HLEO group, and the villus height to crypt depth ratio in the jejunum was also improved (P < 0.05) in the MLEO group. The addition of LEO increased (P < 0.05) the richness and diversity of the microbial community in the cecum, which mainly increased the relative abundance of Oscillospiraceae _UCG-005, Faecalibacterium, Blautia and Coprococcus. Piglets supplemented with HLEO increased (P < 0.05) the concentration of short chain fatty acids (SCFA), including acetic acid in the cecum and propionic acid in the colon. In conclusion, these findings indicated that LEO supplementation improved growth performance and intestinal health in weaned piglets.

LcWRKY17, a WRKY Transcription Factor from Litsea cubeba, Effectively Promotes Monoterpene Synthesis

The WRKY gene family is one of the most significant transcription factor (TF) families in higher plants and participates in many secondary metabolic processes in plants. Litsea cubeba (Lour.) Person is an important woody oil plant that is high in terpenoids. However, no studies have been conducted to investigate the WRKY TFs that regulate the synthesis of terpene in L. cubeba. This paper provides a comprehensive genomic analysis of the LcWRKYs. In the L. cubeba genome, 64 LcWRKY genes were discovered. According to a comparative phylogenetic study with Arabidopsis thaliana, these L. cubeba WRKYs were divided into three groups. Some LcWRKY genes may have arisen from gene duplication, but the majority of LcWRKY evolution has been driven by segmental duplication events. Based on transcriptome data, a consistent expression pattern of LcWRKY17 and terpene synthase LcTPS42 was found at different stages of L. cubeba fruit development. Furthermore, the function of LcWRKY17 was verified by subcellular localization and transient overexpression, and overexpression of LcWRKY17 promotes monoterpene synthesis. Meanwhile, dual-Luciferase and yeast one-hybrid (Y1H) experiments showed that the LcWRKY17 transcription factor binds to W-box motifs of LcTPS42 and enhances its transcription. In conclusion, this research provided a fundamental framework for future functional analysis of the WRKY gene families, as well as breeding improvement and the regulation of secondary metabolism in L. cubeba.

LcERF134 increases the production of monoterpenes by activating the terpene biosynthesis pathway in Litsea cubeba

Litsea cubeba, an aromatic species of the Lauraceae family, produces a diverse array of monoterpenes. The biosynthesis of monoterpenes is regulated by transcriptional factors (TFs), such as APETALA2/ethylene response factor (AP2/ERF). However, the regulatory mechanisms that control the AP2/ERF gene responsible for the biosynthesis of monoterpenes in L. cubeba have yet to be elucidated. Here, we identified an AP2/ERF gene, LcERF134, as an activator for the accumulation of citral and other monoterpenes. The expression level of LcERF134 was consistent with terpene synthase LcTPS42 in the pericarp. The transient overexpression of LcERF134 significantly increased monoterpene production in L. cubeba as well as the expression of rate-limiting genes involved in the monoterpene biosynthesis pathway. Furthermore, yeast one-hybrid, dual-luciferase and electrophoretic mobility shift assays demonstrated that LcERF134 activated the monoterpene biosynthesis pathway by directly binding to the GCC-box elements of the LcTPS42 and LcGPPS.SSU1 promoters. However, the overexpression of LcERF134 in tomatoes had no impact on the synthesis of monoterpenes, thus indicating that LcERF134 is a species-specific TF. Our research demonstrated that LcERF134 significantly increased the biosynthesis of monoterpenes by inducing the expression of LcTPS42 and LcGPPS.SSU1, thus offering insight into how to enhance the flavor of L. cubeba essential oil.

First report of black patch disease caused by Phyllosticta capitalensis on Litsea cubeba in China

Litsea cubeba, an economical important tree species originally from China, produces fruit from which essential oils are extracted and extensively used in the chemical industry (Zhang et al. 2020). In August 2021, a large-scale outbreak of black patch disease was first observed on the leaves of Litsea cubeba in Huaihua (27°33'N; 109°57'E), Hunan province, China (disease incidence 78%). A second outbreak in 2022, in the same area, lasted from June to August. Symptoms consisted of irregular lesions that initially appeared as small black patches near the lateral veins. These lesions grew along the lateral veins and formed feathery patches until almost the entire lateral veins of the leaves were infected by the pathogen. The infected plants grew poorly and eventually the leaves desiccated and the tree defoliated. To identify the causal agent, the pathogen was isolated from nine symptomatic leaves from three trees. Symptomatic leaves were washed with distilled water three times. Leaves were cut into small pieces (11 cm), surface sterilized with 75% ethanol for 10s and 0.1% HgCl2 for 3 min, and then washed 3 times in sterile distilled water. Surface disinfected leaf pieces were placed onto potato dextrose agar (PDA) medium with cephalothin (0.2 mg/ml) and incubated at 28°C for 4-8 days (about 16h light, 8h dark). Seven morphologically identical isolates were obtained, from which five were selected for further morphological examination and three for molecular identification and pathogenicity test. Strains from grayish white colonies with a granular surface and grayish black wavy edges; bottom of the colonies turned black over time. Conidia were hyaline and nearly elliptical, unicellular. The sizes of conidia ranged from 8.59 to 15.06 μm (n=50) in length and 3.57 to 6.36 μm (n=50) in width. These morphological characteristics are consistent with the description of Phyllosticta capitalensis (Guarnaccia et al. 2017, Wikee et al. 2013). To further confirm the identity of this pathogen, genomic DNA of three isolates (phy1, phy2 and phy3) were extracted to amplify the internal transcribed spacer (ITS) region, the 18S rDNA region, the transcription elongation factor (TEF), and actin (ACT) gene with ITS1/ITS4 (Cheng et al. 2019), NS1/NS8 (Zhan et al. 2014), EF1-728F/EF1-986R (Druzhinina et al. 2005) and ACT-512F/ACT-783R (Wikee et al. 2013) primers, respectively. Sequence similarity indicated that these isolates were highly homologous to Phyllosticta capitalensis. The ITS (Genbank No. OP863032, ON714650 and OP863033), 18S rDNA (Genbank No. OP863038, ON778575 and OP863039), TEF (Genbank No. OP905580, OP905581 and OP905582) and ACT (Genbank No. OP897308, OP897309 and OP897310) sequences of isolates Phy1, Phy2 and Phy3 shared up to 99%, 99%, 100% and 100% similarities with their counterparts (Genbank No. OP163688, MH051003, ON246258 and KY855652) in Phyllosticta capitalensis, respectively. To further confirm their identity, a neighbor-joining phylogenetic tree was generated using MEGA7. Based on morphological characteristics and sequence analysis, the three strains were identified as P. capitalensis. To fulfill Koch's postulates, conidial suspension (1×105 conidia per mL) collected from three isolates were independently inoculated on artificially wounded detached leaves and leaves on trees of Litsea cubeba. Leaves were inoculated with sterile distilled water as negative controls. The experiment was repeated three times. All pathogen-inoculated wounds exhibited necrotic lesions within 5 days on detached leaves and 10 days on the leaves growing on trees after inoculation, whereas no symptoms were observed on the controls. The pathogen was exclusively re-isolated from the infected leaves and showed identical morphological characteristics to those of the original pathogens. P. capitalensis is a destructive plant pathogen that has been shown to cause leaf spots or black patch symptoms on variety of host plants around the world (Wikee et al. 2013), including oil palm (Elaeis guineensis Jacq.), tea plant (Camellia sinensis), Rubus chingii and castor (Ricinus communis L.). To our knowledge, this is the first report of black patch disease of Litsea cubeba caused by P. capitalensis in China. This disease causes severe leaf abscission in fruit development stage of Litsea cubeba and leads to a large amount of fruit drop.

