Carbazole alkaloids from the peels of Clausena lansium

Antimicrobial activity of natural and semi-synthetic carbazole alkaloids

Since the first natural carbazole alkaloid, murrayanine, was isolated from Mwraya Spreng, carbazole alkaloid derivatives have been widely concerned for their anti-tumor, anti-viral and anti-bacterial activities. In recent decades, a growing body of data suggest that carbazole alkaloids and their derivatives have different biological activities. This is the first comprehensive description of the antifungal and antibacterial activities of carbazole alkaloids in the past decade (2012-2022), including natural and partially synthesized carbazole alkaloids in the past decade. Finally, the challenges and problems faced by this kind of alkaloids are summarized. This paper will be helpful for further exploration of this kind of alkaloids.

The primary neurotoxic factor, Lansamide I, from Clausena lansium fruits and metabolic dysfunction invoked

Wampee (Clausena lansium) is a common fruit in South Asia. The pulp is a tasty food, and the seed is a typical traditional herb in China. However, we identified a primary toxic compound, Lansamide I, by NMR and X-ray diffraction of single-crystal. The compound occurred at 4.17 ± 0.16 mg/kg of dried seed and 0.08 ± 0.01 g/kg of fresh fruit. In our phenotype-based toxicity investigation, the compound caused decreased hatchability of zebrafish eggs, increased malformations such as enlarged yolk sacs and pericardial edema, and delayed body length development. Moreover, the compound also caused nerve cell damage and decreased locomotor activity. The compound caused an increase in peroxidation levels in vivo, with increases in both malondialdehyde and superoxide dismutase levels, but did not interfere with acetylcholinesterase levels. Metabolomic studies found that the compound caused significant up-regulation of 16 metabolites, mainly amino acids and peptides, which were involved in the nucleotide metabolism pathway and the betaine biosynthesis module. The qRT-PCR revealed that the substance interfered with the mRNA expression of tat and dctpp. These discoveries offer fresh perspectives on the toxicity mechanisms and metabolic response to the primary harmful molecules in wampee, which could inform the rational usage of wampee resources.

Comprehensive Review of Phytochemical Profiles and Health-Promoting Effects of Different Portions of Wampee (Clausena lansium)

Clausena lansium, commonly known as wampee, is a subtropical fruit from the Rutaceae family characterized by its high nutrient content and numerous bioactive substances. This low-fat fruit is abundant in fiber, vitamins, minerals, and essential amino acids. Wampee has been found to contain several bioactive compounds, including essential oils, phenolic compounds, and alkaloids. These bioactive constituents provide numerous health-enhancing properties, such as antioxidant, neuroprotective, anticarcinogenic, anti-inflammatory, hepatoprotective, antidiabetic, and antimicrobial effects. The relationship between these compounds and their impacts on health has been explored in various studies. While the disease-prevention efficacy of C. lansium has been established, additional research is necessary to elucidate the precise mechanisms and metabolic pathways involved. This paper presents a comprehensive review of wampee, focusing on its bioactive compounds, the beneficial effects derived from its consumption, and the evidence supporting the development of wampee-based functional foods in future studies.

Antifungal active ingredient from the twigs and leaves of Clausena lansium Lour. Skeels (Rutaceae)

Two novel amides, named clauphenamides A and B, and twelve other known compounds were isolated from the twigs and leaves of Clausena lansium Lour. Skeels (Rutaceae). Their structures were elucidated on the basis of extensive spectroscopic analysis and comparison with data reported in the literature. Clauphenamide A (1) featured in the unit of N-2-(4,8-dimethoxyfuro [2,3-b]quinolin-7-yl)vinyl, and clauphenamide B (2) was a unprecedented N-phenethyl cinnamide dimer. Other known compounds belong to pyrrolidone amides (3 and 4), furacoumarins (7-10), simple coumarins (11-14), lignan (5) and sesquiterpene (6). Compounds 5, 6, 10 and 12 were separated from the genus (Clausena) for the first time, while 13 was isolated in the species (C. lansium) for the first time. The antifungal activities of the isolated compounds were assayed. As a result, at the concentration of 100 μg/ml, compared with the control (chlorothalonil, inhibition rate of 83.67%), compounds 1 and 2 were found to exhibit moderate antifungal activity against B. dothidea with inhibition rates of 68.39% and 52.05%, respectively. Compounds 11-14 also exhibited moderate activity against B. dothidea and F. oxysporum, with inhibition rates greater than 40%. In addition, compared with the control (chlorothalonil, inhibition rate of 69.02%), compounds 11-14 showed strong antifungal activity to P. oryzae, with inhibition rates greater than 55%. Among them, compound 14 has the strongest antifungal activity against P. oryzae, and the inhibition rate (65.44%) is close to that of the control chlorothalonil. Additionally, the structure-activity relationships of the separated compounds are also discussed preliminarily in this paper.

