Abstract
A foliage contact herbicidal substance was separated from ethyl ether fraction in n-hexane extract of Saussurea lappa roots and identified as dehydrocostus lactone [(3aS,6aR,9aR,9bS)-3,6,9-trimethylidene-3a,4,5,6a,7,8,9a,9b-octahydroazuleno[5,4-d]furan-2-one](DHCL). When DHCL at 4,000 ppm was foliage-applied to two grasses and two broadleaf plants, greater than 85% necrotic injury was obtained from large crabgrass, maize and soybean, whereas only about 40% necrotic injury appeared in black nightshade, indicating that DHCL has no gross morphological selectivity, but shows difference in contact response among the plant species tested. Conductivity in incubation medium of the leaf disks treated with DHCL increased as the incubation time continued. Relatively low contact injury in black nightshade as compared with the other three plant species tested was attributed to decrease in absorption of DHCL due to relatively high amount of cuticle. DHCL did not require light in the herbicidal action and there were no inhibitory effects on seed germination and cell elongation. Acetyl-CoA carboxylase activity was inhibited by 30% and 58% at $100\;{\mu}M$ and $1000\;{\mu}M$ DHCL, respectively. These results suggested that the herbicidal action of DHCL was related with inhibition of fatty acid synthesis which in turn caused to weaken cell membrane integrity.
목향(Saussurea lappa) 뿌리 n-hexane 추출물의 ethyl ether 분획물로부터 경엽 살초 활성을 나타내는 물질로 dehydrocostus lactone (3aS,6aR,9aR,9bS)-3,6,9-trimethylidene-3a,4,5,6a,7,8,9a,9b-octahydroazuleno[5,4-d]furan-2-one)(DHCL)을 분리 동정하였다. DHCL 4,000ppm의 경엽처리 결과, 바랭이, 옥수수 및 콩에 대하여 85% 이상의 엽신 고사율을 보인 반면에 까마중에서는 약 40%의 저해율을 나타내어, 화본과 및 광엽식물 간 선택성 차이는 나타나지 않았으나, 검정식물 초종 간 반응성 차이를 나타내었다. 까마중에서의 반응성 차이는 다른 검정식물과 비교하여 까마중 잎의 비교적 높은 cuticle 함량에 의한 흡수량 감소 때문이었다. 광은 DHCL의 살초활성 발현과 관련이 없었으며, 종자 발아 및 세포 생장 억제 효과는 나타내지 않았다. DHCL 처리에 의한 엽절편의 전도도 증가 및 acetyl-CoA carboxylase의 활성 저해효과로부터 DHCL의 살초 활성 발현은 일정 부분 지방산 생합성 저해에 따른 세포막 약화에 의해 나타날 가능성이 있는 것으로 나타났다.
