Study on Chemical Components and Inhibition of NO Production Activity of Rhododendron yunnanensis
Rhododendron pachypodum Balf. f. et W. W. Sm is a member of the genus Rhododendron of the Rhododendron family, also known as Rhododendron undulata and white tofu pudding, which is distributed in most areas of southeast and southwest Yunnan. Rhododendron plants have the effects of clearing heat, detoxifying, promoting blood circulation, and stopping bleeding. In folk medicine, their roots and leaves are used as herbs for internal and external consumption; This genus of plants has a diverse range of chemical components and novel structures, mainly including terpenes, flavonoids, volatile oils, coumarins, phenols, and other chemical components. Among them, the grayannane type diterpenes are representative and have significant biological activities such as pain relief, anti-inflammatory, anti-tumor, and antiviral. Current research has shown that plants in the Rhododendron genus, such as Rhododendron fortunei, Rhododendron fragrans, Rhododendron scoparia, and Rhododendron grandiflorus, have complex chemical compositions and good anti-inflammatory activities. However, there is currently no research on the chemical composition and biological activity of Rhododendron yunnanensis, which is widely distributed in Yunnan. Therefore, in order to explore the chemical composition and biological activity of Rhododendron yunnanensis, this experiment isolated 26 compounds from the ethyl acetate extract of Rhododendron yunnanensis using a systematic separation method, and screened all compounds for in vitro anti-inflammatory activity. In order to clarify the anti-inflammatory substance basis of Rhododendron yunnanensis and provide theoretical basis for further development of its value.

Rhododendron is widely distributed and has abundant resources in Yunnan. Yunnan has 320 species of rhododendrons, including subspecies and varieties, accounting for 56% of China and 31% of the world. The custom of eating flowers in ethnic areas of Yunnan has a long history. Long term field practice has shown that the darker the color of azaleas, the more toxic they are. People usually only consume a small number of white and light colored azaleas, so white cloud azaleas also exist in the diet of Yunnan people. There are no research reports on the composition and activity of Rhododendron yunnanensis, as it is only distributed in some areas of Yunnan. To investigate the safety of Rhododendron yunnanensis as a vegetable flower and explore its anti-inflammatory components, our research group studied the chemical composition of Rhododendron yunnanensis and isolated 26 compounds as a result. Upon reviewing relevant literature, it was found that none of the compounds we reported had any reported anti-inflammatory activity. Therefore, screening for NO release inhibitory activity was conducted on some monomeric compounds, and it was found that compounds (2Z) -2,6-dimethyl-2,7-octadiene-1,6-diol (13), 4-O-methylcedarzine (16), and 6,8-di-C-methyldihydrokaempferol (18) can inhibit the release of NO in RAW 264.7 macrophages induced by LPS. Among them, compound 4-O-methylcedarzine showed significant anti-inflammatory activity, with an IC50 value of 33.5 ± 1.5 μ mol/L. In addition, three resveratrol type toxins (compounds 1-3) were isolated from Rhododendron yunnanensis in this study. The literature reports that these three compounds have significant analgesic activity. However, these compounds belong to the category of neurotoxins in the nervous and cardiac system, which can enhance myocardial contractility and induce rapid cardiac arrhythmias, leading to cardiac arrest and death. There are many reports from foreign researchers on the study of resveratrol, especially in some honey where the presence of this type of toxin can be detected. Therefore, further research is needed on the food safety of Rhododendron yunnanensis.