Primary Study On The Formation Mechanism Of Chemotype In Isodon Rubescens(Hemsl.)H. Hara

Donglingcao, Isodon rubescens (Hemsl.) Hara, is a Chinese medicinal plant of Isodon (previous Rabdosia), Lamiaceae (previous Labiatae). It is also known as Binglingcao, Liuyueling, Shanren in Chinese. It’s widely distributed in the Yellow River Valley and Yangtze River Valley in China, and among various mountains in Henan Province, especially in Jiyuan, Henan Taihang Mountain area. This herb has been long used as a folk remedy for the treatment of sore throat, cold in the head, bronchitis, chronic hepatitis, rheumatism and joint pain, Snake bites and so on. The crude preparations of the whole plant can relieve esophageal, gastric cardia, liver, breast and colorectal cancer patients, and prolong lives by clinical observation.Phytochemical studies of Isodon rubescens have revealed that it mainly contains diterpenoids, triterpenoids, sterols, flavonoids, phenolic acids and volatile oils, as well as other chemicals, of which diterpenoids are studies for most and also the main active ingredients. Oridonin and OGP-46are the two main diterpenoid ingredients isolated from this plant, and have significant pharmacological activity. Reseach group of our school had found that some plant Individuals or population in Jiyuan contain Oridonin, but not OGP-46, while others are just the opposite. However, those two types can’t be identified from the appearance. Plant that is divided for several types by differences in chemical composition is known as chemotypes, which are intraspecific variations due to significant difference of plant secondary metabolites. Chemotypes can be often found in plants, especially in medicinal plant such as mint, patchouli, camphor, and so on.Firstly, High Performance Liquid Chromatography (HPLC) was employed to veritify the characteristic component in the samples collected in Jiyuanin (except one in Zhengzhou).The results showed that the samples can be divided into two groups: the Oridonin group and the OGP-46group, just as what was predicted.Secondly, endophytes were isolated and purified from the roots, stems and leaves of7samples. In all,220endophytes were obtained, and then were fermented, the fermentation products were purified by the method of extraction. The extract was detected with pure Oridonin and OGP-46by TLC and HPLC. At last one cndophytic fungus producing Oridonin was isolated. It is inferred that this may be related to the difference.The rDNA ITS sequences between the samples were analysed, the result demonstrated that they were same to each other except two bases. The proportion (only0.3%) was so small that phylogenetic tree couldn’t be built by software. So this difference between the two chemotypes was not reflected in the ITS sequences. This may provide a reference for the research of the two chemotypes from the view of genetics.