A new phenyldihydronaphthalene type lignan in the root of Qingyang ginseng
Cynanchum otophyllum Schneid is a common folk medicine in the genus Cynanchum of Asclepiadaceae. It is a perennial herbaceous twining vine, mainly distributed in Yunnan, Sichuan, Guangxi, Xizang, Guizhou and other provinces in China. The main medicinal parts of Qingyang ginseng are the rhizome. It has a pungent and sweet taste, a warm nature, and certain toxicity. It can dispel wind and dampness, benefit the kidneys, spleen, and stomach. The Qingyang Ginseng Tablets, which have been launched, have the effects of calming the liver and tonifying the kidneys, relieving phlegm and spasms. They are mainly used for symptoms such as epilepsy, dizziness, headache, vertigo, tinnitus, and soreness and weakness of the waist and knees. Research has shown that the dried roots of Qingyang ginseng have anti epileptic, anti depressive, immune regulatory, anti hepatitis, and anti Meniere syndrome effects. The chemical composition and structural types of Qingyang ginseng are diverse, mainly including C21 steroids and deoxyoligosaccharides. Among them, C21 steroids are considered as the characteristic substances and main pharmacological components of Qingyang ginseng. Modern pharmacological studies have shown that C21 steroidal compounds derived from plants in the Asclepiadaceae family have rich biological activities, such as anti-tumor, anti-inflammatory, antifungal, antiviral, etc. In recent years, natural C21 steroidal glycosides derived from the Asclepiadaceae family have shown significant anti-tumor activity and have potential research value. Qingyang ginseng is a traditional folk medicine in China, with abundant resources. However, most of the current research on its chemical composition is based on C21 steroids, and there is a lack of research on other types of components. Recently, our research group has studied the chemical composition of acid hydrolysates from dried roots of Qingyang ginseng, and obtained a series of C21 steroid glycosides with novel structures and significant anti-tumor activity. However, during the research process, we found some trace amounts of other types of components in its acid hydrolysate. Therefore, in order to further understand the material basis of traditional Chinese medicine Qingyang ginseng and improve its comprehensive resource utilization efficiency, this article isolated, purified, and structurally identified other types of components from the acid hydrolysate of Qingyang ginseng dried roots, and tested the cytotoxic activity of the isolated compounds, in order to discover novel anti-tumor lead compounds with novel structures.

Due to the fact that most of the research on the chemical composition of traditional Chinese medicine Qingyang Shen by domestic and foreign scholars has focused on C21 steroid glycosides, the study of its secondary glycosides, aglycones, or other types of components has been neglected, which to some extent limits its resource reuse and development. For the abundant and diverse sugar chain steroidal glycosides, scholars at home and abroad have focused on studying their secondary glycosides or aglycones, such as Tongguangteng, Xuchangqing, Baishouwu, and Black Eel Vine, mainly using acid catalyzed hydrolysis methods to obtain a series of bioactive secondary glycosides or steroidal aglycones. Based on successful literature precedents, our research group used acid hydrolysis catalysis to treat the 95% ethanol extract of Qingyang ginseng roots in the early stage, and isolated and identified a series of structurally novel and anti-tumor activity C21 steroid glycosides from it. In addition, we found that there are still trace amounts of other types of components in the acid hydrolysate of Qingyang ginseng roots. This experiment used modern chromatographic methods to separate and identify other types of components in the acid hydrolysate of Qingyang ginseng roots. Four lignans were discovered, among which compound 1 is a new phenyldihydronaphthalene type lignan. Further MTT experiments showed that compounds 2 and 3 have a certain degree of cytotoxic activity, especially against liver cancer HepG2 cells, with IC50 values of 34.19 ± 5.44 and 22.52 ± 9.13 μ M, respectively. Therefore, the four lignans obtained in this experiment were all discovered for the first time from plants of this genus. Although they may be deglycosylated derivatives produced by acid catalyzed hydrolysis of natural products, they reflect to some extent the presence of lignans in Qingyang ginseng plants, enriching their chemical structure types and providing a theoretical basis for the resource utilization of Qingyang ginseng, as well as new ideas and assistance for the search for new bioactive natural products.