Larvicidal activity of the essential oil from Tetradium glabrifolium fruits and its constituents against Aedes albopictus

BACKGROUND

In our screening programme for new agrochemicals from wild plants, the essential oil of Tetradium glabrifolium (Champ. ex Benth.) T.G. Hartley fruits was found to possess strong larvicidal activity against the Asian tiger mosquito, Aedes albopictus L. The essential oil was extracted via hydrodistillation, and the constituents were determined by GC-MS analysis. The active compounds were isolated and identified by bioassay-directed fractionation.

RESULTS

GC-MS analyses revealed the presence of 19 components with 2-tridecanone (43.38%), 2-undecanone (24.09%), D-limonene (13.01%), caryophyllene (5.04%) and β-elemene (4.07%) being the major constituents. Bioactivity-directed chromatographic separation of the oil led to the isolation of 2-tridecanone, 2-undecanone and D-limonene as active compounds. The essential oil of T. glabrifolium exhibited larvicidal activity against the early fourth-instar larvae of A. albopictus, with an LC50 value of 8.20 µg mL(-1). The isolated constituent compounds, 2-tridecanone, 2-undecanone and D-limonene, possessed strong larvicidal activity against the early fourth-instar larvae of A. albopictus, with LC50 values of 2.86, 9.95 and 41.75 µg mL(-1) respectively.

CONCLUSION

The findings indicated that the essential oil of T. glabrifolium fruits and the three constituents have an excellent potential for use in control of A. albopictus larvae and could be useful in the search for newer, safer and more effective natural compounds as larvicides.

New phenylpropenoids, bis(1-phenylethyl)phenols, bisquinolinone alkaloid, and anti-inflammatory constituents from Zanthoxylum integrifoliolum

Five new compounds, including two new phenylpropenoids, (R,E)-1-[4-(3-hydroxyprop-1-enyl)phenoxy]-3-methylbutane-2,3-diol (1) and 4-hydroxy-3-(3-methyl-2-butenyl)cinnamyl alcohol (2), two new bis(1-phenylethyl)phenols, 2,6-bis(1-phenylethyl)phenol (3) and 2,4-bis(1-phenylethyl)phenol (4), and a new bisquinolinone alkaloid, 18-demethylparaensidimerin C (5), together with 17 known compounds have been isolated from the stem wood of Zanthoxylum integrifoliolum. The structures of these new compounds were determined through spectral analyses including extensive 2D nuclear magnetic resonance data. Among the isolates, N-methylflindersine (7), (-)-simulanol (10), and evofolin-C (16) exhibited potent inhibition against N-formylmethionylleucylphenylalanine-induced superoxide production with IC(50) values less than 12 microM.

Prenylated phenylpropenes from Coleonema pulchellum with antimicrobial activity

The lipophilic root extract of Coleonema pulchellum was analysed and tested for antifungal and antibacterial activity. Eight previously undescribed prenyloxy and geranyloxy phenylpropenes, were isolated as major compounds together with the known evofolin-C as well as the lignans (+/-)-sesamin and (+/-)-prenylpiperitol, the diterpene (-)-pimara-9(11),15-dien-19-oic acid and the 2,4-decadienoic acid isobutylamide. All structures were established by spectroscopic evidence. From the new phenylpropenes, named evofolin-C-acetate, colenemol, colenemal, prenycol acetate, dehydroprenycol acetate, precolpuchol, colpuchol and colpuchol acetate, the dihydroxylated precolpuchol displayed the strongest antifungal and antibacterial activity against Cladosporium herbarum and Staphylococcus aureus, respectively.