at Different Harvesting Times and Their Skin-Whitening Cosmetic Potential

Litsea cubeba fruit, which has the highest content of essential oils in the plant, is an important woody oil plant resource. In this study, the influence of the solvent-free microwave extraction (SFME) and hydrodistillation (HD) techniques on the extraction of L. cubeba fruit essential oils was investigated in terms of yield, kinetics, and chemical composition, where the former conditions were optimized by the response surface design. The maximal essential oil yield was obtained under the optimal SFME process conditions (442 W and 24 min), where the irradiation time was the most important variable (p < 0.0001). Regardless of the extraction method used, the influence of harvesting time on L. cubeba fruit essential oils were quantitatively and qualitatively analyzed afterwards, where the SFME essential oil from July showed its superiority over the others regarding its higher extraction yield and better bioactivities. Compared with the HD method, the SFME approach could significantly enhance the yield of essential oils extracted from June to August by nearly 47% with the advantages of saving energy and low environmental impact. Interestingly, the SFME method could selectively extract monoterpene hydrocarbons such as D-limonene with relation to different compositions and bioactivities. Moreover, SFME essential oil showed a better inhibitory effect on tyrosinase and melanogenesis, indicating its skin-whitening potential as a new promising natural cosmetic ingredient.

The leaves of the seasoning plant Litsea cubeba inhibit the NLRP3 inflammasome and ameliorate dextran sulfate sodium-induced colitis in mice

The intracellular sensor NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome controls caspase-1 activity and the maturation and release of the cytokines interleukin (IL)−1β and IL−18. The NLRP3 inflammasome has attracted the attention of the pharmaceutical industry because it promotes the pathogenesis of many diseases, making it a promising target for drug development. Litsea cubeba (Lour.) is a plant traditionally used as a seasoning in Taiwan and in other Asian countries. In this study, we investigated the inhibitory activity of the leaves of L. cubeba against the NLRP3 inflammasome. We found that the ethanol extract of L. cubeba leaves (MLE) inhibited the NLRP3 inflammasome in macrophages by reducing caspase−1 activation and IL−1β secretion. MLE reduced pyroptosis in macrophages and inhibited the release of NLRP3 and apoptosis-associated speck-like protein containing a CARD (ASC). In a mechanistic study, MLE reduced mitochondrial reactive oxygen species (ROS) production and preserved mitochondrial integrity, which led to reduced mitochondrial DNA release into the cytosol. MLE did not reduce the expression levels of NLRP3, IL−1β precursor or TNF-α in lipopolysaccharide (LPS)-activated macrophages. These results indicated that MLE inhibited the NLRP3 inflammasome by suppressing the activation signals of the NLRP3 inflammasome but not by reducing the priming signal induced by LPS. In addition, oral administration of MLE (20−80 mg/kg) ameliorated dextran sulfate sodium (DSS)−induced colitis in a mouse model. Notably, mice that received MLE (1 and 2 g/kg) daily for 7 days did not exhibit visible side effects. Gas chromatography-mass spectrometry (GC-MS) analysis found that α-Terpinyl acetate (27.2%) and 1,8−Cineole (17.7%) were the major compounds in MLE. These results indicated that L. cubeba leaves have the potential to be a nutraceutical for preventing and improving NLRP3 inflammasome-related diseases.

Role of Litsea cubeba Essential Oil in Agricultural Products Safety: Antioxidant and Antimicrobial Applications

The essential oil from Litsea cubeba (LCEO) has good antioxidant, antimicrobial, anti-insect properties, which gives it the potential for use as a natural additive to food resources and food products in order to prevent spoilage and extend shelf life. In this study the biological activity related to food preservation was observed. The main volatile organic compounds were geranial (39.4%), neral (29.5%), and limonene (14.3%). Antioxidant activity was 30.9%, which was equal to 167.94 µg of Trolox per mL of sample. Antimicrobial activity showed the strongest inhibition against Serratia marcescens by disk diffusion method and minimum inhibitory concentrations MIC 50 and MIC 90 were the lowest for Micrococcus luteus with values 1.46 and 3.52 µL/mL, respectively. Antimicrobial activity of the LCEO vapor phase showed strong inhibition of microorganisms on apples, pears, potatoes, and kohlrabies. Over 50% of gram-positive and gram-negative bacteria and yeasts were inhibited by a concentration of 500 µL/mL. The inhibition of microorganisms was concentration dependent. Anti-insect activity was also strong, with 100% lethality of Pyrrhocoris apterus at a concentration of 25%. These results suggest that LCEO could be potentially used as a food preservative.

First report of leaf spot disease caused by Fusarium oxysporum on Litsea cubeba in China

