Bio-pesticidal and Antimicrobial Coumarins from Angelica dahurica (Fisch. Ex Hoffm)

Angelica dahurica is an important traditional Chinese herb which is widely used in curing acne, ulcers, carbuncles, rheumatism, headaches and toothaches. A systematic antifungal bioassay-guided fractionation of the ethyl acetate extract from A. dahurica led to the isolation of six coumarins, namely, suberosin, bergapten, alloimperatorin, xanthotoxol, 5-methoxy-8-hydroxypsoralen and pabulenol. These coumarins were subsequently subjected to evaluation for antifungal, antibacterial, antimalarial and antileishmanial activities. Bergapten and xanthotoxol showed good antifungal activity against Phomopsis viticola, with 99.8% and 73.0% fungal growth inhibition at the concentration of 30 µM and compared with the positive control. Among all the compounds tested against Phomopsis obscurans, bergapten and suberosin showed the highest antifungal activity with 61.0% and 88.3% inhibition, respectively, at 30 µM concentration. 5-Methoxy-8-hydroxypsoralen displayed toxicity against Streptococcus iniae with IC(50) and MIC values of 11.6 ± 0 and 2.32 ± 0 mg/L. Suberosin and alloimperatorin displayed moderate activity against Leishmania donovani promastigotes with IC(50) of 4.43 µg/mL and 20.43 µg/mL. Essential oil and water extracts showed larvicidal activity in 1-d old Ae. Aegypti, whereas there was no activity with petroleum ether, ethyl acetate and butanol extracts. Among the pure compounds, only bergapten showed larval mortality. Essential oil and extracts of Angelica dahurica showed very weak biting deterrent activity as compared to the positive control DEET. This is the first report of the following: 1) antifungal activity of suberosin against Phomopsis obscurans and of alloimperoitrin against Phomopsis viticola; 2) antileishmanial activity of suberosin and alloimperatorin; and 3) 5-methoxy-8-hydroxypsoralen antibacterial activity against the freshwater fish pathogen S. iniae.