Fruit Peels: Food Waste as a Valuable Source of Bioactive Natural Products for Drug Discovery

Fruits along with vegetables are crucial for a balanced diet. These not only have delicious flavors but are also reported to decrease the risk of contracting various chronic diseases. Fruit by-products are produced in huge quantity during industrial processing and constitute a serious issue because they may pose a harmful risk to the environment. The proposal of employing fruit by-products, particularly fruit peels, has gradually attained popularity because scientists found that in many instances peels displayed better biological and pharmacological applications than other sections of the fruit. The aim of this review is to highlight the importance of fruit peel extracts and natural products obtained in food industries along with their other potential biological applications.

Total Synthesis of the Natural Carbazoles O-Demethylmurrayanine and Murrastanine A, and of a C4,C4′ Symmetric Murrastanine A Dimer from N-Phenyl-4,5-dimethylene-1,3-oxazolidin-2-one

The synthesis of natural carbazoles O-demethylmurrayanine and murrastanine A starting from the title exo-heterocyclic diene­ is described. In the synthesis of murrastanine A, its symmetric C4,C4′ dimer can be obtained as the sole product under rather mild conditions. In all cases, the key intermediate is the same diarylamine. The carbazole nucleus is obtained through a Pd-promoted cyclization of the appropriate diarylamine. For the synthesis of O-demethylmurrayanine, the cyclization takes place on a silylated derivative. The crystal structures of murrayanine, two diarylamines, and two non-natural carbazole intermediates are also presented.

Synthesis of Carbazoles by a Diverted Bischler-Napieralski Cascade Reaction

An unforeseen twist in a seemingly trivial Bischler–Napieralski reaction led to the selective formation of an unexpected carbazole product. The reaction proved to be general, providing access to a range of diversely substituted carbazoles from readily available substrates. Judicious variation of substituents revealed a complex cascade mechanism comprising no less than 10 elementary steps, that could be diverted in multiple ways toward various other carbazole derivatives.

A new benzofuran glycoside from the fruit of Clausena lansium

In this work, we isolated a new benzofuran glycoside, 6-β-d-glucosyl-6,7-dihydroxy-5-benzofuranpropanoic acid methyl ester (1), together with six known compounds (2-7) from the fruits of Clausena lansium (Lour.) Skeels. Extensive spectroscopic methods were employed to elucidate their structures. Herein, compounds 2, 3, 5 and 6 were reported from Clausena lansium (Lour.) Skeels for the first time. Moreover, compounds 1, 2, 4 and 6 showed comparable 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity to l-ascorbic acid, and compound 4 also exhibited potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP). All of the compounds showed oxygen radical absorbance capacity (ORAC) values ranging from 0.3 to 3.6 μmol trolex equivalent/μmol. In addition, compounds 3 and 5 also demonstrated good α-amylase inhibitory activity.

The sesquiterpenes from the stem and leaf of Clausena lansium with their potential antibacterial activities

Two new C₁₃-norsesquiterpenes claulanterpene A (1) and B (2), together with two known sesquiterpenes (3-4), were isolated from methanol extract of the stem and leaf of Clausena lansium collected from Qingyuan county, Guangdong Province, China. Their structures were elucidated on the base of extensive spectroscopic analysis and comparison with data reported in the literature. Among them, compound 4 showed antibacterial activity against Bacillus cereus.

Bioactive prenylated coumarins as potential anti-inflammatory and anti-HIV agents from Clausena lenis

The phytochemical study on the stems of Clausena lenis resulted in the isolation of three new prenylated coumarins, clauselenins A-C (1-3), together with nine known prenylated coumarins (4-12). The chemical structures of new prenylated coumarins (1-3) were elucidated by means of comprehensive spectral analyses and the known compounds (4-12) were determined by means of comparing their experimental spectral data with those described data in the literatures. All isolated prenylated coumarins were assessed for their anti-inflammatory effects together with anti-HIV activities in vitro. Prenylated coumarins 1-12 displayed remarkable inhibitory effects against nitric oxide (NO) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells in vitro with the IC₅₀ values which are comparable to hydrocortisone. Meanwhile, prenylated coumarins 1-12 exhibited considerable anti-HIV-1 reverse transcriptase (RT) activities possessing EC₅₀ values in the range of 0.17-9.08 µM. These findings indicate that the isolation and identification of these prenylated coumarins with pronounced anti-inflammatory effects as well as anti-HIV activities separated from the stems of C. lenis could be of great significance to the development of new anti-inflammatory and anti-HIV agents and their potential applications in the pharmaceutical industry.