Litsea cubeba, an important industrial plant species that originated in China, produces fruit essential oil extensively applied in the chemical industry (Xiang et al. 2020). In July 2020, a large-scale outbreak of leaf spot disease on Litsea cubeba was first observed and then monitored over time in Yueyang (29°37'N; 113°13'E) and Changsha (28°06'N; 113°02'E), Hunan province, China. Symptoms of this disease consisted of round-shaped lesions that initially appeared as small light-brown spots. With the increase in number, these small spots coalesced into larger, dark-brown lesions leading to yellowing and abscission of the leaves. To identify the causal agent this disease, the pathogen was isolated with a tissue separation method (Gao et al. 2020). The infected leaf tissues surface-disinfected with 75% ethanol and 0.1% HgCl were aseptically cut into small pieces (11 cm) and then placed onto potato dextrose agar (PDA) medium with cephalothin (0.2 mg/ml) and incubated at 28°C for 3-5 days. The purified colonies on PDA exhibited fluffy white hyphae, secreted a dark red pigment that had been observed in previous studies (Xiao et al. 2015) and produced microconidia and macroconidia. The microconidia were single-celled, non-septate, ovoid, and ranged from 3.08 to 13.89 μm long and 2.17 to 3.62 μm wide (n=50). Macroconidia were three to five-septate, slightly curved, and ranged from 11.77 to 26.85 μm long and 3.31 to 4.50 μm wide (n=50). These morphological features suggested that theisolates were most likely Fusarium oxysporum (Savian et al. 2021). To further confirm the identity of this pathogen (designated as Fox-1), the TEF-1a gene (Genbank accession No. OM281065) and rDNA ITS region (Genbank accession No. OM250084) were cloned and then sequenced (Cui et al, 2021). Sequence alignments indicated that the ITS and TEF-1a sequences shared 99.8% (504/505) and 99.7% (665/667) similarities with that of F. oxysporum (Genbank accession No. MF667966, KT230848), respectively. Both of the morphological characteristics and molecular data were used to identify this pathogen as F. oxysporum Schltdl.: Fr. 1824. To further verify whether these isolates of F. oxysporum can cause leaf spot disease, Koch's postulates were tested (Gradmann 2014). The purified pathogens were inoculated on artificial wounds of detached Litsea cubeba leaves and the leaves on the field plants of Litsea cubeba, respectively. The wounds of leaves were inoculated with sterile distilled water as negative controls. The experiment was performed independently three times, each with three leaves and three inoculated wounds on each leaf. All pathogen-inoculated wounds developed dark brown or black lesions on detached leaves within 3 days and on leaves on plants within 9 days, whereas the controls showed no symptoms. Re-isolations from infected leaves confirmed that the re-isolated pathogens possessed identical morphological characteristics to those of the original pathogens. To our knowledge, this is the first report of leaf spot infection of Litsea cubeba caused by F. oxysporum in China. This disease severely delays plant development and significantly decreases the yield of essential oil of Litsea cubeba. Our results laid a foundation for the subsequent research into pathogenic mechanisms drug sensitivity tests, which will contribute to the prevention and cure of leaf spot disease of Litsea cubeba. References: Cui, L. X., et al. 2021. Plant Dis. 105:7. Gao, W., et al. 2020. Plant Dis. 105:501. Gradmann. 2014. J. Microbes Infect. 16:885-892. Savian, L. G., et al. 2021. Plant Dis. 104:1870. Xiang, Y. J., et al. 2020. J. Chin. Cereals Oils Assco. 35:186-195. Xiao, J. L., et al. 2015. Hunan Agric. Sci. 4:105-108.

Antibacterial Activity of the Essential Oil From Litsea cubeba Against Cutibacterium acnes and the Investigations of Its Potential Mechanism by Gas Chromatography-Mass Spectrometry Metabolomics

Cutibacterium acnes (C. acnes) is an anaerobic Gram-positive bacterium generally considered as a human skin commensal, but is also involved in different infections, such as acne and surgical infections. Although there are a variety of treatments, the side effects and the problem of bacterial drug resistance still limit their clinical usage. In this study, we found that essential oil (EO) distilled from fresh mature Litsea cubeba possessed promising antibacterial activity against C. acnes. In order to elucidate its potential mechanism, bacteriostatic activity test, Live/Dead kit assay, scanning electron microscope (SEM), transmission electron microscope (TEM), and metabolomics were employed. In addition, the content of adenosine triphosphate (ATP) in bacterium and the activities of key enzymes involved in critical metabolic pathways were detected using a variety of biochemical assays. The results showed that EO exhibited significant antibacterial activity against C. acnes at a minimum inhibitory concentration (MIC) of 400 μg/mL and a minimum bactericidal concentration (MBC) of 800 μg/mL, and EO could destroy C. acnes morphology and inhibit its growth. Moreover, results from our study showed that EO had a significant effect on the C. acnes normal metabolism. In total, 86 metabolites were altered, and 34 metabolic pathways related to the carbohydrate metabolism, energy metabolism, amino acid metabolism, as well as cell wall and cell membrane synthesis were perturbed after EO administration. The synthesis of ATP in bacterial cells was also severely inhibited, and the activities of key enzymes of the glycolysis and Wood-Werkman cycle were significantly affected (Pyruvate Carboxylase, Malate Dehydrogenase and Pyruvate kinase activities were decreased, and Hexokinase was increased). Taken together, these results illustrated that the bacteriostatic effect of EO against C. acnes by breaking the bacterial cell morphology and perturbing cell metabolism, including inhibition of key enzyme activity and ATP synthesis. The results from our study may shed new light on the discovery of novel drugs with more robust efficacy.

Comprehensive identification of bHLH transcription factors in Litsea cubeba reveals candidate gene involved in the monoterpene biosynthesis pathway

Litsea cubeba (Lour.) Person, an economically important aromatic plant producing essential oils, has lemon-like fragrance and 96.44-98.44% monoterpene contents. bHLH transcription factor plays an important role in plant secondary metabolism and terpene biosynthesis. In this study, we used bioinformatics to identify bHLH transcription factors in L. cubeba, 173 bHLH genes were identified from L. cubeba and divided these into 26 subfamilies based on phylogenetic analysis. The majority of bHLHs in each subfamily shared comparable structures and motifs. While LcbHLHs were unevenly distributed across 12 chromosomes, 10 tandem repeats were discovered. Expression profiles of bHLH genes in different tissues demonstrated that LcbHLH78 is a potential candidate gene for regulating monoterpene biosynthesis. LcbHLH78 and the terpene synthase LcTPS42 showed comparable expression patterns in various tissues and fruit development stages of L. cubeba. Subcellular localization analysis revealed that LcbHLH78 protein localizes to the nucleus, consistent with a transcription factor function. Importantly, transient overexpression of LcbHLH78 increased geraniol and linalol contents. Our research demonstrates that LcbHLH78 enhances terpenoid biosynthesis. This finding will be beneficial for improving the quality of L. cubeba and provides helpful insights for further research into the control mechanism of LcbHLH genes over terpenoid biosynthesis.

Bioactive sesquineolignans from the twigs of Litsea cubeba

In a continuing search for biological natural products with structure diversity from traditional Chinese herbs, five new sesquineolignans (1-5) were isolated from an ethyl acetate extract of the twigs of Litsea cubeba. Their structures were elucidated based on MS, 1D and 2D NMR spectroscopic data, as well as experimental electronic circular dichroism (ECD) spectra. Compounds 1-5 showed moderate inhibitory effects against LPS-induced NO production in RAW264.7 macrophages, with IC₅₀ values of 16.2, 20.2, 22.1, 15.1, and 16.6 μmol·L^-1, respectively.

