Two new lignans in Rhododendron grandiflorum
Rhododendron minutiflorum, also known as slender rhododendron or slender pomegranate flower, is a plant of Rhododendron L. in the Rhododendron family. It is commonly found in hilly areas at an altitude of 1120-1430m and is mainly produced in Guangxi and Guangdong provinces in China. Many plants in this genus have high medicinal and economic value, such as R. molle, which has anti-inflammatory and analgesic pharmacological effects and can be used for the treatment of diseases such as rheumatoid arthritis and cardiovascular disease; R. athopogonoide, a commonly used Tibetan medicine, has the effects of relieving cough and asthma, clearing heat and detoxifying. With the rapid development of modern chromatographic separation and spectroscopic techniques, research on the chemical composition and pharmacological activity of Rhododendron plants is constantly deepening and systematized both domestically and internationally. In recent years, many structurally novel and highly active chemical compounds have been isolated from plants of this genus, including coumarins, lignans, flavonoids, and terpenes. Many compounds exhibit significant biological activities such as hypoglycemic, anti-tumor, anti-inflammatory, antibacterial, insecticidal, and antioxidant properties.

The hypoglycemic activity of Rhododendron plants has always been of great concern to researchers both domestically and internationally. Choi et al. from R Rhododendron acid A and ursolic acid isolated from brachycarpum exhibit strong inhibitory activity against the key insulin signaling enzyme PTP1B, with IC50 values of (6.3 ± 0.6) and (3.1 ± 0.3) μ mol/L, respectively. Liao et al. from R A pair of enantiomers (-) – rhodonoids B and (+) – rhodonoids B with PTP1B inhibitory activity were isolated from Capitalum, with IC50 values of (43.56 ± 8.53) and (30.38 ± 13.41) μ mol/L, respectively. From R The 3-O-acetyllursorolic acid isolated from arboreum exhibited significant inhibitory activity against alpha glucosidase, with an IC50 value of 3.3 ± 0.1 μ mol/L. Muhammad et al. discovered R The ethyl acetate and dichloromethane extracts of 80% methanol crude extract from Schlippenbachii bark can effectively inhibit α – glucosidase activity and reduce blood glucose concentration in mice.

Xiaohua Rhododendron belongs to the Rhododendron genus, and there are currently no reports on the chemical composition and pharmacological activity of Xiaohua Rhododendron both domestically and internationally. In view of this, this article studied the chemical composition of the ethyl acetate extract of the 95% ethanol extract of Rhododendron simsii and screened the α – glucosidase inhibitory activity of the isolated monomer compounds, in order to provide reference and scientific basis for the further development and utilization of Rhododendron simsii.

This experiment studied the chemical composition and in vitro α – glucosidase inhibitory activity of 95% ethanol extract of Rhododendron simsii. Nine compounds were isolated and identified, including lignans, flavonoids, and phenolic compounds. Among them, compound 1 is a relatively rare benzofuran type lignan in natural products, compound 2 is a new phenyldihydronaphthalene type lignan, and the remaining compounds are all isolated from Rhododendron simsii for the first time. The PNPG method was used to test the α – glucosidase inhibitory activity of the remaining 8 compounds except for compound 2. The results showed that compounds 8 and 9 had good α – glucosidase inhibitory activity, and the conclusions obtained from the experiment were similar to those reported in other research literature. Therefore, it is speculated that apigenin and kaempferol are important material bases for the in vitro hypoglycemic activity of Rhododendron simsii. This experiment conducted the first study on the chemical composition and α – glucosidase inhibitory activity of Rhododendron fortunei, providing a reference for the rational development and utilization of its plant chemical resources.