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Background Clausena lansium (Lour.) Skeels, belonging to the genus Clausena of the family Rutaceae, has a wide range of medical and agricultural activities. Previous studies on agricultural activities have shown that C. lansium extracts and some components have obvious herbicidal activities. In order to study systematically herbicidal activity of this plant, we studied the herbicidal effect of ethyl acetate (EtOAc) extract from the stems and leaves of this plant and further isolated the active compounds. Results The EtOAc extract inhibited the growth of roots and shoots of Echinochloa crus-galli (L.) Beauv., and the inhibitory effect of the EtOAc extract on roots were stronger than those on shoots with half maximal inhibitory concentration (IC50 ) values of 420.45 and 585.05 mg L-1 , respectively. Fifteen compounds were subsequently isolated and identified from the stems and leaves of C. lansium, including nine O-monoterpenoid furanocoumarins and six cinnamamides. Our results showed that most compounds exhibited varying degrees of herbicidal activities to E. crus-galli. Among them, compounds 3, 8, and 13-15 showed the best inhibitory activities on the growth of E. crus-galli roots, with inhibition rate values ranging from 70% to 83% at a concentration of 300 mg L-1 . Compounds 1 and 2 are two new compounds, and their structures were established as 5-O-monoterpenoid furanocoumarin and 8-O-monoterpenoid furanocoumarin, and named as claulansicoumarin-A and -B, respectively. Conclusion The EtOAc extract and pure compounds showed noticeable herbicidal activities against E. crus-galli and indicated a great potential for these natural compounds to be developed as a herbicide. © 2020 Society of Chemical Industry.

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.

Two new oleanane derivatives, leonuronins A and B (1 and 2), along with three known oleanane triterpenes (3–5) were isolated from the fruits of Leonurus japonicus. Their structures were elucidated on the basis of NMR, MS, IR and UV spectroscopic data. The new compounds were tested for cytotoxic activities against A549 and Hela cancer cell lines. Compounds 1 and 2 exhibited weak cytotoxicity with IC50 values ranging from 6.97 to 18.13 μM.

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.

Phytochemical analysis of isolates from the aerial parts of Clausena lansium Lour. Skeels (Rutaceae) led to the identification of 14 alkaloids, including two indole alkaloids (1 and 2), one quinoline alkaloid (3), two pyridine alkaloids (4 and 5), four carbazole alkaloids (6–9) and five amides alkaloids (10–14). The phytochemical structures of the alkaloids were established by means of NMR and MS spectral analyses. Compounds (4, 5, 14) were three new natural products, while 1–3 and 10 were firstly reported from the genus Clausena and 8 and 9 were isolated from this species for the first time. The chemotaxonomic significance of these isolated alkaloids has also been discussed. All the isolated alkaloids were tested for their cytotoxic activity against Hela cancer cell line. Among them, four carbazole alkaloids 6–9 exhibited weak cytotoxicity with IC50 values ranging from 69.31 to 138.32 μM.

The present study carried out a phytochemical investigation of the methanol extract of the branches and leaves of Clausena lansium and afforded nine carbazole alkaloids (compounds 1-9) including two new carbazole alkaloids, claulansiums A and B (compounds 1 and 2). The new compounds were elucidated on the basis of extensive spectroscopic data (MS, NMR, IR, and UV) and the known compounds were identified by comparing spectroscopic data with those reported in literature. All the isolated compounds were tested for their cytotoxic activity against A549 and Hela cancer cell lines. Our results showed that compounds 2-6 exhibited varying degrees of cytotoxicity to cancer cells, with IC50 values ranging from 8.67 to 98.89 μmol·L-1.