Plant-derived bioactive compounds produced by Streptomyces variabilis LCP18 associated with Litsea cubeba (Lour.) Pers as potential target to combat human pathogenic bacteria and human cancer cell lines

To date, endophytic actinomycetes have been well-documented as great producers of novel antibiotics and important pharmaceutical leads. The present study aimed to evaluate potent bioactivities of metabolites synthesized by the strain LCP18 residing in the Vietnamese medicinal plant Litsea cubeba (Lour.) Pers towards human pathogenic bacteria and human cancer cell lines. Endophytic actinomycete strain LCP18 showed considerable inhibition against seven bacterial pathogens and three human tumor cell lines and was identified as species Streptomyces variabilis. Strain S. variabilis LCP18 was phenotypically resistant to fosfomycin, trimethoprim-sulfamethoxazole, dalacin, cefoxitin, rifampicin, and fusidic acid and harbored the two antibiotic biosynthetic genes such as PKS-II and NRPS. Further purification and structural elucidation of metabolites from the LCP18 extract revealed five plant-derived bioactive compounds including isopcrunetin, genistein, daidzein, syringic acid, and daucosterol. Among those, isoprunetin, genistein, and daidzein exhibited antibacterial activity against Salmonella typhimurium ATCC 14,028 and methicillin-resistant Staphylococcus epidermidis ATCC 35,984 with the MIC values ranging from 16 to 128 µg/ml. These plant-derived compounds also exhibited cytotoxic effects against human lung cancer cell line A549 with IC50 values of less than 46 μM. These findings indicated that endophytic S. variabilis LCP18 can be an alternative producer of plant-derived compounds which significantly show potential applications in combating bacterial infections and inhibition against lung cancer cell lines.

The effect of an isoquinoline alkaloid on treatment of periodontitis by regulating the neutrophils chemotaxis

Neutrophil plays a critical role in the progression of periodontitis. In general, its chemotaxis and activation are benefit for the host defense of bacterial infection and inflammation. However, previous studies have reported that the hyperactive and reactive neutrophils appear to be one of the reasons for tissue destruction in periodontitis tissues. In this study, we investigated an isoquinoline alkaloid Litcubanine A (LA), which from the Traditional Chinese medicinal plant, Litsea cubeba. We found LA showed significant activity in inhibiting neutrophils chemotaxis in the zebrafish yolk sac microinjection model in vivo and in mouse neutrophils in vitro. Further investigation proved that LA could inhibit the expression levels of neutrophil respiratory burst-related and inflammation-related genes CYBB and NCF2, as well as inhibit the activation of MAPK signaling pathway. Moreover, using LA, we successfully achieved the effect of reducing periodontitis bone loss by regulating neutrophil chemotaxis and related functions in a mouse ligature-induced periodontitis model.

Novel Isoquinoline Alkaloid Litcubanine A - A Potential Anti-Inflammatory Candidate

Macrophages play a critical role in innate and adaptive immunity, and the regulation of macrophage function in inflammatory disease treatment has been widely studied. Litsea cubeba is an important Chinese medicinal plant used for the treatment of inflammatory diseases. However, the inflammatory bioactive ingredients in L. cubeba and underlying molecular mechanisms are poorly understood. Herein, we first obtained and elucidated a novel isoquinoline alkaloid, Litcubanine A (LA), from L. cubeba. An in vitro study indicated that LA could significantly inhibit LPS-induced activation of inflammatory macrophages via the NF-κB pathway, leading to the decrease of inflammatory factors including iNOS, TNF-α, and IL-1β. Moreover, LA showed an inhibiting effect on the expression of NO in macrophages by directly binding to iNOS protein. Molecular simulation docking also demonstrated that active LA created an interaction with GLU 371 residue of iNOS via attractive charge derived from the N→O group, revealing its highly selective inhibition toward iNOS. By using the IκK inhibitor and iNOS inhibitor, these two regulatory targets of LA on inflammatory macrophages were verified in vitro. Finally, by using a caudal fin resection model in zebrafish larvae, and the skin wound healing model in mice, we proved in vivo that LA down-regulated the secretion of local inflammatory factors by inhibiting macrophage recruitment and activation at the early stage of the injury. Collectively, our study demonstrated that the novel isoquinoline alkaloid LA suppresses LPS-induced activation of inflammatory macrophages by modulating the NF-κB pathway, suggesting that inflammatory macrophage activation pathway is an effective target for inflammation treatment, and LA is a new pharmacophore for the development of novel and effective anti-inflammatory agents to regulate local macrophages.

Microemulsification of essential oils for the development of antimicrobial and mosquito repellent functional coatings for textiles

AIMS

To develop an essential oil (EO)-loaded textile coating using an environmentally friendly microemulsion technique to achieve both antimicrobial and mosquito repellent functionalities.

METHODS AND RESULTS

Minimum inhibitory concentrations and fractional inhibitory concentrations of litsea, lemon and rosemary EOs were determined against Staphylococcus aureus, Escherichia coli, Staphylococcus epidermidis, Pseudomonas aeruginosa and Trichophyton rubrum. A 1 : 2 mixture of litsea and lemon EOs inhibited all the microorganisms tested and was incorporated into a chitosan-sodium alginate assembly by a microemulsification process. The EO-loaded microemulsions were applied to cotton and polyester fabrics using a soak-pad-dry method. The textile challenge tests demonstrated 7-8 log₁₀ reductions of S. epidermidis, S. aureus and E. coli after 24 h and T. rubrum after 48 h. Aedes aegypti mosquito repellency was also assessed which demonstrated 71·43% repellency compared to 52·94% by neat EO-impregnated cotton.

CONCLUSIONS

Textiles treated with the litsea and lemon EO microemulsion showed strong antimicrobial activity against the skin associated microorganisms E. coli, S. aureus, S. epidermidis and T. rubrum and potential mosquito repellent properties.

SIGNIFICANCE AND IMPACT OF THE STUDY

EOs could be useful for the development of natural, environmentally friendly functional textiles to protect textiles and users from microbial contamination in addition to possessing other beneficial properties such as mosquito repellency.

fruits and its chemical composition and biological activity

As an important natural product, the sufficient separation of plant essential oil (EO) is helpful to improve its utilization value. In this work, deep eutectic solvent-homogenate based microwave-assisted hydrodistillation (DES-HMAHD) was developed and applied to isolate EO from the fruits of Litsea cubeba (Lour.) Pers. Different types of DES were investigated in terms of the EO kinetics and composition, among which oxalic acid/choline chloride (OA/ChCl) had obvious advantages. Following, molar ratio of OA and ChCl (1:1), water content (50%), liquid-solid ratio (12.5:1 mL/g), homogenate time (2 min), and microwave power (700 W) were found to be the optimum conditions. Gas chromatography-mass spectrometer (GC-MS) analysis showed that the EO isolated from DES-HMAHD contained a large proportion of m-cymene and trans-linalool oxide, which were quite different from the conventionally reported L. cubeba EO. In addition, the proposed DES-HMAHD resulted in higher separation efficiency and economic value, as well as lower environmental impact, as compared with other techniques. Afterwards, the EO isolated by different methods was evaluated from the perspective of biological activity. The EO obtained by DES-HMAHD showed higher antioxidant activity (DPPH and ABTS) but lower antifungal activity, which was related to its chemical composition. In general, DES-HMAHD produced a kind of L. cubeba EO with different components, which provided a scientific foundation for the sufficient isolation of plant EO and its application in the natural products.

