Constituents of Pulicaria inuloides and Cytotoxic Activities of Two Methoxylated Flavonols

Plants of the genus Pulicaria are known for providing traditional medicines, spices, herbal teas, and insect deterrents. Pulicaria inuloides (Poir.). DC. is one of the less chemically studied species within the genus. Hydroalcoholic extracts from roots and aerial parts of P. inuloides were analyzed using the UHPLC-PAD-MSn technique and revealed the presence of six caffeoylquinic and eleven caffeoylhexaric conjugates together with hydroxykaempferol dimethyl ether and quercetagetin trimethyl ether. Moreover, constituents of chloroform extract from the whole P. inuloides plants were isolated and identified by spectroscopic methods. One new and four known caryophyllene derivatives, three thymol derivatives, and four polymethoxylated flavonols were found in the analyzed extract. The structure of the new compound was established by spectroscopic methods (HRESIMS, H-1 NMR, C-13 NMR, COSY, HSQC, HMBC, NOESY). The cytotoxicity of 6-Hydroxykaempferol 3,7-dimethyl ether and quercetagetin 3,7,3'-trimethyl ether (chrysosplenol C), which are major flavonols isolated from the plant, were tested on prostate epithelial cells (PNT2), prostate cancer cells (DU145 and PC3), human keratinocytes (HaCaT), and melanoma cells (HTB140 and A375). Both flavonols demonstrated moderate cytotoxic activity against PC3 cells (IC50 = 59.5 mu M and 46.6 mu M, respectively). The remaining cell lines were less affected (IC50 > 150 mu M).

Automated summary

Plants of the genus Pulicaria are valuable for their traditional medicinal, culinary, and insect-repelling properties. A specific species within the genus, Pulicaria inuloides, has been less studied chemically. By analyzing hydroalcoholic extracts of the roots and aerial parts of P. inuloides, it was found to contain several caffeoylquinic and caffeoylhexaric conjugates, as well as hydroxykaempferol dimethyl ether and quercetagetin trimethyl ether. Additionally, chloroform extracts from P. inuloides plants revealed the presence of caryophyllene derivatives, thymol derivatives, and polymethoxylated flavonols. The cytotoxicity of two major flavonols isolated from the plant, 6-Hydroxykaempferol 3,7-dimethyl ether and quercetagetin 3,7,3'-trimethyl ether, were tested on various cell types with moderate activity against prostate cancer cells.