Essential oils (EOs) have been shown to have a diversity of beneficial human health effects. Clausena is a large and highly diverse genus of plants with medicinal and cosmetic significance. The aim of this study was to analyze the composition of Clausena lansium EOs and to investigate their potential antifungal effects. The chemical compositions of Clausena lansium EOs obtained by hydrodistillation were analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 101 compounds were identified among the diverse extracts of C. lansium. EOs of leaves and pericarps from different cultivars (Hainan local wampee and chicken heart wampee) collected in Hainan (China) were classified into four clusters based on their compositions. These clusters showed different antifungal activities against five Candida species (C. albicans, C. tropicalis, C. glabrata, C. krusei and C. parapsilosis) using the disc diffusion method. Clausena lansium EOs of pericarps displayed noteworthy antifungal activitives against all the tested Candida strains with inhibition zone diameters in the range of 11.1–23.1 mm. EOs of leaves showed relatively low antifungal activities with inhibition zone diameters in the range of 6.5–22.2 mm. The rank order of antifungal activities among the four EO clusters was as follows: Cluster IV> Cluster III > Cluster I ≥ Cluster II. These results represent the first report about the correlation between chemical composition of C. lansium EOs and antifungal activity. Higher contents of β-phellandrene, β-sesquiphellandrene and β-bisabolene in EOs of pericarps were likely responsible for the high antifungal activity of Cluster IV EOs. Taken together, our results demonstrate the chemical diversity of Clausena lansium EOs and their potential as novel antifungal agents for candidiasis caused by Candida spp. Furthermore, the obtained results showing a wide spectrum of antifungal activities provide scientific evidence for the traditional use of these plants.

Infections caused by Candida albicans (C. albicans) and increasing resistance to commonly used drugs lead to a variety of mucosal diseases and systemic infectious diseases. We previously confirmed that the essential oil of Clausena lansium (Lour.) Skeels seeds (CSEO) had antifungal activity against C. albicans, but the detailed mechanism between the chemical components and antifungal activity is unclear. In this study, a quantitative analysis of five volatile components of CSEO, including sabinene, α-phellandrene, β-phellandrene, 4-terpineol, and β-caryophyllene, was carried out using the gas chromatography–mass spectrometry (GC–MS) method. Both the broth dilution and kinetic growth methods proved that the antifungal activity of CSEO against fluconazole-resistant C. albicans was better than that of its main components (sabinene and 4-terpineol). To further investigate the inhibitory mechanism, the transcriptional responses of C. albicans to CSEO, sabinene, and 4-terpineol treatment were determined based on RNA-seq. The Venn diagram and clustering analysis pattern of differential expression genes showed the mechanism of CSEO and 4-terpineol’s anti-C. albicans activity might be similar from the perspective of the genes. Functional enrichment analysis suggested that CSEO regulated adherence-, hyphae-, and biofilm-formation-related genes, which may be CSEO’s active mechanism of inhibiting the growth of fluconazole-resistant C. albicans. Overall, we preliminarily revealed the molecular mechanism between the chemical components and the antifungal activity of CSEO against C. albicans. This study provides new insights to overcome the azole resistance of C. albicans and promote the development and application of C. lansium (Lour.) Skeels seeds.

A rapid and sensitive ionic liquid (IL) based headspace gas chromatography-mass spectrometry (HS-GC-MS) method was developed for analyzing volatile components in leaf, pericarp, and seed of Clausena lansium from different areas in Hainan Province, China. HS efficiencies were carefully investigated by using three ILs and water as matrix media. Extraction parameters, including equilibrium temperature, equilibrium time, and stirring rate had been evaluated and optimized by using an orthogonal design with OA₉(3³) table. Under the optimized condition of IL-based HS-GC-MS, only 100 mg of sample and 2 mL of [Bmim][BF₄] were needed to comprehensively and accurately analyze the volatile components in Clausena lansium. By utilizing a cluster analysis, six clusters were obtained for ninety components. This method was simpler, more rapid, and more sensitive when compared with previously reported methods for analyzing and identifying volatile components in Clausena lansium. The results may provide a theoretical basis for further exploitation of Clausena lansium.

Streptococcus mutans is one of the most significant pathogens leading to dental caries by producing highly cariogenic biofilms within the oral cavity. However, the increasing antimicrobial resistance brings great difficulties to the prevention and treatment of dental caries. Therefore, it is very important to develop new and effective antimicrobial agents from natural sources. Clausena lansium (Lour.) Skeels, a plant commonly cultivated in Southern China, is rich in various active constituents. In this study, the main constituents of the essential oils extracted from Clausena lansium leaves (EOL), seeds (EOS), peels (EOP) were precisely analyzed by gas chromatography–mass spectrometry. The antimicrobial and anti-biofilm activities of EOL, EOS, and EOP, along with their main chemical constituents, against Streptococcus mutans were comprehensively evaluated. The primary constituent in EOL was β-caryophyllene, with a content of 112.29 mg/mL. EOS was found to be abundant in sabinene and 4-terpineol, with constituents of 147.21 mg/mL and 54.36 mg/mL, respectively. In EOP, the most predominant constituent was β-phellandrene, with a content of 173.95 mg/mL. The minimum inhibitory concentrations of EOL, EOS, and EOP were 0.12, 2.00, and 1.00 mg/mL, respectively. The minimum concentrations of inhibiting at least 90% biofilm formation of EOL, EOS, and EOP was 0.12 mg/mL, 2.00, and 2.00 mg/mL, respectively. Intriguingly, the antimicrobial and anti-biofilm efficacies of the main constituents were significantly lower than those of the essential oils. By observing the dynamic changes of the biofilm formation of S. mutans treated with essential oils, it was found that the process of biofilm formation was greatly delayed. In some cases, there was even no biofilm formation. The results of real-time quantitative PCR indicated that the expression levels of brpA, gtfB, gtfC, gtfD, and luxS genes were down-regulated after treatment with the essential oils. This study reinforces the potential of Clausena lansium as a promising source for developing new antimicrobial and anti-biofilm agents. They could inhibit the proliferation and virulence of S. mutans, thereby contributing to the control of dental caries.

Candida albicans is the most prominent conditional fungal pathogen, which can cause systemic candidiasis when an individual becomes immunocompromised. The widespread and long-term use of azoles like fluconazole (FLC) has led to a significant increase in drug resistance, posing substantial challenges to clinical treatment. In our previous study, benzyl isothiocyanate (BITC) was extracted from Carica papaya L. seed, and it exhibited a notable inhibitory effect against C. albicans. However, the application of BITC is restricted by its instability, poor water solubility, volatility, and easy degradation. This study aimed to prepare BITC-loaded nanostructured lipid carrier (BITC-NLC) to address these limitations of BITC and enhance antifungal efficacy in vitro and in vivo against C. albicans. The results of physicochemical properties showed that BITC-NLC had small particle size, good physical stability, and high encapsulation efficiency. In vitro, the antifungal effect of BITC-NLC was better than BITC against both sensitive and resistant C. albicans and better than FLC against resistant C. albicans. Moreover, in the in vivo experiment using systemic candidiasis mice model induced by resistant C. albicans, BITC-NLC was more remarkable than BITC and FLC in the increase of the survival rate and the splenic index, the reduction of the fungal burden, and the alleviation of the pathological damage. These findings may be attributed to the enhanced stability and sustained release of BITC. This study highlights the potential of BITC-NLC as a novel and effective formulation for the clinical treatment of drug-resistant C. albicans infections, thereby expanding the application scope of papaya.