Litsea cubeba essential oil: chemical profile, antioxidant activity, cytotoxicity, effect against Fusarium verticillioides and fumonisins production

The purpose of this study was to determine the chemical profile of Litsea cubeba essential oil, carry out an in vitro evaluation of its antioxidant potential and its cytotoxicity, as well as its antifungal and antimicotoxigenic activities against Fusarium verticillioides. Most of the compounds observed in the EO were neral (32.75%) and geranial (37.67%). The radical scavenging capacity of 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid was 104.4 and 56.4 mmol Trolox mg^-1, respectively, indicating good antioxidant activity. The EO studied by us revealed cytotoxic effect against HT-29 and HeLa cancer cells. The Minimum Inhibitory and Minimum Fungicidal Concentrations against F. verticillioides were both 125 µg mL^-1. Morphological investigation, performed by fluorescence microscopy and scanning electron microscopy, showed that hyphae and microconidia structures underwent changes after treatment with the EO. Analyses performed with the EO strongly reduced the mycelial development of F. verticillioides and the synthesis of fumonisins B₁ and B₂ in dose-dependence effect compared (P < 0.01) with the fungal control (10⁵ conidia mL^-1) and positive control (fludioxonil + metalaxyl-M). Thus, the results obtained in vitro suggest that L. cubeba EO has excellent antioxidant, fungicidal, and antimycotoxigenic effects.

[Chemical constituents from ethyl acetate soluble extraction of Litsea cubeba]

Chemical investigation on the constituents of the ethyl acetate soluble extraction of Litsea cubeba has resulted in the isolation and structure elucidation of thirty compounds, including one sesquiterpene(1), four monoterpenes(2-5), two γ-butyrolactone derivatives(6 and 7), seven tyramine derivatives(8-14), fifteen aromatic compounds(15-29), and one pyrone derivative(30) via various chromatographic techniques and spectroscopic data analysis(MS, IR, 1 D and 2 D NMR). Compounds 1-7, 13 and 14 were obtained from the genus Litsea for the first time.

Litsea cubeba fruit essential oil and its major constituent citral as volatile agents in an antimicrobial packaging material

Food packaging films were coated with polyvinyl acetate (PVA) containing different concentrations of citral or Litsea (L.) cubeba essential oil (EO). Antimicrobial contact trials in style of ISO22916 were performed. Citral coatings achieved bactericidal effects against Escherichia coli (2.1 log) and Staphylococcus aureus (4.3 log) at concentrations of 20%_DM. L. cubeba inactivated more than 4 log cycles of both bacteria at a concentration of 20%_DM. To determine the antimicrobial activity across the gas phase, a unique method for volatile agents was developed, adapting ISO22196. GC/MS measurements were performed to supplement microbiological tests in a model packaging system with a defined 220 ml headspace (HS). HS-equilibrium concentrations of 1.8 μg/ml_Air were found for 20%_{DM '}citral-coatings, resulting in antimicrobial effects of 3.8 log against of E. coli. Saccharomyces cerevisiae (4.74 log) and Aspergillus niger (4.29 log) were more effectively inactivated by 3%_DM and 5%_DM coatings. In an application trial with strawberries, simulating a headspace packaging, growth inhibitory effects on the yeast and mold microbiota were found for the 20%_DM coatings.

The complete chloroplast genome sequence of Litsea cubeba

The first complete chloroplast genome (cpDNA) sequence of Litsea cubeba was determined from Illumina HiSeq pair-end sequencing data in this study. The cpDNA is 152,725 bp in length, contains a large single-copy region (LSC) of 93,673 bp, and a small single-copy region (SSC) of 18,924 bp, which were separated by a pair of inverted repeats (IR) regions of 20,064 bp, each. The genome contains 126 genes, including 82 protein-coding genes, 8 ribosomal RNA genes, and 36 transfer RNA genes. The further phylogenomic analysis showed that L. cubeba and Litsea garrettii clustered in a clade in Lauraceae family.

Anti-Infectious Plants of The Thai Karen: A Meta-Analysis

Pharmacology has developed many drugs to treat infections, but many people, especially in developing countries, cannot afford to purchase them, and still depend on traditional knowledge and local medicinal plants to fight off infections. In addition, numerous microbes have developed resistance to the pharmaceutical drugs developed to fight them, and for many, such as Covid-19, effective drugs remain to be found. Ethnomedicinal knowledge is useful, not only for local people as a source of medicine for primary health care, but also for new pharmacological discoveries. This study aimed to identify the plants that the Karen, the largest hill-tribe ethnic minority in northern and western Thailand, use for treatments of infectious diseases. We present a meta-analysis of data from 16 ethnobotanical studies of 25 Karen villages with the aim of understanding traditional knowledge and treatments and point to potential plants for further pharmacological development. The Karen used 127 plant species from 59 plant families to treat infections and infectious diseases. The Cultural Important Index (CI) showed that the Leguminosae, Euphorbiaceae, Asteraceae, Lauraceae, Apocynaceae, Menispermaceae, and Lamiaceae were the most commonly used families. As for species, Cleidion javanicum, Tinospora crispa, Litsea cubeba, Aesculus assamica, Tadehagi triquetrum, Senna alata, Tithonia diversifolia, Embelia sessiliflora, and Combretum indicum were the most commonly used in treatments of infectious diseases. We suggest that these plant species should be the first to be pharmacologically tested for possible development of medicines, and the remaining species registered should subsequently undergo testing.

Evaluation of antioxidant activities, toxicity studies and the DNA damage protective effect of various solvent extracts of Litsea cubeba fruits

Litsea cubeba is devoured by the ethnic individuals of Arunachal Pradesh in India as food and has been traditionally used for curing different ailments. The purpose of present study was to investigate the antioxidant activities of fruits of L. cubeba using different solvent extracts, quantification of phenolics, toxicity studies and DNA damage protective activities. The antioxidant activities of fruits using five different solvent extracts completed utilizing different in vitro examines. The quantitation of phenolic and polyphenolic compounds in the methanol extract of the fruits was carried out by HPLC. The in vitro haemolytic examination of plant concentrates were completed on rat erythrocytes. Appraisal of cytotoxicity of eatable fruits was assessed by MTT measure. The genotoxicity of the contemplated plant was tried by the single-cell gel electrophoresis comet measure. The DNA defensive impacts of the aqueous extracts of fruits on rodent lymphocyte DNA lesions were likewise assessed with the comet test. The extract obtained by methanol exhibited the highest antioxidant activity. The HPLC examination of the methanol concentrate of the plant demonstrated the occurrence of different phenolic acids and flavonoids like caffeic acid (145.96μg/100mg DE), syringic acid (125.85 μg/100mg DE), ferulic acid (155.89 μg/100mg DE), apigenin (28.43 μg/100mg DE), kaempferol (53.41 μg/100mg DE) etc. in various amounts. The consequences of haemolytic lethality, cytotoxicity and genotoxicity of fluid concentrates of the edible plant ensure the security at cell and genomic level. The fluid concentrate of the plant fundamentally repressed DNA harm and these information recommend that the watery concentrate of L. cubeba can forestall oxidative DNA harm to rodent lymphocytes, which is likely because of antioxidant constituents in the concentrate. These outcomes demonstrate that L. cubeba can be utilized in dietary applications with a possibility to diminish oxidative pressure.

