Terpenoids and their anti-inflammatory activity in Guangdong purple pearls
Callicarpa kwangtungensis Chun. is a deciduous shrub of the Callicarpa L. genus in the family Verbenaceae. It is a representative medicinal plant of the genus and is commonly used as a medicinal herb in the Lingnan region, mainly distributed in Guangdong, Guangxi, Jiangxi, Hunan, and other places. This variety of medicinal materials is included in Volume I of the 2020 edition of the Chinese Pharmacopoeia. It has the effects of astringency, hemostasis, heat clearing and detoxification. It is commonly used to treat bleeding, hemoptysis, hematemesis, hematochezia, metrorrhagia, traumatic bleeding, cough due to lung heat, sore throat and hot toxic sores. It is the main raw material of the “anti inflammation” series of traditional Chinese patent medicines and simple preparations. In addition, Guangdong purple pearls can also be used for daily tea drinks in areas south of the Yangtze River. In recent years, members of our research group have conducted a relatively systematic study on the chemical composition of the plants in the Zizhu genus, including C. kochiana, C. integer rima, C. nudiflora, C. longipes, and C. kwangtungensis. It was found that terpenoids are widely present in this genus of plants and are the main chemical component types in the low polarity parts of this genus. Through the author’s systematic literature review and sorting, it was found that there are 131 reported terpenoids in plants of the Purple Pearl genus, including 37 triterpenes, 84 diterpenes, and 10 sesquiterpenes.
Nitric oxide (NO) is a free radical synthesized by L-arginine under the action of the nitric oxide synthase (NOS) family, and plays a role as a cellular signaling molecule in many different biochemical processes. In recent years, an increasing number of studies have shown that NO is a key biomarker of inflammatory response, playing a crucial role in the occurrence and development of various inflammatory diseases. Inhibiting excessive NO production has become an effective strategy for treating inflammatory diseases. Modern pharmacological studies have shown that terpenoids have good anti-inflammatory biological activity. In order to enrich the chemical structure types of terpenoids in Guangdong purple pearl and lay a solid material foundation for their subsequent pharmacological activity research, this article will use various chromatographic methods to separate and identify the terpenoids in the low polarity parts of Guangdong purple pearl methanol extract. In order to clarify the anti-inflammatory effects of these terpenoid components, an in vitro inflammatory model will be established by inducing RAW264.7 mouse macrophages with LPS. The anti-inflammatory effect of terpenoid components in Guangdong Purple Pearl will be evaluated using the Griess method, and the influence of terpenoid structure on anti-inflammatory activity will be preliminarily analyzed.

In this experiment, 11 terpenoids were isolated and identified from the low polarity parts of the methanol extract of the aboveground parts of Guangdong Purple Pearl, including 9 triterpenoids and 2 sesquiterpenes. Among them, compounds 1, 2, and 10 are of the lupine type, compounds 6 and 9 are of the oleane type, compounds 3-5 and 11 are of the ursolic type, compound 7 is a sesquiterpene lactone, and compound 8 is a reduced sesquiterpene. This article is the first to isolate the triterpenoid compound swinhoeic acid, which has an E-ring cleavage, from plants in the family Verbenaceae. Upon reviewing the literature, it was found that there are relatively few research reports on this compound, and it is distributed in plants of the genera Rubus, Rosa, Apocynaceae, and Potentilla in the family Rosaceae. The first discovery of this compound in Guangdong Zizhu has important guiding significance for exploring the classification of plants from the perspective of chemical structure taxonomy. On the basis of chemical component separation, an in vitro inflammatory model was established using LPS induced RAW264.7 mouse macrophages to test the anti-inflammatory activity of 11 terpenoids. The results of cell proliferation experiments showed that compounds 2 and 10 had significant inhibitory effects on cell proliferation within the range of 12.5-50 μ mol/L, while other terpenoids had no significant inhibitory effect on cell proliferation. Subsequently, compounds 1, 3 to 9, and 11 were selected for anti-inflammatory activity testing, and the results showed that compounds 3 and 9 had significant anti-inflammatory activity. The 3-hydroxyl substitution and 28 carboxyl substitution of triterpenoids were the key factors for the compounds to exert anti-inflammatory activity. The research results provide ideas for the in-depth exploration of the anti-inflammatory mechanism of terpenoids in Guangdong purple pearl, and provide experimental basis for the clinical application of Guangdong purple pearl in anti-inflammatory aspects