Phytochemical Study of Stem and Leaf of Clausena lansium

Clausena lansium Lour. Skeels (Rutaceae) is widely distributed in South China and has historically been used as a traditional medicine in local healthcare systems. Although the characteristic components (carbazole alkaloids and coumarins) of C. lansium have been found to possess a wide variety of biological activities, little attention has been paid toward the other components of this plant. In the current study, phytochemical analysis of isolates from a water-soluble stem and leaf extract of C. lansium led to the identification of 12 compounds, including five aromatic glycosides, four sesquiterpene glycosides, two dihydrofuranocoumarin glycosides, and one adenosine. All compounds were isolated for the first time from the genus Clausena, including a new aromatic glycoside (1), a new dihydrofuranocoumarin glycoside (6), and two new sesquiterpene glycosides (8 and 9). The phytochemical structures of the isolates were elucidated using spectroscopic analyses including NMR and MS. The existence of these compounds demonstrates the taxonomic significance of C. lansium in the genus Clausena and suggests that some glycosides from this plant probably play a role in the anticancer activity of C. lansium to some extent.

Carbazole Alkaloids with Potential Neuroprotective Activities from the Fruits of Clausena lansium

Clausena lansium, also known as wampee, is a species of strongly scented evergreen trees belonging to the genus Clausena (Rutaceae), which is native to southern China. Its ripe fruits have been consumed as a very popular fruit and reported to possess a range of biological activities. To study the potential health-promoting constituents from the fruits of C. lansium, a chemical investigation on its fruits was thus carried out. In this study, 16 carbazole alkaloids (1-16), including six new carbazole alkaloids, clausenalansines A-F (1-6), were separated from the fruits of C. lansium. The molecular structures of these isolated new carbazole alkaloids (1-6) were ambiguously established on the basis of comprehensive spectroscopic methods. The known analogues (7-16) were determined via comparing their experimental data with those described in the literature, which were separated from C. lansium for the first time. All these isolated alkaloids were tested in vitro for their neuroprotective effects against 6-hydroxydopamine induced cell death in human neuroblastoma SH-SY5Y cells. Carbazole alkaloids 1-16 displayed remarkable neuroprotective effects possessing the EC₅₀ values ranging from 0.36 ± 0.02 to 10.69 ± 0.15 μM. These findings indicate that regular consumption of the fruits of C. lansium may help people prevent the occurrence of Parkinson's disease. In addition, the separation and identification of these carbazole alkaloids possessing remarkable neuroprotective effects from the fruits of C. lansium could be extremely important to the discovery of new agents for the prevention and treatment of Parkinson's disease.

Design, synthesis, docking study, α-glucosidase inhibition, and cytotoxic activities of acridine linked to thioacetamides as novel agents in treatment of type 2 diabetes

A novel series of acridine linked to thioacetamides 9a-o were synthesized and evaluated for their α-glucosidase inhibitory and cytotoxic activities. All the synthesized compounds exhibited excellent α-glucosidase inhibitory activity in the range of IC₅₀ = 80.0 ± 2.0-383.1 ± 2.0 µM against yeast α-glucosidase, when compared to the standard drug acarbose (IC₅₀ = 750.0 ± 1.5 µM). Among the synthesized compounds, 2-((6-chloro-2-methoxyacridin-9-yl)thio)-N-(p-tolyl) acetamide 9b displayed the highest α-glucosidase inhibitory activity (IC₅₀ = 80.0 ± 2.0 μM). The in vitro cytotoxic assay of compounds 9a-o against MCF-7 cell line revealed that only the compounds 9d, 9c, and 9n exhibited cytotoxic activity. Cytotoxic compounds 9d, 9c, and 9n did not show cytotoxic activity against the normal human cell lines HDF. Kinetic study revealed that the most potent compound 9b is a competitive inhibitor with a K_i of 85 μM. Furthermore, the interaction modes of the most potent compounds 9b and 9f with α-glucosidase were evaluated through the molecular docking studies.

Bioactive Compounds from the Stems of Clausena lansium

In view of the significant neuroprotective effect of Clausena lansium, we continued to separate the n-butanol and the water extracts from the stems of C. lansium in order to find the leading compounds with significant activity. Two new phenolic glycosides, Clausenolside A-B (1-2), one new pair of phenolic enantiomers (3a, 3b), and two new monoterpenoids, clausenapene A-B (4-5), together with twelve known analogues (6-17) were isolated from the stems of C. lansium. Compounds 1-17 were obtained from C. lansium for the first time. Compounds 3a, 3b, 4, 16, and 17 showed strong or moderate potential neuroprotective effects on inhibited PC12 cell injury induced by okadaic acid, and compound 9 exhibited strong potential hepatoprotective activities. Their structures were elucidated on the basis of spectroscopic analyses, including UV, IR, NMR experiments, and electronic circular dichroism (ECD) spectra.

A new apotirucallane-type triterpenoid from Atalantia buxifolia

A new triterpenoid (1) with apotirucallane skeleton was isolated from the ethanol extract of the roots of Atalantia buxifolia (Poir.) Oliv. The complete structural assignment of the new compound was elucidated by a combination of 1D, 2D NMR (HMQC, HMBC, COSY, and NOESY), and HR-ESI-MS analysis. Moreover, this new compound was evaluated in vitro for its cytotoxic, antimicrobial and enzymes inhibitory activities.