A Model of Hormonal Regulation of Stamen Abortion during Pre-Meiosis of Litsea cubeba

Litsea cubeba (Lour.) Pers., a popular essential oil plant, is a dioecious species with degenerative sexual organs in both male and female individuals. Yet, the mechanism of degenerative organs development in male and female flowers is poorly understood. Here, we analyzed the morphological characters of degenerative organ development by morphological and histological observations, and determined the critical stage of abortion that occurs at pre-meiosis in male and female flowers. We also conducted RNA sequencing (RNA-seq) to understand the genetic basis of stamen abortion in female flowers. The differentially expressed genes (DEGs) were identified during the staminode development in female flowers; functional enrichment analysis revealed some important biological pathways involved the regulation of stamen abortion, including plant hormone signal transduction, phenylpropanoid biosynthesis, flavonoid biosynthesis and monoterpenoid biosynthesis. Furthermore, 15 DEGs involved in the hormone pathways were found to regulate stamen development. By HPLC-MS/MS analysis, there were a salicylic acid (SA) content peak and the gibberellin (GA) content lowest point in the abortion processes in female flowers, suggesting a vital function of hormonal processes. Co-expression network analysis further identified several hub genes that potentially played significant roles in the stamen abortion of L. cubeba. Taken together, we proposed a model involved in plant hormones pathways underlying stamen abortion during pre-meiosis in female flowers of L. cubeba.

Characterization of Endophytic Streptomyces griseorubens MPT42 and Assessment of Antimicrobial Synergistic Interactions of its Extract and Essential Oil from Host Plant Litsea cubeba

The present study aimed to evaluate the synergistic effects of the crude ethyl acetate extract (CEAE) from endophytic actinomycete MPT42 and essential oil (EO) of the same host plant Litsea cubeba. The isolate MPT42, exhibiting broad-spectrum antimicrobial activities and harboring all three antibiotic-related biosynthetic genes pks-I, pks-II, and nrps, was identified as Streptomycete griseorubens based on an analysis of the morphology, physiology, and 16S rDNA sequence. Minimum inhibitory concentrations (MICs) and the fractional inhibitory concentration index were used to estimate the synergistic effects of various combined ratios between CEAE or antibiotics (erythromycin, vancomycin) and EO toward 13 microbial strains including pathogens. L. cubeba fruit EO, showing the main chemical constituents of 36.0% citral, 29.6% carveol, and 20.5% limonene, revealed an active-low against tested microbes (MICs ≥ 600 μg/mL). The CEAE of S. griseorubens culture exhibited moderate–strong antimicrobial activities against microbes (MICs = 80–600 μg/mL). Analysis of the mechanism of action of EO on Escherichia coli ATCC 25922 found that bacterial cells were dead after 7 h of the EO treatment at 1 MIC (5.5 mg/mL), where 62% cells were permeabilized after 2 h and 3% of them were filament (length ≥ 6 μm). Combinations of CEAE, erythromycin, or vancomycin with EO led to significant synergistic antimicrobial effects against microbes with 4–16 fold reduction in MIC values when compared to their single use. Interestingly, the vancomycin–EO combinations exhibited a strong synergistic effect against five Gram-negative bacterial species. This could assume that the synergy was possibly due to increasing the cell membrane permeability by the EO acting on the bacterial cells, which allows the uptake and diffusion of antimicrobial substances inside the cell easily. These findings in the present study therefore propose a possible alternative to combat the emergence of multidrug-resistant microbes in veterinary and clinics.

[Water soluble constituents from the twigs of Litsea cubeba]

Twenty five known aromatic glycosides (1-25) and three known sesquiterpene glycosides (26-28) have been isolated from the twigs of Litsea cubeba by using various chromatographic techniques. Their structures were identified by spectroscopic data analysis (MS, IR, 1D and 2D NMR) as (7S,8R)-dehydrodiconiferyl alcohol 4,9'-di-O-β-D-glucopyranoside(1),(7S,8R)-5-methoxydihydrodehydrodiconiferyl alcohol 4-O-β-D-glucopyranoside(2), (7S,8R)-urolignoside(3), (7R,8S)-dihydrodehydrodiconiferyl alcohol 4-O-β-D-glucopyranoside(4), saposide B(5), lanicepside A(6), matairesinol-4-O-β-D-glucopyranoside (7), tyraxjaponoside B(8), (+)-lyoniresinol-9'-O-β-D-glucopyranoside (9), alaschanisoside A (10), syringin (11), psoralenoside (12), isopsoralenoside (13), scopolin(14), 2,6-dimethoxy-4-hydroxyphenol-1-O-β-D-glucopyranoside (15), 3-hydroxy-4,5-dimethoxyphenyl-β-D-glucopyranoside (16), 2-(3,4-dihydroxyphenyl)ethyl-β-D-glucopyrnoside (17), 2-(4-dihydroxyphenyl)ethyl-β-D-glucopyranoside (18), (+)-catechin-7-O-β-D-glucopyranoside (19), 3'-O-methylepicatechin-7-O-β-D-glucopyranoside (20), kaempferitrin (21), quercetin-3-O-α-L-rhamnopyranside (22), kaempferol-3-O-β-D-glucopyranoside (23), kaempferol 3-O-β-D-glucopyranosyl(1→2)-O-β-D-galactopyr anoside-7-O-α-L-rhamnopyranoside (24), quercetin 3-O-α-L-rhamnopyranosyl(1→6)-O-β-D-glucopyranosyl(1→3)-O-α-L-rhamnopyranosyl(1→2)-O-β-D-glucopyranoside (25), staphylionoside D(26), vomifoliol 9-O-β-D-glucopyranoside (27), dihydrovomifoliol-O-β-D-glucopyranoside (28). Compounds 1-21 and 24-28 were obtained from this genus for the first time.

Chemical composition, antimicrobial activity and antioxidant activity of Litsea cubeba essential oils in different months

In this study, the chemical composition, antimicrobial and antioxidant activities of Litsea cubeba essential oils extracted in different months were analysed. Results showed that the essential oil contents of fruits collected in June, July and August were 3.47%, 5.02% and 5.64%, respectively, and contained 13, 17 and 17 components, respectively. Neral and geranial were the main components and accounted for 54.76%. The essential oil extracted from fruits collected in July had the highest antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium, and it was the most effective based on the OH· scavenging activity test. The essential oil extracted from fruits collected in August was the most effective based on the test for DPPH· scavenging activity and ferric reducing antioxidant power. Considering the contents, chemical compositions and antimicrobial and antioxidant activities, the appropriate harvest time for L. cubeba essential oils is from July to August.

