Study on the diterpenoid components and biological activities in the stem of Thunder God Vine
Tripterygium wilfordii Hook. f. is a plant of the genus Tripterygium, also known as water grass, intestinal grass, etc. It is mainly distributed in the southern and southwestern regions of the Yangtze River Basin. Thunder God Vine was first recorded in the “Shennong Bencao Jing”. It has a bitter and pungent taste, a cold nature, and belongs to the liver and kidney meridians. It has the effects of dispelling wind and dampness, killing insects and detoxifying, reducing swelling and pain, and relaxing tendons and activating collaterals. As a commonly used traditional Chinese medicine, Tripterygium wilfordii often uses its roots as medicine. It has been developed into various Tripterygium wilfordii preparations, such as Tripterygium wilfordii polysaccharide tablets, Tripterygium wilfordii tablets, Tripterygium wilfordii total terpenoids tablets, and Tripterygium wilfordii double layered tablets. These Tripterygium wilfordii preparations are mainly used for the treatment of immune and inflammatory diseases, such as rheumatoid arthritis, lupus erythematosus, and ulcerative colitis. In addition, modern pharmacological research has found that Tripterygium wilfordii also has anti-tumor activity, and it has great application prospects in tumor treatment.

So far, domestic and foreign researchers have isolated and identified more than 500 compounds from the genus Tripterygium wilfordii, mainly including diterpenes, triterpenes, and sesquiterpenes. Among them, diterpenes have diverse skeleton types, including rosin type, sea pine type, enantiosaurine type, and other types. Rosin type ternary epoxy diterpenoid lactones, such as Triptolide and its derivatives, have long been considered the main active ingredients in the anti-inflammatory and anti-tumor properties of Triptolide diterpenoids. However, the low content of Tripterygium wilfordii Hook. f. and its derivatives, and the strong liver and kidney toxicity of most of them, greatly limit the application and development of Tripterygium wilfordii Hook. f. It is worth further studying whether there are other low toxicity and high efficiency anti-inflammatory and anti-tumor active diterpenoids in Tripterygium wilfordii, apart from Triptolide and its derivatives. On the other hand, research on the chemical composition of Tripterygium wilfordii mainly focuses on its main medicinal parts, the roots, and the study of the chemical composition of its stems is not deep enough. Literature review has found that a total of 24 compounds have been isolated from the stems or mixed extracts of stems and leaves of Tripterygium wilfordii, including 9 diterpenoid compounds. In view of this, various chromatographic and spectroscopic techniques were used in this study to systematically isolate and identify the diterpenoid components in the stem of Tripterygium wilfordii, and the isolated compounds were evaluated for their in vitro anti-inflammatory and anti-tumor activities.

In this experiment, 20 diterpenoid compounds were isolated and identified from the ethyl acetate extraction phase of the ethanol extract of the stem of Tripterygium wilfordii. The skeleton types include diterpenoid quinones, abietane type, sophocarpine type, and enantiosaurine type. Among them, 1 is a new diterpenoid quinone compound, and compounds 10, 19, and 20 were isolated from Tripterygium wilfordii for the first time. Based on previous research, this further enriches the research content of the chemical composition of Tripterygium wilfordii. We did not isolate rosin alkyl diterpenoid lactones with a ternary epoxy structure, possibly because these compounds are mainly distributed in the roots and have a lower content in the stems. Compounds 1-20 were screened for their in vitro anti-inflammatory and anti-tumor activities, and compounds 2, 3, and 20 showed significant anti-inflammatory activity. 2 is a rosin type diterpene with a quinone structure in the C ring, and the quinone structure in the C ring may be a key active group for the anti-inflammatory properties of rosin type diterpenes. Previous studies have shown that rosin type diterpenoid lactones (such as Tripterygium wilfordii Hook. f. and its derivatives) with a ternary epoxy structure are the main active ingredients in the anti-inflammatory properties of diterpenoid compounds in Tripterygium wilfordii Hook. f. This study suggests that in addition to Tripterygium wilfordii Hook. f. and its derivatives, rosin type diterpenes with a C-ring quinone structure may also be one of the active ingredients in the anti-inflammatory properties of Tripterygium wilfordii Hook. f. diterpenes. The findings of this study provide new clues for our understanding of the anti-inflammatory substance basis of Tripterygium wilfordii, and also provide ideas for the structural modification of using rosin type diterpenes as anti-inflammatory lead compounds. In addition, none of the compounds showed significant anti-tumor activity, consistent with literature reports. Rosin alkyl diterpenoid lactones with a ternary epoxy structure may be the key active ingredient in the anti-tumor activity of Tripterygium wilfordii Hook. f.