Studies On The Chemical Constituents And Bioactivities Of The Bulbs Of Lycoris Aurea&the Herbs Of Parasenecio Rubescens

This dissertation is composed of two parts. Chapter1describes the chemical constituents and neuroprotective effects of the bulbs of Lycoris aurea. Chapter2describes the chemical constituents and bioactivities of the herbs of Parasenecio rubescens.1. The chemical constituents and neuroprotective effects of the bulbs of Lycoris aureaThe Amaryllidaceae family, which are distributed throughout the tropics and temperate regions of the world, consists of about1,100species from85genera. Many plants from the Amaryllidaceae family are cultivated as ornamental plants, some of which have been used as folk medicines for the treatment of various diseases in many countries. In previous phytochemical studies, many alkaloids have been isolated from Amaryllidaceae plants, some of which exhibited great effects on the central nervous system and cardiovascular system. Especially an acetylcholinesterase inhibitor, galanthamine, has been used to slow down the symptoms of many nervous system diseases.Lycoris aurea is widely distributed in Hunan, Hubei, Guangxi, Guangdong and Fujian Province in China. In this paper, we describe the isolation, structural elucidation of three new alkaloids and a new flavane, along with16known compounds. The neuroprotective effects of the crude extract, alkaloidal extract and compounds L1-L13were also evaluated. Compounds L1-L7and L10exhibited significant neuroprotective effects against CoCl2-induced SH-SY5Y cell injury, while compounds L1-L5, L7, L10and L12showed obvious neuroprotective effects against H2O2-induced SHSY5Y cell death. Our results provide a preliminary indication of the neuroprotective activity in the class of Amaryllidaceae alkaloids. 2. The chemical constituents and bioactivities of the herbs of Parasenecio rubescensThe genus Parasenecio from Compositae consists of about80species in the world,51species of which are native to China. Some species of the genus have been used as folk medicines for the purposes of anti-cough, anti-bacterial infection and anti-inflammatory in China.Considering the fact that many species of the genus contain rich secondary metabolites and are proved to possess potent pharmacological activities, we examined the herbs of Parasenecio rubescens collected from Lushan mountain of Jiangxi Province in China, of which no phytochemical studies have been carried out so far. In our study, investigation on the chemical constituents led to the isolation and structural elucidation of52compounds including35new ones.Compounds P1-P42were evaluated for their antimicrobial activities against Staphylococcus aureus, Escherichia coli and Monilia albican. However, only weak antimicrobial activities were observed in compounds P13, P22, P23and P24against Staphylococcus aureus and Escherichia coli.The cytotoxicities of the extracts from P. rubescens and compounds P1-P42against B16, HepG2and MCF7cell lines were also tested. The results showed that the PE extract exhibited strong cytotoxicities in this experiment, while compounds P13, P16, P17and P40exhibited appreciable cytotoxicities.