Evaluation of the Anti-Trypanosomal Activity of Vietnamese Essential Oils, with Emphasis on Curcuma longa L. and Its Components

Human African trypanosomiasis (HAT), known as sleeping sickness and caused by Trypanosoma brucei, is threatening low-income populations in sub-Saharan African countries with 61 million people at risk of infection. In order to discover new natural products against HAT, thirty-seven Vietnamese essential oils (EOs) were screened for their activity in vitro on Trypanosoma brucei brucei (Tbb) and cytotoxicity on mammalian cells (WI38, J774). Based on the selectivity indices (SIs), the more active and selective EOs were analyzed by gas chromatography. The anti-trypanosomal activity and cytotoxicity of some major compounds (isolated or commercial) were also determined. Our results showed for the first time the selective anti-trypanosomal effect of four EOs, extracted from three Zingiberaceae species (Curcuma longa, Curcuma zedoaria, and Zingiber officinale) and one Lauraceae species (Litsea cubeba) with IC₅₀ values of 3.17 ± 0.72, 2.51 ± 1.08, 3.10 ± 0.08, and 2.67 ± 1.12 nL/mL respectively and SI > 10. Identified compounds accounted for more than 85% for each of them. Among the five major components of Curcuma longa EO, curlone is the most promising anti-trypanosomal candidate with an IC₅₀ of 1.38 ± 0.45 µg/mL and SIs of 31.7 and 18.2 compared to WI38 and J774 respectively.

Lignans from the Twigs of Litsea cubeba and Their Bioactivities

Litsea cubeba, an important medicinal plant, is widely used as a traditional Chinese medicine and spice. Using cytotoxicity-guided fractionation, nine new lignans 1–9 and ten known analogues 10–19 were obtained from the EtOH extract of the twigs of L. cubeba. Their structures were assigned by extensive 1D- and 2D-NMR experiments, and the absolute configurations were resolved by specific rotation and a combination of experimental and theoretically calculated electronic circular dichroism (ECD) spectra. In the cytotoxicity assay, 7′,9-epoxylignans with feruloyl or cinnamoyl groups (compounds 7–9, 13 and 14) were selectively cytotoxic against NCI-H1650 cell line, while the dibenzylbutyrolactone lignans 17–19 exerted cytotoxicities against HCT-116 and A2780 cell lines. The results highlighted the structure-activity relationship importance of a feruloyl or a cinnamoyl moiety at C-9′ or/and C-7 ketone in 7′,9-epoxylignans. Furthermore, compound 11 was moderate active toward protein tyrosine phosphatase 1B (PTP1B) with an IC₅₀ value of 13.5 μM, and compounds 4–6, 11 and 12 displayed inhibitory activity against LPS-induced NO production in RAW264.7 macrophages, with IC₅₀ values of 46.8, 50.1, 58.6, 47.5, and 66.5 μM, respectively.

Transcriptome Analysis of Litsea cubeba Floral Buds Reveals the Role of Hormones and Transcription Factors in the Differentiation Process

BACKGROUND

Litsea cubeba (Lour.) Pers. is an important economic plant that is rich in valuable essential oil. The essential oil is often used as a raw material for perfumes, food additives, insecticides and bacteriostats. Most of the essential oil is contained in the fruit, and the quantity and quality of fruit are dependent on the flowers. To explore the molecular mechanism of floral bud differentiation, high-throughput RNA sequencing was used to detect differences in the gene expression of L. cubeba female and male floral buds at three differentiation stages.

RESULTS

This study obtained 160.88 Gbp of clean data that were assembled into 100,072 unigenes, and a total of 38,658 unigenes were annotated. A total of 27,521 simple sequence repeats (SSRs) were identified after scanning the assembled transcriptome, and the mono-nucleotide repeats were predominant, followed by di-nucleotide and tri-nucleotide repeats. A total of 12,559 differentially expressed genes (DEGs) were detected from the female (F) and male (M) floral bud comparisons. The gene ontology (GO) databases revealed that these DEGs were primarily contained in "metabolic processes", "cellular processes", and "single-organism processes". The Kyoto Encyclopedia of Genes and Genomes (KEGG) databases suggested that the DEGs belonged to "plant hormone signal transduction" and accounted for a relatively large portion in all of these comparisons. We analyzed the expression level of plant hormone-related genes and detected the contents of several relevant plant hormones in different stages. The results revealed that the dynamic changes in each hormone content were almost consistent with the expression levels of relevant genes. The transcription factors selected from the DEGs were analyzed. Most DEGs of MADS-box were upregulated and most DEGs of bZIP were downregulated. The expression trends of the DEGs were nearly identical in female and male floral buds, and qRT-PCR analysis revealed consistency with the transcriptome data.

CONCLUSIONS

We sequenced and assembled a high-quality L. cubeba floral bud transcriptome, and the data appeared to be well replicated (n = 3) over three developmental time points during flower development. Our study explored the changes in the contents of several plant hormones during floral bud differentiation using biochemical and molecular biology techniques, and the changes in expression levels of several flower development related transcription factors. These results revealed the role of these factors (i.e., hormones and transcription factors) and may advance our understanding of their functions in flower development in L. cubeba.

Litsea cubeba leaf essential oil from Vietnam: chemical diversity and its impacts on antibacterial activity

The threat of bacterial resistance to antibiotics has created an urgent need to develop new antimicrobials. The aim of this study was to characterize the chemical diversity of Litsea cubeba leaf essential oil (EO) and its impacts on the antibacterial activity against pathogenic bacteria. Essential oils collected from seven provinces in North Vietnam (n = 25) were characterized by their high content in either 1,8-cineole or linalool. Linalool-type EOs were more effective against the eight bacterial strains tested than 1,8-cineole-type. Oil samples, LC19 (50% 1,8-cineole) and BV27 (94% linalool), were selected to investigate their antibacterial mechanisms against Escherichia coli. A strong bactericidal effect was observed after 4 and 2 h of exposure respectively. Microscopic analysis of treated E. coli cultures clearly showed that EOs caused changes in cell morphology, loss of integrity and permeability of the cell membrane, as well as DNA loss. However, the effects of both EOs were distinct. LC19 mostly affected cell membrane, led to a significant cell filamentation rate and altered cell width, whereas BV27 damaged cell membrane integrity leading to cell permeabilization and altered nucleoid morphology with the appearance of spot and visibly altered compaction.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study aimed to characterize the chemical diversity of Litsea cubeba leaf essential oil (EO) and its impacts on its antibacterial activity. Two major chemotypes (1,8-cineole or linalool rich) were identified in North Vietnam and both were bactericidal against several pathogenic bacteria. A distinct inhibitory effect of EO samples on Escherichia coli was observed. 1,8-cineole-rich sample (LC19) affected cell membrane, led to cell filamentation and perturbation of cell width, while the linalool-rich one (BV27) induced damages in the cell membrane and changes in the nucleoid morphology. The study demonstrates the importance of considering chemotype variations in terms of chemical composition as well as the mode of action.

A new N-methoxyl-carbonyl benzylisoquinoline from Litsea cubeba

A new benzylisoquinoline alkaloid (•)-N-methoxycarbonyl-norjuziphine (1) was isolated from Litsea cubeba. Its structure was identified by extensively spectroscopic techniques and confirmed by the single-crystal X-ray diffraction analysis. Compound 1 showed cytotoxicity against HL-60 and MCF-7 cells, with IC₅₀ values of 18.1 and 15.0 μM, respectively, comparable to 3.1 and 17.5 μM of the cisplatin (positive control).

citriodora)

The volatile compounds obtained from the different organs of Houttuynia cordata (Saururaceae) and Litsea cubeba (Lauraceae) were analyzed by Gas Chromatography/Mass Spectrometry (GC/MS), Headspace Solid Phase Micro Extraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS), and GC/olfactometry (GC/O). The major component of all parts of H. cordata is assigned as 4-tridecanone. Each organ produces myrcene as the major monoterpenoid. The major monoterpene in the rhizomes and roots was β-pinene instead of myrcene. 1-Decanal which was responsible for the unpleasant odor of this plant, was the predominant polyketide in both leaves and stems. The presence of 1-decanal was very poor in flowers, stem collected in summer, rhizomes, and roots. GC/MS analyses were very simple in case of the crude extracts of flowers. The content of sesquiterpenoids was extremely poor. (8Z)-Heptadecene, geranial, and neral were detected as the major components in Litsea cubeba. Odor-contributing components by GC/O analysis of the ether extract of the fresh flowers of L. cubeba were neral and geranial which played an important role in sweet-lemon fragrance of the flowers. The role of a high content of (8Z)-heptadecene was still unknown but it might play a significant role in the dispersion of the volatile monoterpene hydrocarbons and aldehydes. The flower volatiles of the Japanese L. cubeba were chemically quite different from those of the Chinese same species.

Essential Oil on Dendritic Cell and Contact Hypersensitivity Responses

Litsea cubeba L., also named as Makauy, is a traditional herb and has been used as cooking condiment or tea brewing to treat diseases for aborigines. The present study was undertaken to explore the chemical compositions of the fruit essential oil of L. cubeba (LCEO) and the immunomodulatory effect of LCEO on dendritic cells and mice. The LCEO was analyzed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) with direct injection (DI/GC) or headspace-solid phase microextraction (HS-SPME/GC). In total, 56 components were identified, of which 48 were detected by DI/GC and 49 were detected by HS-SPME/GC. The principal compounds were citral (neral and geranial). An immunosuppressive activity of LCEO was investigated with bone marrow-derived dendritic cells (DCs) which have a critical role to trigger the adaptive immunity. Additionally, the inhibitory effect of LCEO on immune response was elucidated by performing the contact hypersensitivity (CHS) responses in mice. Our results clearly showed that LCEO decreases the production of TNF-α and cytokine IL-12 in a dose-dependent manner in lipopolysaccharide (LPS)-stimulated DCs. CHS response and the infiltrative T cells were inhibited in the tested ears of the mice co-treated with LCEO. We demonstrate, for the first time, that the LCEO mainly containing citral exhibits an immunosuppressive effect on DCs and mice, indicating that LCEO can potentially be applied in the treatment of CHS, inflammatory diseases, and autoimmune diseases.

Antibacterial activity of Litsea cubeba (Lauraceae, May Chang) and its effects on the biological response of common carp Cyprinus carpio challenged with Aeromonas hydrophila

AIMS

The aims of this study were to characterize the antibacterial activity and the chemotype of Litsea cubeba leaf essential oil (EO) harvested in North Vietnam and to investigate the biological effects induced by the leaf powder on growth, nonspecific immunity and survival of common carp (Cyprinus carpio) challenged with Aeromonas hydrophila.

METHODS AND RESULTS

The EO showed the prevalence of linalool (95%, n = 5). It was bactericidal against the majority of tested strains, with minimum inhibitory concentrations ranging from 0·72 to 2·89 mg ml(-1) (Aer. hydrophila, Edwarsiella tarda, Vibrio furnissii, Vibrio parahaemolyticus, Streptococcus garvieae, Escherichia coli, Salmonella Typhimurium). The fish was fed with 0 (control), 2, 4 and 8% leaf powder supplementation diets for 21 days. Nonspecific immunity parameters (lysozyme, haemolytic and bactericidal activities of plasma) were assessed 21 days after feeding period and before the experimental infection. Weight gain, specific growth rate and feed conversion ratio were improved by supplementation of L. cubeba in a dose-related manner, and a significant difference appeared at the highest dose (8%) when compared to the control. The increase in plasma lysozyme was significant for all the treated groups. Haemolysis activity was higher for the groups fed with 4 and 8% plant powder. Antibacterial activity increased significantly for the 8% dose only.

CONCLUSIONS

Litsea cubeba leaf powder increased nonspecific immunity of carps in dose-related manner. After infection with Aer. hydrophila, survivals of fish fed with 4 and 8% L. cubeba doses were significantly higher than those fed with 2% dose and the control.

SIGNIFICANCE AND IMPACT OF THE STUDY

A range of 4-8% L. cubeba leaf powder supplementation diet (from specific linalool-rich chemotype) can be used in aquaculture to reduce antibiotic burden and impacts of diseases caused by Aer. hydrophila.

Chemical constituents from the roots and stems of Litsea cubeba

A new monoterpene and a new lignan, named litsecols A and B (1 and 2), respectively, together with nine known compounds (3-11), were isolated in a continuous investigation on the roots and stems of Litsea cubeba. Their structures were elucidated on the basis of extensive spectroscopic data analysis, and the absolute configuration of 1 was resolved by X-ray diffraction analysis. Compounds 2-5 and 7-9 showed significant inhibitory activity against nitric oxide (NO) production in lipopolysaccharide (LPS)-induced murine microglial (Bv-2) cell line. Compounds 10 and 11 exhibited significant neuroprotective effect against hydrogen peroxide-induced oxidative damage in rat adrenal pheochromocytoma (PC12) cell line.

Synergistic repellent and irritant effect of combined essential oils on Aedes aegypti (L.) mosquitoes

This study was designed to compare the behavioral responses of Aedes aegypti to a single essential oil and to a mixture of two or three essential oils using an excito-repellency test chamber. Mixtures were prepared from essential oils extracted from Litsea cubeba (LC), Litsea salicifolia (LS), and Melaleuca leucadendron (ML). In general, the mixture of essential oils produced a much stronger escape response by Ae. aegypti, regardless of the test conditions. No significant difference in escape responses was seen when the mixture of oils was compared with a standard commercial product containing DEET. Greater contact irritancy was seen from mixed oils of LC and LS than with other mixed oils. Mixtures of LC and LS at 0.075% showed the highest synergistic action (65.5% escaped) compared to that with unmixed oil alone at the same concentration (LC/20% and LS=32.2%). In addition, mixtures of LC and LS at 0.075% demonstrated the highest non-contact repellency (62.7%) and showed a greater effect than the use of LC (20%) or LS (20.3%) alone. We conclude that mixtures of two essential oils show potential as active ingredients for mosquito repellents.